Should We Ban This Chemical?

December 7, 2022


While walking through a store the other day, I came across a “toxic” chemical for sale.  From previous reading, I knew that it was responsible for a number of adverse events, such as death due to accidental inhalation, severe tissue damage after prolonged exposure to its solid form but serious burns from its gaseous form, and a number of unpleasant though not typically life-threatening side-effects from excessive ingestion.  I also knew that this chemical is a major component of acid rain, contributes to soil erosion, leads to corrosion and oxidation of many metals, contaminates electrical systems which often causes short-circuits, and decreases effectiveness of automobile brakes.  It has also been found in biopsies of pre-cancerous tumors and lesions.
The chemical?  Dihydrogen monoxide (DHMO).  It is also known as dihydrogen oxide, hydrogen hydroxide, hydronium hydroxide, or simply hydric acid. Part of this chemical is the highly reactive hydroxyl radical, which can mutate DNA, denature proteins, and disrupt cell membranes in our bodies. The atomic components of DHMO are found in a number of caustic, explosive and poisonous compounds such as sulfuric acid and nitroglycerine.
Some folks might wonder why this chemical has not been banned from sale already.  Myself?  I just walked on by.  I normally do not spend money on this chemical since I have plenty already in my home.
However, as bad as this chemical can be made to sound, it actually is quite harmless when we are exposed to its safe level.  In fact, DHMO is also known as water, that is di-hydrogen (H2) mono-oxide (O).  It is essential for nearly all life on planet Earth, as all of us already know.  But like any chemical, water can be toxic if you drink too much of it at one time, and of course, we all know that accidental inhalation of water, or skin contact with ice or steam can cause harm.

The media will often talk about chemicals in a way that makes them sound scary.  And indeed some chemicals are quite toxic in small amounts and we should all be careful when we use chemicals around the house for cleaning or pest control, making sure that we follow the label and keep these products out of reach of our children.  But a description of a chemical’s toxic effects, without an understanding the dose to which one might be exposed, is not helpful.  A liter of botulinum toxin, the most toxic chemical known to humans, will kill most of the humans on planet Earth, yet we used this same chemical to treat wrinkles and migraine headaches in incredibly tiny doses.  As toxicologists are fond of saying, it is the dose that makes the poison.  Reciting a scary list of possible effects from a chemical exposure, without indicating what the exposure might be, is not good science or journalism.

So how might one go about and determine a level of chemical exposure?  A good rule of thumb here is to take the smallest sugar granule you can see from a sugar packet.  It weighs about 50 micro-grams.  If you put this sugar grain into a liter of water it becomes about 50 parts per billion (or ppb).  This is not a lot, but gives you a sense of a chemical level.  Many chemicals are safe at this level.  For a listing of safe levels of various chemicals see: https://iter.tera.org.

It is impossible to live in a world without chemicals. So be informed, and make sure you drink plenty of DHMO!




Is that Benefit Worth its Risk?

November 9, 2022


As we all know, life can be complicated.  Tools that are very useful for gardening, like a rake, can hurt pretty badly if stepped on the wrong way.  This useful/hurtful idea extends to nearly all aspects of our lives.  We can all think of numerous examples of this idea, like cars, electricity, or lawn mowers. This idea of useful/hurtful or benefit/risk also extends to chemicals, the most common ones to which we willingly expose ourselves are foods of various sorts.  And while most of us can eat many foods in moderation without too many problems, we likely all know of folks with food allergies, some of which can be life threatening.

So how does one look at the useful/hurtful or benefit/risk for chemicals?  In some cases, it’s easy.  Everyone needs to drink dihydrogen monoxide (yep that’s water), or at least drink other fluids that contain a lot of water, like coffee, milk or beer.  But we all know that one can drink too much water leading to a disturbance in nerve function; or too much coffee leading to irritability and heart palpitations; or to much milk leading some to have digestive problems; or too much beer leading to intoxication.   In such cases many of us will naturally limit our consumption to gain the benefit of the chemical, but avoid the risk.  In fact, this risk/benefit comparison is a common approach with exposure to many chemicals in our lives, or with other non-chemical aspects, such as that pesky garden rake.

We are exposed to tens of thousands of chemicals every day.  You cannot escape this exposure! Coffee has over 1000 chemicals, the principle one being water.  Our various foods contain just as many chemicals, and perhaps even more.  Our houses and farms also contain numerous chemicals, and many, if not all, have huge benefits.  For example, I grew sweet corn this year in a different patch of my garden.  I hand weeded this corn 3 times.  Despite this effort the weeds grew to be taller than my corn and my ears were correspondingly smaller than last year.  My cousin grew sweet corn as well but sprayed Round-up where the corn had been planted before the corn emerged.  Voila, fewer weeds; bigger ears of corn (and of course, bragging rights to my cousin). Even organic farming, which eliminates or greatly reduces the use of chemicals, has drawbacks such as increased in use of machinery, labor, fuel and emissions.  Organic farming typically produces less food, at higher price, and which has been shown to not be any more nutritious than non-organic food. 

So how do we make this benefit/risk comparison with chemicals other that those found in drinks and food.  The easiest way is to read the label of the chemical of concern, and importantly, follow directions (I know, guys, this can be hard to do.)  A little bit of Round-up is good, so more is better, correct?  Wrong.  Follow the directions on the label.  Industry and government scientists who study the risks of such chemicals have worked very hard to get the safety right and make the directions on the labels adhere to this safety work. We can all thank them by following the directions on the label.

Well what about all those chemicals we hear about in the news; they do not all have labels, correct?   Correct, not all chemicals in the news, like ethylene oxide (a medical sterilent about which I have written before) or the “forever” chemicals (the most talked about one is perfluorooctanoate (PFOA) have labels.  However, government scientists also work hard to set safe levels for these chemicals, and afterwards rules for how much can be found in our products. Although more uncertainty exists in this process, since the underlying data are often not as extensive as with chemicals that have labels.  If you have questions about chemicals in the news, feel free to send them to me.  I would be happy to try and answer them.

In the meantime, let’s all enjoy the many benefits that chemicals bring us, follow the labels when they are available to avoid their risks, and ask questions of appropriate experts when you are uncertain about how to proceed.




Cancer Causing Chemicals is Sunscreen? Oh my!

October 3, 2022


While skimming through our morning news, we came across a story on the internet about a chemical known to cause cancer found in one or more sunscreens. Interesting, we thought, do we not use sunscreens to prevent cancer?  Once again, the quote, often attributed to Mark Twain, came to mind, along the lines of if you want to stay sane one should give up reading.  But against this better judgment we continued.

The chemical was benzene and we both knew it to be associated with blood cancers in people.  So that part of the story was correct.  But rather than panic, and stop using our sunscreen, we looked for information on how much benzene was present.  After all, if we were using sunscreen to keep from getting cancer, then we needed to compare this benefit to the risk of cancer from benzene, and for that we needed to know how much benzene was in the sunscreen.  This benefit-risk comparison is not unlike what many of us do every day (driving a car versus walking to the store).  We kept in mind that the potential harm from any chemical, referred to as its hazard, only occurs IF the amount of exposure is high enough, and often enough.  Most chemicals, like the one described in our morning news, can be made to sound very scary to all of us.  Carcinogen is one of the hazards many fear the most, us included, and using it in a headline is guaranteed to get people’s attention, Mark Twain’s alleged statement not withstanding. 

So,what about the level of benzene in our sunscreens?  Based on the reports of the levels of benzene that we’ve seen, the risk of cancer appears to be extremely low and well within the levels of risk that are found to be acceptable by regulatory agencies around the world.  These estimated risks are extremely small and may even be zero.  Moreover, the US FDA (Food and Drug Administration) used a science-based process to determine that the given amount of benzene would cause little to no harm.  However, do we believe that the FDA should do nothing about the potential sources of benzene in sunscreen? Not at all.  Benzene is a contaminant resulting from making the sunscreen and serves no functional purpose.  Its presence in sunscreen is causing fear from use of a product that has a clear health benefit:  PREVENTING SKIN CANCER FROM TOO MUCH SUN EXPOSURE.   Yet another classic example of why we need a risk assessment.  Bottom line – the benzene level in sunscreen is extremely low and within the acceptable levels of already very low risk; the sunscreen, used correctly, helps prevent skin cancer.   You make the choice.  Us?   We’ll enjoy the rays and slather on the sunscreen.

By Michael Dourson and Jay Gooch.  Dr. Gooch is a toxicologist retired from Proctor and Gamble in Cincinnati, Ohio and Vice President of the Toxicology Education Foundation.




Chemicals by Land, by Sea, and in our Bodies?

September 22, 2022


It may come as a surprise to many of us, but several chemicals of industrial use are also made on a routine basis inside our bodies, of course in a much smaller amount.  For example, ethylene oxide is used as a disinfectant to kill bacteria and virus on surfaces of hospitals.  It has the added feature of being a dry gas, so it can be used to sterilize certain medical equipment, such as blood transfusion tubes, that are otherwise difficult to keep free of pathogens (I have written about this chemical before as shown here).  Another chemical of huge industrial use is formaldehyde. Yes…that same chemical that was used to preserve the frog specimens that many of us studied in high school/college biology classes. Turns out that formaldehyde is extremely useful in making a number of other important chemicals, and yes our bodies make a small amount of it every day in our normal metabolism.

Aren’t these chemicals toxic?  Of course they are!  All chemicals are toxic AT SOME LEVEL.  Ethylene oxide and formaldehyde cause tumors at high concentrations in experimental animals, and there is some evidence that they cause tumors in humans.  However, levels causing these tumors are well above those that are bodies make daily, and industries making or using these chemicals protect their workers by establishing thresholds for safety, and include protective equipment.

Can the public be exposed to levels of ethylene oxide or formaldehyde that might cause us harm?  Generally no.  The levels of either of these chemicals in the environment more or less matches levels found in each of our bodies, so getting exposure to levels that can cause us harm is very unlikely.  However, the U.S. Environmental Protection Agency has recently reaffirmed a previously established safe level of ethylene oxide and proposed a safe level of formaldehyde that are WELL BELOW what our bodies make every day.  These levels are overly safe, and as a result call into question the process by which our EPA developed these estimates. For example, the overall impression of EPA’s current draft is that formaldehyde is toxic at levels below what is often found indoors or in outdoor air.  Perhaps not surprisingly, many scientists disagree with EPA.

In fact, it is difficult for many of us to understand how EPA can propose safe levels for chemicals that are lower than levels that occur naturally or are produced in our bodies every day.  It certainly is not because they do not have the good scientists. Dr. Rory Conolly, one of several of EPA’s former scientists who won the Lehman award from the Society of Toxicology (an award sometimes referred to as the Nobel prize for risk assessment), has published extensively on formaldehyde and is heavily cited in EPA’s text. However, Dr. Conolly disagrees with the current EPA position.  EPA should listen.

EPA’s safety level for formaldehyde is still a draft.  So what might EPA do to improve it?

First, EPA should focus on formaldehyde’s first toxic effect, which is tissue irritation. Estimating a safety level for other effects does not make sense, since all of these other effects are higher, and by definition the safety level based on irritation will protect against them.  Second, EPA should follow its own guidelines for assessment of tumors and develop a safety level based on the way in which formaldehyde causes these tumors at high levels. Dr. Conolly suggests an approach that might work very well. Finally, EPA might consider new information from a recent scientific workshop that showed formaldehyde cannot penetrate the cell at low concentrations.  This finding supports the threshold approach adopted by the European Union t al. (2020). 

It is certainly confusing that EPA proposes safe levels of these chemical that are below what our bodies makes every day.  This makes it harder to trust other EPA assessments, many of which are very good.




Should We Ban This Chemical?

August 3, 2022


While walking through a store the other day, I came across a “toxic” chemical for sale.  From previous reading, I knew that it was responsible for a number of adverse events, such as death due to accidental inhalation, severe tissue damage after prolonged exposure to its solid form but serious burns from its gaseous form, and a number of unpleasant though not typically life-threatening side-effects from excessive ingestion.  I also knew that this chemical is a major component of acid rain, contributes to soil erosion, leads to corrosion and oxidation of many metals, contaminates electrical systems which often causes short-circuits, and decreases effectiveness of automobile brakes.  It has also been found in biopsies of pre-cancerous tumors and lesions.

The chemical?  Dihydrogen monoxide (DHMO).  It is also known as dihydrogen oxide, hydrogen hydroxide, hydronium hydroxide, or simply hydric acid. Part of this chemical is the highly reactive hydroxyl radical, which can mutate DNA, denature proteins, and disrupt cell membranes in our bodies. The atomic components of DHMO are found in a number of caustic, explosive and poisonous compounds such as sulfuric acid and nitroglycerine.

Some folks might wonder why this chemical has not been banned from sale already.  Myself?  I just walked on by.  I normally do not spend money on this chemical since I have plenty already in my home.

However, as bad as this chemical can be made to sound, it actually is quite harmless when we are exposed to its safe level.  In fact, DHMO is also known as water, that is di-hydrogen (H2) mono-oxide (O).  It is essential for nearly all life on planet Earth, as all of us already know.  But like any chemical, water can be toxic if you drink too much of it at one time, and of course, we all know that accidental inhalation of water, or skin contact with ice or steam can cause harm.

The media will often talk about chemicals in a way that makes them sound scary.  And indeed some chemicals are quite toxic in small amounts and we should all be careful when we use chemicals around the house for cleaning or pest control, making sure that we follow the label and keep these products out of reach of our children.  But a description of a chemical’s toxic effects, without an understanding the dose to which one might be exposed, is not helpful.  A liter of botulinum toxin, the most toxic chemical known to humans, will kill most of the humans on planet Earth, yet we used this same chemical to treat wrinkles and migraine headaches in incredibly tiny doses.  As toxicologists are fond of saying, it is the dose that makes the poison.  Reciting a scary list of possible effects from a chemical exposure, without indicating what the exposure might be, is not good science or journalism.

So how might one go about and determine a level of chemical exposure?  A good rule of thumb here is to take the smallest sugar granule you can see from a sugar packet.  It weighs about 50 micro-grams.  If you put this sugar grain into a liter of water it becomes about 50 parts per billion (or ppb).  This is not a lot, but gives you a sense of a chemical level.  Many chemicals are safe at this level.  For a listing of safe levels of various chemicals see: https://iter.tera.org.

It is impossible to live in a world without chemicals. So be informed, and make sure you drink plenty of DHMO!




Follow the Science?

July 6, 2022


“Follow the Science” is a phrase occasionally heard from our family and friends, and signs found in yards throughout various neighborhoods often state “Science is Real,” followed by “Water is Life.”  So what exactly does this mean?   Water certainly is an essential to life in our world, yet when we drink too much, water acts as a neurotoxin that can lead to death.  So science says water is good but the science of toxicology says it can also be bad.  Science really says it is the LEVEL of exposure that makes the difference.


The science of toxicology deals with exposure to levels of chemicals.  Remember – LIFE IS CHEMISTRY.  We are exposed to tens of thousands of chemicals every day, and most are naturally occurring and some even necessary.  In fact, ALL chemicals are toxic at some level – even water, as noted above.  So it comes down to the exposure that determines the toxicity, and all chemicals have a level with little or no toxicity.


Mercury in fish, for example, is naturally occurring.  All fish in the world have some level of mercury (and of course may have more as a result of environmental pollution).  Eating fish is very good for you; therefore, dietary guidelines are set to limit our exposure to mercury to below its safe level.  [Dietary guidelines provide advice on what to eat and drink to meet nutrient needs, promote health, and prevent disease]. Lead is another example of a naturally occurring chemical.  However, we all know or have heard of the medical problems associated with too much lead from contamination.  Here again, the exposure makes the difference.  Ever heard of formaldehyde?  If you ever dissected a frog in biology class, you most likely have smelled it.  Guess what? Your body makes it every day.  Yep, another naturally occurring chemical that is toxic at high levels, but which also has a safe level.

So when you hear someone claiming a particular chemical is toxic, ask yourself two questions.  First, who is making the statement? A TV host, a news reporter, a lawyer, a physician, or a scientist with expertise in toxicology?  Take time to consider the background of the person making the statement.   Just as you wouldn’t go to a lawyer for advice about your swollen ankle, why would you make a judgment on a chemical without getting the facts from a toxicologist?

Second, find out “how much is the exposure?”   A good rule of thumb here is to take a sugar packet, dump it out on the table, and find the smallest sugar grain you can see.  Wet your finger and pick it up.  Then put this sugar grain into a liter of water.  The sugar grain weighs about 50 micro-grams.  When you put this into the liter of water it becomes about 50 parts per billion (or ppb).  This is not a lot, but gives you a sense of a chemical level.  Many chemicals are safe at this level.


So should we follow the science?  Of course!  But make sure that the statements made regarding the toxicity of chemicals are from toxicologists, or that reporters sharing such information reference these experts.  Otherwise, we are likely to stop eating some of our favorite foods, like lake Erie perch, a healthy part of any diet, because of misinformation.  Or we are likely to stop using very helpful products, like lead batteries that start our cars, because of misguided fear?  It is impossible to live in a world without chemicals. So be informed.  That is following the science.





June 7, 2022


At one or more times in our life we are all likely to end up in a doctor’s office or hospital for a medical procedure.  Or we may decide to give blood so that someone else’s life can be improved, or even saved.  Often medical staff will use equipment to monitor our symptoms or to take measurements.  Sometimes this equipment is used only once, like gloves, but often it is reused, such as stethoscopes or scalpels.

So how does the medical community keep this equipment free of contaminating bacteria, viruses and fungi?  Through sterilization!  All of the various medical tools or equipment used in doctors’ offices or hospitals are routinely sterilized, either by wiping down surfaces with disinfectants, reusing medical tools after heating to a level that kills such organisms, or using equipment only once.  All of these processes work and are an important part of keeping us safe.  However, even the one-use equipment must be sterilized beforehand.  So how does this get done?

Several ways exist to sterilize one-use medical equipment, such as using radiation, or heat, or a disinfecting chemical such as ethylene oxide.  Each of these ways has advantages and disadvantages.  For example, the plastic tubes that are used to administer blood and saline to many of us cannot be sterilized by heat or radiation, since this would generally melt the plastic.  In such cases ethylene oxide is used since is it dry, penetrates the openings in the plastic, and leaves little to no residue.  In other words, ethylene oxide and similar disinfectants are invaluable tools in keeping people safe and free of infections from potentially unsanitary medical equipment,

As you might imagine, the use of disinfection also comes with a risk (just as not using disinfection comes with a risk!) In the case of ethylene oxide, the risk is the development of cancer but only at very high exposures, well beyond what you might get from hospital equipment. As I have stated before, government agencies work very hard to develop safe levels for chemicals like ethylene oxide, that is, levels that will cause little, if any cancer, but that would still allow the use for medical sterilization.  Not surprisingly, the U.S. Environmental Protection Agency (EPA) developed a safe level of ethylene oxide in 2016 that I reviewed for them.  However, many folks are now re-reviewing this EPA value because new information shows that our bodies actually make a small amount of ethylene oxide every day, just from normal metabolism.  Ripening fruit also emits the gas ethylene, a small amount which our bodies covert to ethylene oxide.  Fortunately, these amounts are well below any level shown to cause cancer.

This new knowledge suggests that EPA’s older level was overly safe (not a bad thing), but using it now suggests us getting more cases of a specific kind of cancer than actually found in our population.  A more recent government assessment by the Texas Commission for Environmental Quality analyzed this new knowledge and proposed a much higher safe level than EPA.  Texas’ value is still safe and also consistent with what our bodies make every day. Other groups, such as the U.S. Food and Drug Administration, have also reviewed this new knowledge and came to roughly the same conclusions as Texas.

Because of these different estimates of safe levels and the intense need for medical sterilization during the COVID pandemic, ethylene oxide has been in the news.  Its use in medical device sterilization facilities has often been misunderstood as a threat to public health because of the cancer finding at very high exposures.  In part, this misunderstanding is…understandable, especially in light of the EPA’s older assessment that we now know did not fully account for our bodies’ own production of ethylene oxide or its prevalence in the environment from many other sources. 

So will EPA use this additional information and modify its safe level?  Perhaps.  EPA could easily say that their older assessment was the best they could do at the time (I reviewed it for them so this is true), say correctly that new data have since been published, and then state that Texas has done a good job of standing on its shoulders and going the next step to a more scientifically accurate, but still safe level of EtO exposure.
But if EPA does not, this we do know: ethylene oxide does an excellent job in cleaning medical equipment; our bodies make it daily at levels that are well above EPA’s older safe level; and we are exposed to natural levels of it from sources other than the medical sterilization plants. Furthermore, the pandemic has shown us how important the need is for sterilized medical equipment.  Nor is it reasonable to label human breath as hazardous as a Superfund waste site, which is the practical implication of continuing to use EPA’s older safe level.

Michael L. Dourson, Ph.D., DABT, FATS, FSRA
President and Director of Science



Banning Pesticides: Is This in the Public's Best Interest?

May 2, 2022


Farmers routinely use pesticides, whether organic or not, to control insects and weeds on our crops.  This often results in pesticide exposures to our farmers, and occasionally to us when a little bit of pesticide remains on the crops after harvest.  However, when the pesticide is used according to its instructions, the safety of our farmers and ourselves is assured due to the extensive testing by industry (millions of dollars in studies) and review by government scientists, many of them who are doctorate-level and board-certified toxicologists.  We, the public, also get the benefit of increased crop yields, which usually translates into lower food prices and the benefit of product availability. 

So is banning pesticides in the public’s best interest?  The answer is an emphatic yes when the science indicates that exposures are not safe.  But does good science always get used in making decisions?  Fortunately the answer is nearly always yes, with some exceptions.  For example, EPA recently banned all uses of the pesticide dursban (also know as chlorpyrifos). This was despite the fact that EPA scientists determined that levels of dursban were safe on many crops when used according to its directions, even for sensitive humans and children.  This ban prompted a lawsuit by a number of food producers for soybeans, sugarbeets and cherries asking EPA to follow the findings of its own scientists.  Why?  Well the State of Michigan grows a majority of U.S. tart cherries and a good portion of U.S. sweet cherries, and dursban is considered to be critical to the Michigan cherry industry as there are no alternative pesticides that effectively control trunk borers.  Those of us who have tried to grow apples, pears or peaches without the aid of spaying our trees---and ending up with little to no edible fruit---can certainly relate.  So to the Michigan cherry famers, EPA’s ban might be Cherry-O…

But why would EPA ban all uses of dursban when its own scientists said many of its uses were safe?  The answer, as are many, is complex.  But one reason is not the lack of qualified staff.  EPA has highly credentialed staff, more so than many other organizations.  One of the reasons might have to do with environmental activists who want to ban all pesticides that cause toxicity to the nervous system of insects, and also in humans that get exposed from improper use.  If dursban exposures were actually causing harmful effects at EPA’s determined safe levels, this would be entirely appropriate.  But this is likely not the case as one recent scientific publication suggests.

So again, should we worry about pesticides to which we are daily exposed?  Well, it all depends on how much of the exposure one gets, as previously described.  Too much of any one thing is likely not to be good for us.  This includes pesticides, like dursban, but also other natural, organic and conventional pesticides.  However, government agencies work very hard to keep us safe.  Follow the labels on the various chemical products to stay safe, use products in moderation, and of course follow the science.


The Chemicals All Around Us?

April 2, 2022


We often hear folks talk about wanting to live a chemical-free life, or at least one associated with only natural chemicals.  This talk often centers around the use of pesticides, a type of chemical used for killing pests that otherwise destroy or contaminate our food.  For example, some folks rave about food grown organically, erroneous thinking that NO pesticides were used in its production, whereas food grown with conventional pesticides is less healthy.  But is there really a difference between organic and conventional pesticides?  Is it really possible to live without chemicals?

The short answer to the last question is an emphatic no.  Life is chemistry.  We are all exposed to tens of thousands of chemicals every day, the vast majority of them naturally occurring.  A cup of coffee, for example, has about 1000 chemicals, the primary one being dihydrogen monoxide (H2O or water).  A potato likely has just as many chemicals, including the naturally occurring pesticide solanine.  This latter pesticide is the reason that eating potato leaves or the green parts of potatoes will make many people sick.  Not surprisingly, the part of the potato that is not green, the part that most of us eat, also includes the natural pesticide solanine, but at a level that is lower than a toxic level.  So we do not need to worry about eating potatoes even though they contain a lot of chemicals, including its natural pesticide.   In general, plants routinely make their own pesticides from naturally occurring chemicals to protect themselves from pests or to eliminate competition.  Anyone trying in vain to grow tomatoes underneath or near walnut trees will know this to be true.  The chemical juglone, a naturally occurring pesticide, is highly destructive to sensitive plants, like tomatoes.

So is it better to eat only organic produce? Not at all.  Much of the information about pesticides one can find from websites is one-sided, describing hypothetical dangers of low levels of synthetic pesticides, and showcasing organic farming as a pesticide-free alternative, which it is not.  In fact, organic farming often results in more insect damage, which in turn causes the crop to make more of its naturally occurring pesticide. It is important to remember that each pesticide, whether organic or conventional, is intended to kill pests. The only overall difference in organic and conventional pesticides is that organic pesticides generally come from natural sources.

So should we worry about chemicals to which we are daily exposed?  Well, it all depends on how much of the exposure one gets, as previously described.  We can all be exposed to some chemicals in large amounts, like water, and still be safe, or mixtures of chemicals that make up most of our foods.  But we all know that too much of any one thing is likely not to be good for us.  This includes natural and conventional pesticides as well as many household products.  Government agencies work very hard to keep us all safe.  Following the labels on the various chemical products we use is a good start to a safer life.



PFOA: The Forever Chemical?

March 3, 2022


You probably have heard a lot about the chemical PFOA (perfluorooctanoate), sometimes called the “forever” chemical.  PFOA is a simple 8-carbon molecule that has fluorine atoms attached rather than hydrogen atoms. As a result PFOA resembles several fats found naturally in our bodies, but it does not break down to any significant extent.  Although PFOA does not occur in nature, it is a very useful tool for firefighters in putting out electrical and oil fires that cannot otherwise be doused with water.  And  because it is chemically stable it has been used in a variety of household products, such as carpets and food wrapping.  Due to its extensive use in so many areas of our lives, very low concentrations are found in our bodies, our houses and our environment.  In a few places, these levels may be harmful.

This chemical has been studied A LOT, and for all the study, a big problem has emerged:  There are large differences in government opinions as to what the safe level of PFOA actually is according to recent international meeting.  Sometimes these differences are as much as 750-fold.  These differences are principally due to two issues.  First, the determination of PFOA’s safe dose depends, in part, on establishing its first toxic effect in experimental animals, such as a change in liver enzymes, and government agencies, even within the US disagree. Second, the time it takes for PFOA to leave our bodies is generally much longer than that measured in experimental animals.  This longer half-life lowers PFOA’s safe dose estimate for us.

This is a prime example of what environmental risk assessment is all about.  PFOA is an important and very useful chemical, particularly for firefighters, but as with any chemical, too much may be harmful.  Do we eliminate the products and its use in electrical and oil fires, or try to determine, collectively, a safe level for our environment?  Trying to determine a more uniform safe level seems to be the better course.  However, this is a difficult task, and so it would make sense that governments and other organizations work together to accomplish this goal. 

Recently, an international scientific collaboration has resulted in a consensus position on the time required for half of the PFOA to leave our bodies, and it is not nearly as long as other groups think. This is good news, but like any science, this consensus needs to undergo peer review during submission for publication later this month. In the meantime, this consensus may alleviate part of the differences in opinion among government groups and lead to more uniform estimates of PFOA’s safe dose.  Additional collaborative work should also be started in other areas of scientific differences.



RoundupTM: Are we safe from its exposure?

February 6, 2022


All of us have likely seen the advertisements on television offering legal counsel for individuals who might have had exposure to the herbicide RoundupTM and have certain cancers.  These ads are based on a court ruling in California, which was based in part on publications that purport to show links between cancers and hormone-related effects. Others have opined that the U.S. Environmental Protection Agency (EPA) is not doing its job in protecting the US public from the dangers of glyphosate, the active ingredient of this herbicide. So natural questions for any of us to ask might be:


  • Are the EPA and big agricultural groups defending glyphosate because they need to maintain business as usual?
  • Should the public be concerned about cancer and hormone effects from RoundupTM?


The short answer to either question is an emphatic NO.  EPA and health agencies around the world have reviewed hundreds of experimental animal and human studies on glyphosate and come to a near unanimous conclusion:


  • RoundupTM does not cause cancer and, when used according to directions, is safe at the occasional, tiny levels found in our food. 


For example, the U.S. Department of Agriculture (USDA) released a 2016 report that found no pesticide residue levels high enough to pose any human health risks, even for infants. Specifically, the USDA tested for pesticides in 10,619 samples of food.  Pesticide residue levels were found to be at or below tolerance levels set by the EPA in all but 0.4% of the samples.  Importantly, tolerances would have to be exceeded routinely for nearly a lifetime for any possible health effects in the most sensitive members of our public---a very remote possibility.


The one exception to the otherwise unanimous conclusion on the safety of RoundupTM by US and other health organizations was that drawn by the International Agency for Research on Cancer (IARC) in France.  Importantly, judgments by this group are not peer reviewed.  Other items included in IARC classifications are eating red meat, exposure to emissions from high frying temperatures, and working as a hair-dresser or barber.  


So why is IARC’s judgment different than all other organizations? 


IARC classifications are based primarily on a chemical’s “hazard” potential, and do not generally consider the dose at which effect can occur.  This IARC approach differs greatly from the “real world” conclusions drawn by multiple international regulatory agencies that RoundupTM exposure at current levels does not cause cancer in humans.  Moreover, the IARC approach ignores one of the key principles of toxicology---that all chemicals are toxic at some dose, yes, even water.  So making statements of health risk without accounting for the dose causing the health effect is not good toxicology, nor good medicine.


For additional reading on the supposed risks from RoundupTM and for links to stories about its well-known benefits, especially to the farmers in our area and around the world, please see well-balanced essays here and here.



Reader Question: Flame Resistant Pajamas?

January 3, 2022


Reader Submitted Question:  I recently bought polyester flame resistant pajamas because my daughter is in an in-between size stage. The doctor’s office said she either needs to wear the flame resistant or tight fitting cotton non-flame resistant. The issue is that there isn’t a current cotton size that would comfortably be snug on her. What would you recommend?

 Response:  The fit, style and type of material are all important in safety considerations in choosing children’s pajamas.  Specific concerns include fire prevention, the treatment of sleepwear with flame-retardant chemicals, and choking hazards. Cotton is one of the most commonly used fabrics for children’s sleepwear. Cotton sleepwear is recommended to fit snugly to reduce choking hazards and flammability, as tighter clothes are less likely to cause choking and, because they do not trap as much oxygen as looser fitting clothes, are less likely to catch fire.  Polyester is the other major fabric used for children’s sleepwear.  It has naturally ‘built in’ flame retardants, where the flame retardant is inserted into the fabric fiber and considered chemically stable.  Because the garment is not treated directly it is a popular fabric choice for large manufacturers of sleepwear.  Some synthetic fabrics (nylon and acetate, appears similar to silk) may be treated with additional flame retardants, but they must still follow the United States Consumer Products Safety Commission (CPSC) regulations on the use of flame retardants in children’s garments.  If information is not given on the garment’s tag, such as “chemically treated”, you can contact the manufacturer and inquire about the chemicals used in the treatment.    

Unfortunately, the risk of fire and burns versus the risk of toxic chemical exposure is one that must be weighed individually by the parents. However, the use of flame retardants will always slow, and sometimes prevent, a fire.  The health risk from flame retardants is real but only observed at very high exposures—much higher than found in pajamas.  And, of course, always keep kids away from matches, candles, and cigarettes.




The "Dirt" on the Safety of Detergent Packets:


December 9, 2021


As parents and grandparents of young children, we should always make ourselves aware of new potential hazards that we bring into our homes. Some of us may even have called the local poison control center with various concerns over some items (1-800-222-1222).


Several studies have been published that compared child exposures to laundry and dishwashing soaps and to packets of either one.  It has been shown that twice as many children are exposed to these soap packets than the regular laundry and dishwasher soaps and the children exposed to the soap packets experienced more severe health effects.  The data used for these studies were extracted in part from the National Poison Data System (NPDS) for reported exposures for children under 6 years old from 2013 through 2014.

The information on the safety of these laundry and dishwasher soap packets has prompted many companies that manufacture these products to change the packaging to make them less attractive to young children.  For example, a bitter taste has been added to the outer part of the packet to deter children from keeping the packets in their mouths.  Additional features have been added, such as containers with child-proof lids.  As always, warning and product labels should be read and followed by parents and caregivers of children.

So, where are your laundry detergents kept?  Are they out of reach? Are you confident they can’t be accessed by an enterprising child with a talent for climbing? 


Please make sure these dishwasher and laundry detergents, and all of your cleaning supplies, such as floor cleaners, disinfectants, and hand sanitizers, are stored in a secure place out of the reach children.

The experts at poison control centers also urge parents and caregivers to:

  • Always keep cleaning agent containers closed or sealed, and stored out of the reach of children.
  • Follow the instructions on the product label.
  • Call your local poison center at 1-800-222-1222 immediately if you suspect a child has come in contact with this detergent.


For Additional information please see:



Understanding Asthma – and its causes:

November 5, 2021



Since 2001, the total number of people with asthma has increased from 7% to 8% in the U.S, with children being diagnosed with at slightly higher levels. As a parent, this is a huge and worrisome number. 



So what is asthma?



Asthma affects the respiratory system, causing the airways to become narrow, which limits the amount of air we can breathe into our lungs. Sometimes this narrowing makes our cells produce more mucus, which further limits airflow. A person with asthma will have shortness of breath, and perhaps wheeze, cough, and have chest tightness.  Sometimes asthma ends on its own, but often it requires treatment with medication through an inhaler to open the airways. Some asthma attacks can be severe and require emergency treatment. Although asthma appears to be a lifelong disease, it can be easily controlled by medications that prevent an attack or reduce symptoms, or by avoiding by things that may trigger an attack.  So what causes asthma?



Asthma is linked to a number of common household allergens and irritants, like pet fur and dander, dust, cigarette smoke, mold, and pollen. A number of other common pollutants found in the air can also cause asthma, such as ozone and car exhaust. Respiratory infections as an infant or in early childhood can also cause asthma. Asthma may also be genetic.  Well, what about hairspray and cleaning products? 



Some research says that cleaning products may cause wheezing in young children. Another study even suggests that exposure before birth, or during pregnancy, may increase your kids’ risk of wheezing. Unfortunately, most studies cannot link one individual chemical or product to the increase in wheezing or asthma-like symptoms. And although we can rely on animal research to get this kind of information, animals are frequently exposed to extremely high concentrations, which do not represent everyday human exposures. In contrast, regular cleaning reduces the presence of known allergens and irritants mentioned above, and has been shown to reduce allergy and asthma symptoms.  There are many sites on the internet that provide lists of chemicals and other items that supposedly cause asthma, but not all of these sites are reliable. If you are interested in seeing if a particular chemical might cause asthma, we recommend visiting the website of the Association of Occupational and Environmental Clinics that has a searchable database (http://www.aoecdata.org/ExpCodeLookup.aspx).  A final note on causation, more recent research suggests that being TOO clean may actually increase your child’s risk of developing asthma. Huh? In fact, the modern world has greatly increased standards of hygiene and sanitation over the years, thereby reducing the rates of disease and increasing overall health.



That’s great, right?  Maybe not!



This research, referred to as the “Hygiene Hypothesis,” suggests that because our better sanitation and hygiene has decreased the number of infections that our kids get, this hasactually caused an increase in asthma. Why? Because infections allow our immune systems to develop properly, and thus any reduction in childhood infections may actually make kids MORE at risk for allergy and asthma. Not surprisingly, the use of antibiotics in early childhood is also linked to childhood asthma and allergy problems, and maybe for the same reasons. We are not allowing our kids to recover from their own infections by themselves, which would strengthen their immune systems. 



So are kids getting asthma because of too many allergens or household chemicals? Or because they are not getting exposed to enough dirt? There is no real answer yet.  But in the meantime, the US EPA suggests that improving household air quality can drastically reduce asthma and allergy symptoms (http://www.epa.gov/iaq/pubs/careforyourair.html).


Michael Dourson and Melissa Vincent



Reader's Question:

October 8, 2021


I have a seven month old and a trying to find information if items made from or with polyurethane are safe. My initial concern came after purchasing a piece of small furniture for the nursery where the odor was unbearable. The product was made from polyurethane foam and covered in polyester. I researched and found different results indicating it was or was not safe to expose your child to these products because of the smell and the toxic chemicals the products are made with. Is this true? If I can’t smell the chemical, is it still dangerous?  Also, are there different types of polyurethane? I would like as much information on the subject as possible please, as I have found many products do have polyurethane in them.


Thank you





Dear Jaime

Thanks so much for your question. It is important for parents to be vigilant regarding their children’s health. Usually, if you can smell one or more chemicals coming from any consumer product, this indicates that the product is releasing a small amount of chemicals that are volatile, that is they are easy emitted to air. Usually, a stronger smell is associated with a higher level of these chemicals in air. At some level, you or your child might experience irritation or minor health effects, such as coughing. However, sometimes the levels are high enough that more severe health effects occur, such as trouble breathing, headaches or dizziness. If you think that you have experienced severe health effects, please have everyone leave the room immediately and contact your local poison control center at (1-800-222-1222). 

If the smell is bothersome, but not causing any health effects, then placing the product in a well-ventilated room or garage for several days to a week is your best course of action. After some time, these volatile chemicals should go away. The remaining chemicals, such as polyurethane, should be chemically stable and not a health risk. If the smell persists after a week or so, please contact the retailer or manufacturer and ask for a refund. The release of chemicals from such products after this length of time is not generally normal. 


All chemicals are toxic at some level, yes even water!  All chemicals have safe levels (or virtually safe levels) to which we all can be exposed. Thus, all products contain chemicals that are toxic, but unless the product is releasing chemicals over a safe level, you should not need to worry. The U.S. Consumer Products Safety Commission has a website that can be searched to give information on chemical releases from different products. A list of safe chemical levels can be found here. If you want information on chemicals not found in this list, please feel free to contact me again.



Dr. Michael Dourson


Exposure to Chemicals found in Swimming Pools, Hot Tubs and Spas

September 8, 2021


It’s summertime and families will begin to use swimming pools, hot tubs and spas for exercise and leisure activity.  Health agencies are typically concerned with the water quality due to microorganisms, aka germs.  However, public concerns have been raised regarding potential adverse health effects resulting from exposure to the chemicals that are present in the pool water itself.  When considering exposure to these chemicals, it is important to distinguish between exposure to pool treatment chemicals in their undiluted form and exposure to chemicals present in the pool water itself.  Chemicals used to treat pool water are typically sold in very concentrated forms as they are intended to be added to large volumes of water.  Pool treatment chemicals should be kept in places where children cannot access them as direct exposure can cause breathing problems or may result in burns to eyes and skin. If swallowed, undiluted pool treatment chemicals may be fatal.  Always follow the provided instructions for the safe handling and use of pool treatment chemicals.


From where do chemicals found in swimming pool water come? 
The most common sources of chemicals found in swimming pool water are source water-derived, bather-derived, management-derived, and disinfection by-products:

1)      Source water-derived – Source water-derived chemicals refer to chemical contaminants in the water that was used to fill or re-fill the swimming pool, hot tub or spa.  If the source water was from a municipal drinking-water supply, it may contain organic materials, disinfection by-products, phosphates or other residual chemicals from drinking water treatment processes.

2)      Bather-derived – Bather-derived chemicals refer to the chemical contaminants contributed to the pool water by the swimmers themselves. Such chemicals are predominantly nitrogen-containing compounds found in sweat and urine including urea, ammonia, amino acids and creatinine.  Other chemicals derived from swimmers may include cosmetics, sunscreen lotions and soap residues.

3)      Management-derived – Management-derived chemicals refer to the chemicals directly added by the swimming pool operators to maintain the quality of the pool water.  Management-derived chemicals include, but are not limited to, disinfectants, pH adjusters, coagulants and anti-scaling agents.

4)      Disinfection by-products – Disinfectants added to maintain pool water quality can react with other chemicals found in the pool water to form a variety of disinfection by-products.  Common types of disinfection by-products include, but are not limited to, trihalomethanes (THMS), haloacetic acids (HAAs), chloramines, haloacetonitriles, bromate, chlorite and chlorate.


How does exposure to chemicals present in swimming pool water occur?


There are three main routes of exposure to chemicals in swimming pools, hot tubs and spas:

1)      Direct ingestion – The amount of water ingested by swimmers depends on a variety factors including experience, age, skill and type of activity.  For example, adult competitive swimmers would be expected to have a longer duration of exposure but a lower rate of ingestion due to having greater skill as compared with a non-competitive swimmer.  When evaluating the safety of certain pool chemicals, the U.S. EPA has utilized a default ingestion rate of 50 mL/hour for children (ages 7-10 years) as compared to 12.5 mL/hour for adult competitive swimmers.

2)      Inhalation of vaporized chemicals – Swimmers may inhale pool chemicals that have vaporized from the pool water into the air just above the water’s surface.  Inhalation exposure to pool chemicals is greater in indoor pools where such chemicals may concentrate further in the air due to inadequate ventilation.   Inhalation exposure may also vary based on duration and the intensity of effort exerted while swimming.

3)      Dermal contact/absorption – When swimming, pool chemicals will come into contact with the skin, eyes and mucous membranes of swimmers.  The amount of the pool chemical absorbed into the body by dermal contact also depends of a variety of factors including duration of contact, water temperature and the concentration of the pool chemical in the water. 


Are there adverse health effects associated with exposures to chemicals found in swimming pools, hot tubs and spas?


The most common adverse health effects from exposure to pool chemicals are eye, skin or respiratory irritation.  The irritation is caused by chloramines in pool water and surrounding air.  Chloramines are a form of disinfection by-products produced by the reaction of chlorine with either ammonia or other nitrogen compounds found in the pool water.  Respiratory tract irritation is more common in indoor swimming pools where disinfection by-products may concentrate in the indoor air due to the enclosed space.  Proper maintenance of the pool water chemistry and appropriate ventilation of indoor pool facilities may reduce the occurrence of irritation.  However, some people with preexisting medical conditions may have heightened sensitivity.


Other health effects that have been studied in relation to disinfectant by-product exposure in swimming pools include respiratory changes (such as asthma), adverse reproductive effects and cancer.  However, the current studies on these effects have not been conclusive.  While further research is still needed in order to reach a consensus about the risks of exposure to disinfection by-products found in swimming pools, hot tubs and spas, it is acknowledged by researchers and regulators studying pool chemical safety that health benefits of swimming during childhood and adulthood outweigh the potential health risks of chemical exposure.


How can I reduce my family’s exposure to these chemicals that are present in swimming pool water?


Overall, the risks from exposure to disinfection by-products in reasonably well-managed swimming pools are considered to be small.  Steps that can be taken to reduce the formation of disinfection by-products in pool water can include showering and using toilet facilities, washing off sunscreen lotions, and applying water-tight diapers prior to swimming. It may also be beneficial to increase air circulation in indoor pool settings to reduce the levels of volatile disinfection by-products.

In the end, it is important to maintain microbial disinfection while minimizing potentially harmful disinfection by-products with the goal of maintaining the positive health effects of swimming through exercise while reducing other potential adverse health risks.


Centers for Disease Control and Prevention: Health Swimming/Recreational Water
United States Consumer Product Safety Commission: Safety Education / Safety Guides
World Health Organization – Guidelines for safe recreational water environments


NSF International Toxicology Services Department
Essay also found at http://www.kidschemicalsafety.net/Swim-Chemicals.html.



Lead in Paint & Old Houses – Risks to kids

August 5, 2021


Lead can be found nearly everywhere in the environment, including the air, water, food and soil.  Although lead occurs naturally in the earth’s crust, much of our exposure results from industrial activities, such as manufacturing.  In addition, lead is used (or was previously used) in a wide variety of products, including those found in and around our homes, such as paint, plumbing materials, gasoline, batteries, and cosmetics.  Residential lead-based paint was banned in 1978 by the U.S. Consumer Product Safety Commission.  However, it is estimated that over 80% of the homes built before 1978 contain some lead-based paint.  Lead-based paint used on toys and furniture was similarly banned in 1978.


Exposure to lead can occur through a variety of pathways.  Ingestion of paint flakes and dirt, inhalation and ingestion of dust, and ingestion of contaminated drinking water are common among children as lead tastes sweet.  To reduce your children’s exposure to lead, keep them away from contaminated dirt, remove shoes before entering the house, and remove or cover leaded paint.  Painting the exterior of your home is one of the best ways to prevent exposure to the lead from the existing paint. Additionally, if your home is more than 70 years old, it likely contains some lead plumbing.  Testing your home’s water can show if your water supply contains trace amounts of lead.  Lead in drinking water can be greatly reduced by running the water until it is cold or through use of a pour-through pitcher or other home filter system with a lead reduction rating. Labs verify the lead reduction using methods that must be printed on the product packaging.

In addition to minimizing direct exposure to lead from paint and other sources, the EPA recommends that your children eat at least three meals per day, particularly foods rich in iron and calcium. This type of diet will greatly reduce the amount of lead being absorbed into their bodies. Consumption of fatty and fried foods should also be restricted as these foods are known to increase the absorption of lead in the body.

After it enters the body, lead can cause neurological damage and can delay development in children, if a high enough exposure occurs.  The US Environmental Protection Agency (EPA) reports that children ages 6 and younger are the most vulnerable to lead.  Your pediatrician can administer a simple blood test to determine if your children have been exposed to lead and to estimate their blood levels of lead.  The reference level at which U.S. Centers for Disease Control recommend public health actions be considered is 5 micrograms per deciliter of blood (µg/dL). The Ohio Department of Health runs the Ohio Healthy Homes and Lead Poisoning Program, which has published a helpful brochure that includes a list of criteria that you and your family can review together to determine whether this testing might be necessary for your children. If you do get your children tested and find that they have been exposed, several treatment options are available, which are described in the brochure.

Under the Renovation, Repair and Painting Rule administered by the EPA, federal law requires that anyone hired to renovate, repair, or do paint preparation on a house built before 1978 (that a child under 6 visits regularly) be certified and follow specific work practices to prevent lead contamination.  Outdoor paint renovation should include ground covers.  Any sanding equipment requires a shroud and HEPA vacuum attachment.  More information on your rights as a tenant and how to keep your family safe during this type of renovation can be found. Additionally, you can also verify that a contractor is certified by checking EPA or by calling the National Lead Information Center at 1-800-424-LEAD (5323) or ask to see a copy of the contractor’s firm certification.


A more complete essay on this topic can be found at: http://www.kidschemicalsafety.net/Lead-Paint-and-Old-Houses.htm.  A video that brings home some of these issues can be found at: https://www.youtube.com/watch?time_continue=5&v=IYpPOpAq8Vs&feature=emb_logo.



July 5, 2021

A true story of chemical risk and benefits:Rats, Cats And Parachutes

Calvin Willhite, Ph.D.
California Environmental Protection Agency (retired)

Michael L. Dourson, PhD., DABT, FATS, FSRA
Toxicology Excellence for Risk Assessment (TERA)


Our story is about a pesticide. People are often worried about pesticides because they are toxic chemicals. Pesticides are toxic so that they can kill things - like bugs. DDT is a bug spray. DDT was outlawed in many countries because once you spray it, DDT breaks down only very slowly in the environment. Since it stays around for a long time, it moves up the food chain and when birds eat bugs sprayed with DDT the chemical causes their egg shells to become thin. The egg shells become so thin that the mothers break the eggs when they sit on them, and the baby birds die. In fact, DDT almost wiped out falcons, hawks, condors and pelicans. After DDT was outlawed, the numbers of birds increased. So at first glance, banning DDT seems like a smart move.

Malaria is a disease with high fever, shaking, chills, vomiting and sweating that you can get from a mosquito bite. Did you know that there are 300,000,000 to 500,000,000 cases of malaria every year? And that nearly 3,000,000 people die every year from malaria? Did you know that most of those who die are children less than 5 years old? Mosquitoes are responsible for infecting people with malaria and people with malaria die when the malaria parasite gets into their liver and brain. If you want to stop malaria you need to kill the mosquitoes that carry the parasite. The chemical DDT is great if you want to kill mosquitoes since it is toxic to them and usually it does not hurt people.

The places with the most malaria are places with lots of mosquitoes. Borneo (an island we now call Indonesia) is a place with lots and lots of mosquitoes and lots and lots of malaria. Between 1952 and 1955, the World Health Organization began spraying DDT in Borneo to kill mosquitoes to control malaria. The chemical was sprayed on house walls and under beds so it would kill the mosquitoes before the mosquitoes could bite the people who lived there. Sure enough, the DDT killed lots of mosquitoes and since there were fewer mosquitoes, only a few people got malaria. But cockroaches aren't bothered much by DDT and the local caterpillars learned to avoid the DDT. As it turns out, jungle wasps that normally laid their eggs in the caterpillars died from DDT. The cockroaches were fine and without the wasps, the numbers of caterpillars increased and increased. Then the caterpillars started eating the thatched roofs of the houses. At the same time, the cockroaches and caterpillars that had been sprayed with DDT were eaten by geckoes (yes that same long-tailed lizard that appears in the car insurance commercials on TV). This is because geckoes like to dine on caterpillars along with a side of cockroach.

Because DDT accumulates up the food chain, the geckoes who ate the wasps, roaches and caterpillars that had DDT in their bodies also accumulated lots of DDT. The geckoes got sick. The sick geckoes slowed down. The island cats walked all around inside the houses and they usually entertained themselves by hunting and eating geckoes. As the cats walked through the houses the cats got DDT on their paws then they licked their paws and in so doing, they ate some DDT. When the geckoes became slow, the cats were very pleased and they ate as many geckoes as they could. Without enough geckoes and now that the wasps were gone, there were more and more caterpillars and they began to eat more and more of the thatch that was used to make the roofs on the houses. Then the roofs of the houses fell in.

But things only got worse.

The cats eating the geckoes only lasted for a little while, because the cats were poisoned by the DDT that was on their paws and inside the geckoe bodies.  The cats died.  When the cats were gone, the rats on Borneo declared a holiday and they had lots and lots of rat babies.  When all those rat babies grew up, this increased the numbers of fleas that lived on the rats.  Those nasty fleas can carry deadly bubonic plague (The Black Death) and plague can be transmitted from the fleas to the people who lived in the houses with the broken roofs.

So, now what?

What to do about all these rats with fleas and this new risk of plague? Well, the villagers decided they needed more cats to get rid of the rats and they decided to ask for help. They went to see the British Royal Air Force. So together with the people who lived in the houses with the broken roofs, the Royal Air Force helped the village to find some cats from the British Commonwealth of Malaysia and the Air Force parachuted cat reinforcements onto the island and the fresh cats took up the work of killing the rats..

But all of these efforts did not get rid of all of the mosquitoes or the malaria. Today the World Health Organization is still responsible for stopping malaria and the World Health Organization is stuck with a choice. Should we keep using DDT to kill mosquitoes? Or should we stop using DDT? On the one hand we have the real risk of death from malaria. On the other hand we have the toxicity of DDT to birds, to fish and to other animals. To make matters even more difficult scientists found out that when DDT was fed to laboratory mice it caused liver cancer and some studies suggested DDT might do the same thing in people. To decide what to do with DDT, the World Health Organization needed to know how dangerous DDT might or might not be: which is worse, to spray DDT to kill mosquitoes and take a chance with cancer or not to spray and let the mosquitoes do as they please? The World Health Organization tried other bug sprays, but these were even more toxic and they were more expensive than DDT (remember we are talking about many countries and many millions of people at real risk of death from malaria).


To help the World Health Organization make a decision about DDT, they looked at all the laboratory studies on DDT and then they used a computer to calculate the projected risk of cancer in people who lived in the houses that were sprayed with DDT. This projected risk is not the same as the real risk since this is an estimate based on what scientists measured in mice. Using their best estimate, the World Health Organization found that not more than 3 in 100,000 people would be at risk for cancer after spraying DDT.

How would you decide this question? How would you balance the health risks of DDT against its benefit to reduce malaria? What did the World Health Organization do? To this very day, the World Health Organization sponsors DDT spray inside homes in places like the jungles of Indonesia where malaria is common. This is because of the high numbers of people who die every year from malaria compared to the estimated (theoretical) numbers of people who might get cancer. So you can see the concept of "safety" is relative.


Fact Check and Resources  
Harrison, T. 1959. World Within: A Borneo Story.  London: Cresset Press.
O’Shaughnessy, P.T. 2008. Parachuting cats and crushed eggs. The controversy over the use of DDT.  American Journal of Public Health 98(11): 1940-1948.  

Royal Air Force. 1960. Operations Record Book. Flight of 48th Squadron. March 13. Changi, Singapore.  Compiled by Fg.Off.Humphrey

World Health Organization. 2006.  WHO gives indoor use of DDT a clean bill of health for controlling malaria. 
http:// www.who.int/mediacentre/news/releases/2006/pr50/en/

World Health Organization. 2011. Strengthening malaria control while reducing reliance on DDT.  http://www.who.int/ipcs/capacity_building/ddt_statement/en/index.html

World Health Organization. 2011. DDT in indoor residual spraying: human health aspects.  Environmental Health Criteria 241. 391 pp. Geneva: WHO



Calvin Willhite, Ph.D.
California Environmental Protection Agency (retired)

Michael L. Dourson, PhD., DABT, FATS, FSRA
Toxicology Excellence for Risk Assessment (TERA)

If you think parachuting cats is a fairy tale, the official Operations Record Book from March 13, 1960 taken down by the crew of a British Royal Air Force (RAF) Beverly transport plane from Singapore describes that it “carried out a unique drop to Bario in the Kelabit Highlands in Sarawak that included over 20 cats to wage war on rats”.  The Dayak people of that village thanked the RAF and thanked “all of the cat donors and cat basket makers” and added that “all of the cats are safe.”



June 4, 2021

Hey toxicologists, is organic food safer to eat?

By Michael L. Dourson, PhD., DABT, FATS, FSRA

Pick just about any newspaper or journal and during the course of a year, one or more articles will be devoted to the benefits (or not) of organic foods and the downsides (or not) of conventionally grown food with pesticides and herbicides. These articles are often confusing. 


So how does one sort them out?


Food, whether organically or conventionally grown, is a combination of chemicals, many of which our bodies need in order to function well. Organic food comes from plants grown without added antibiotics or growth hormones, pesticides, herbicides or genetic modification , whereas conventionally grown food may use one or more of these products.


However, not all chemicals in food are useful to our body, and some of them are harmful at a certain level, like too much aflatoxin---a natural fungal product---in peanut butter. And did you know the plants we grow for food naturally produce pesticides and herbicides to protect themselves from insects and weeds? Any gardener who has tried to grow tomatoes near a walnut tree can tell you this is true---the walnut tree’s roots produce a herbicide that is poisonous to tomato plants. The use of pesticides and herbicides, whether human-made or natural, often results in small levels of these chemicals in our food.


Genetic modification (GM) of a food crop, whether done in the lab or through traditional crossbreeding, is often one way to get the crop to develop a new pesticide or herbicide, or to increase the level of an already existing natural one. Such modification may also give the crop a way to resist damage by a human-made herbicide. So corn can be genetically modified in the lab to make a protein to protect it against insect damage and at the same time to resist damage by human-made herbicides used to kill weeds. The use of GM corn with both of these traits is popular because it not only increases yields, but also reduces plowing, soil erosion, and use of conventional pesticides and herbicides. Of course, corn has been genetically modified through traditional crossbreeding for years to increase yields and resist pests.


So now to the question!  Is organic food safer to eat?  Or perhaps, are the small levels of pesticides, herbicides and genetic modifications in our food, whether human-made or natural, harmful? 


Many organizations work on a daily basis to answer this latter question. In fact, tens of millions of dollars are spent by competing industries on appropriate experimental animal and exposure studies. These studies then are reviewed by toxicologists to establish safe levels. These levels are then compared with the anticipated exposures when the pesticide, herbicide or genetic modification is used according to its label. If the anticipated exposures are below the safe levels, then the uses are permitted and the small levels of these chemicals in our food are not harmful. Although such testing is generally not done on naturally occurring plant chemicals, human experience would suggest that exposures to many of these naturally occurring pesticides, herbicides or genetic modifications are also below safe levels, and thus, are also not harmful.


When comparing organic versus conventional methods of growing food, other issues may be important. For example, organically grown foods may better maintain a sustainable farm practice, may reduce unanticipated environmental impacts of a human-made pesticides, herbicides or genetically modified plants, and would reduce accidental and often demonstrated harm to workers from over exposure to these chemicals. However, organic farming generally needs extra plowing so soil erosion is increased when compared with conventional farming. And while eating organic foods has been demonstrated to lower consumer exposure to some human-made pesticides and herbicides, insect damage from unprotected plants can cause natural pesticides and herbicides to increase. Additionally, there is no strong evidence that organic foods are significantly more nutritious than conventional foods.


A Google query entitled “organic and conventionally grown foods, including GM foods” will yield many websites, many of which were judged by the scientific staff of Toxicology Excellence for Risk Assessment (TERA) as too biased, not credible, or non-related. However, some sources appear to of unbiased, credible and related. For example, nutritional content of food grown by either method does not appear to differ. Other sources can be accessed to answer numerous other questions.


Forman J. and J. Silverstein.  2012.  Organic Foods: health and environmental advantages and disadvantages.  Pediatrics: 2012-2579.  October 22.

Jason J. Hlywka , Gerald R. Stephenson , Mark K. Sears , Rickey Y. Yada.  1994. 
Effects of insect damage on glycoalkaloid content in potatoes (Solanum tuberosum).  J. Agric. Food Chem., 42 (11), pp 2545–2550.



May 4, 2021

Too much of a good thing?

By Michael L. Dourson, PhD., DABT, FATS, FSRA


We have all likely heard someone say something is “too much of a good thing.” This applies to foods, like ice cream, drinks, like wine, and many kinds of activities, like watching movies.  However, this also applies to chemicals to which we are exposed every day, or about which we often read in our daily news. 

In fact, all chemicals are toxic at some level – some can cause harm at very small concentrations, while others need a large amount before there is a danger to our health. For example, ingesting large amounts of dihydrogen monoxide can cause low blood sodium concentrations leading to nausea, fatigue, confusion and seizures, and even death, but few people would want to ban di-hydrogen (H2) mono-oxide (O)---also known as “water”--- from public sale and or other uses, since water is safe and necessary when we drink a normal amount.

For many chemicals, however, it’s difficult to know what level causes or does not cause harm. For example, most people know arsenic as a poison, but may not know that many foods contain small amounts of arsenic, since it is a part of our environment.  How much arsenic can people eat and not be harmed? 


You might remember the scare a while back about too much arsenic in apple juice.  The U.S. Food and Drug Administration analyzed a large number of apple juice samples for arsenic and compared them with their estimate of its safe dose, the level at which no harm was expected.  The FDA concluded that the very low levels of naturally occurring arsenic in apply juice were not a public health risk and the juice was safe for consumption.  Eventually FDA developed guidance for manufacturers.

Because of this difficulty, toxicologists have been trained to make a determination of levels where a chemical causes harm and where it does not, generally in experimental animals.  These determinations are then evaluated by scientists who specialize in risk assessment to make a judgment about the safe dose or safe level of the chemical to humans.   These risk scientists work in governments, industries, consultancies, and, to a less extent, universities and non-governmental organizations (NGOs).


These safe levels go by different names, a common one in the US is the reference dose (RfD).  But despite different names and slightly different approaches, risk scientists all follow three basic steps:

  1. Toxicity data are reviewed from laboratory studies generally on animals to confirm the levels of exposure that show harm and those which do not.  Sometimes important information is found from unintended human exposures.
  2. Uncertainties in the data and analyses are then considered, particularly when using animal studies, and a judgment is made of a chemical exposure that would be safe, even for sensitive groups of people (like children or the elderly).
  3. New research may be requested of toxicologists to resolve uncertainties or unclear data or analysis.


If you want to learn more about safe levels of chemicals, or how they are developed, many agencies provide a wealth of information.  For example:

  • U.S. National Library of Medicine, has useful toxicity information about chemicals on its websites (see http://toxnet.nlm.nih.gov);
  • U.S. Environmental Protection Agency also has a wealth of information on many of its websites (http://epa.gov; 
  • Society of Toxicology has its annual meeting in March (see https://www.toxicology.org/index.asp).
  • Toxicology Excellence for Risk Assessment assesses the risk to chemicals and shares this information (see http://www.tera.org); 
  • Toxicology Education Foundation has produced an excellent 15-minute video called "Is It Safe?" (http://toxedfoundation.org/is-it-safe-video-english-with-japanese-subtitles/) that provides information for the general public about chemicals and risk so that you can make good decisions associated with everyday products (see also other topics at: http://toxedfoundation.org).
  • American Council on Science and Health at https://www.acsh.org has essays on numerous topics many of them associated with chemicals and their safety.


These are only six examples of many groups that work on behalf of the public to keep us safe.



April, 2021

Who is a toxicologist and how is s/he different than my medical doctor?

Michael Dourson, PhD, DABT, FATS, FSRA 
Bernard Gadagbui, MS, PhD, DABT, ERT

Toxicology, the study of poisons, is often thought of as a new discipline. It’s not. It has been around as long as people have been trying out different types of food, and using the occasional poisonous plant, or animal, to dispatch a rival. Toxicology today is more disciplined, with scientists and medical doctors studying various ways the plethora of chemicals to which we are daily exposed to can either be of use, not of use, or downright dangerous. However, even sometimes very dangerous chemicals can otherwise be useful (think botox here, https://www.youtube.com/watch?time_continue=7&v=fFvYUdljVK0&feature=emb_logo). If you want to get a sense of toxicology that is readily understandable, here are 3 sets of facts that can be used around the proverbial office water cooler, or at your next party, should the conversation need a new direction:


  • Life is chemistry. We are exposed to tens of thousands of chemicals every day.  A cup of coffee has about a 1000 chemicals. Most garden vegetables have just as many, including many natural pesticides like solanine found in potatoes at high concentrations in all green parts (but even in the potato we eat at a safe level).  We could go on and on and…
  • All chemicals are toxic at some level. Yes, even water. Drink too much and it will kill you. Drink a little bit less and it will disrupt your endocrine system, specifically the hormones associated with your kidneys and adrenal glands.
  • All chemicals have a safe dose if they do not cause cancer or virtually safe dose if they cause cancer. Yes, they do!  It is the dose that makes any chemical a poison.  Even a very toxic chemical like arsenic, which has dispatched more than one famous person (Napoleon perhaps?), has a level below which folks do not worry about. Good thing too since arsenic is a naturally occurring element that can be found in nearly all water and food we eat daily if one looks closely enough.


So, what do toxicologists do every day?  Well, like many occupations, toxicology has a number of sub-disciplines.  The one we deal with on a daily basis is human health risk assessment and the related area of regulations.  This area is likely to be one in which you are most familiar, since fear of chemicals is prevalent in today’s social media and chemicals are often written up in mainstream news outlets in negative terms.  Most of these stories are short on the science and long on the scare, so beware and check the backgrounds of the author and those s/he quotes before you start believing anything.


Toxicologists adept at risk assessment and regulation can be found in government, industry, consulting and, to a much lesser extent, academic and NGO organizations.  Sections of scientific organizations are even devoted to risk assessment and regulation.  On a daily basis, these toxicologists review studies done on particular chemicals and mixtures to determine safe levels of exposure.


Other areas of toxicology will likely not surprise you.  Some toxicologists conduct chemical experiments on animals or cell cultures to determine the level at which effects occur.  Some study the structure of a chemical and compare it to chemicals that have similar structures for insights.  Some extract natural chemicals from plants and animals looking to make new drugs or other useful chemicals.  And all of this and other related work necessitate advanced training in biology, chemistry, physiology and pathology and other disciplines, often ending up with conferral of a masters or doctorate in toxicology.


So, where does your medical doctor fit in?  Well, some of the most famous toxicologists are also medical doctors, and so the degree, either an MD or PhD is really not as important in determining whether someone is a toxicologist as the underlying work (https://en.wikipedia.org/wiki/John_Doull_(toxicologist).  However, a useful distinction is that a medical doctor is often focused on your health and will get you into a hospital if this is needed.  A doctor of toxicology is concerned with preventing ill health from chemical exposure---we try to keep you out of the hospital.  Another useful way to look at toxicology is that it is preventive medicine.  We are trying to lessen the workload of our medical doctor colleagues by finding ways for you to avoid disease.


So, next time you read a social media post or newspaper article and have a question, send us a note, ask another toxicologist for some help, or go to one of these websites to check out relevant information:


Email dourson@tera.org; gadagbui@tera.org
Phone 513.542.7475 Ext: 105; 513.542.7475 Ext: 104
Mobile Phone 513.543.2892; 513.313.3160 

Questions to consider are: How many of the sources are from scientists?  How many of these scientists are toxicologists?  How many of these toxicologists, if any, are board-certified? 

The Society of Toxicology’s specialty sections for Regulatory and Safety Evaluation and Risk Assessment are two prime examples.