Comparing Pollutant Levels Between Different Diets

Image Credit: Mitchell Haindfield / Flickr. This image has been modified.

Comparing Pollutant Levels Between Different Diets

The results of the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) study were published recently. This study of a California birth cohort investigated the relationship between exposure to flame retardant chemical pollutants in pregnancy and childhood, and subsequent neurobehavioral development. Why California? Because California children’s exposures to these endocrine disruptors and neurotoxins are among the highest in the world.

What did they find? The researchers concluded that both prenatal and childhood exposures to these chemicals “were associated with poorer attention, fine motor coordination, and cognition” (particularly verbal comprehension) by the time the children reached school age. “This study, the largest to date, contributes to growing evidence suggesting that PBDEs [polybrominated diphenyl ethers, flame retardant chemicals] have adverse impacts on child neurobehavioral development.” The effects may extend into adolescence, again affecting motor function as well as thyroid gland function. The effect on our thyroid glands may even extend into adulthood.

These chemicals get into moms, then into the amniotic fluid, and then into the breast milk. The more that’s in the milk, the worse the infants’ mental development may be. Breast milk is still best, but how did these women get exposed in the first place?

The question has been: Are we exposed mostly from diet or dust? Researchers in Boston collected breast milk samples from 46 first-time moms, vacuumed up samples of dust from their homes, and questioned them about their diets. The researchers found that both were likely to blame. Diet-wise, a number of animal products were implicated. This is consistent with what’s been found worldwide. For example, in Europe, these flame retardant chemical pollutants are found mostly in meat, including fish, and other animal products. It’s similar to what we see with dioxins—they are mostly found in fish and other fatty foods, with a plant-based diet offering the lowest exposure.

If that’s the case, do vegetarians have lower levels of flame retardant chemical pollutants circulating in their bloodstreams? Yes. Vegetarians may have about 25% lower levels. Poultry appears to be the largest contributor of PBDEs. USDA researchers compared the levels in different meats, and the highest levels of these pollutants were found in chicken and turkey, with less in pork and even less in beef. California poultry had the highest, consistent with strict furniture flammability codes. But it’s not like chickens are pecking at the sofa. Chickens and turkeys may be exposed indirectly through the application of sewer sludge to fields where feed crops are raised, contamination of water supplies, the use of flame-retarded materials in poultry housing, or the inadvertent incorporation of fire-retardant material into the birds’ bedding or feed ingredients.

Fish have been shown to have the highest levels overall, but Americans don’t eat a lot of fish; so, they don’t contribute as much to the total body burden in the United States. Researchers have compared the level of PBDEs found in meat-eaters and vegetarians. The amount found in the bloodstream of vegetarians is noticeably lower, as you can see in my video Flame Retardant Pollutants and Child Development. Just to give you a sense of the contribution of chicken, higher than average poultry eaters have higher levels than omnivores as a whole, and lower than average poultry eaters have levels lower than omnivores.

What are the PBDE levels in vegans? We know the intake of many other classes of pollutants is almost exclusively from the ingestion of animal fats in the diet. What if we take them all out of the diet? It works for dioxins. Vegan dioxin levels appear markedly lower than the general population. What about for the flame retardant chemicals? Vegans have levels lower than vegetarians, with those who’ve been vegan around 20 years having even lower concentrations. This tendency for chemical levels to decline the longer one eats plant-based suggests that food of animal origin contributes substantially. But note that levels never get down to zero; so, diet is not the only source.

The USDA researchers note that there are currently no regulatory limits on the amount of flame retardant chemical contamination in U.S. foods, “but reducing the levels of unnecessary, persistent, toxic compounds in our diet is certainly desirable.”

I’ve previously talked about this class of chemicals in Food Sources of Flame Retardant Chemicals. The same foods seem to accumulate a variety of pollutants:

Many of these chemicals have hormone- or endocrine-disrupting effects. See, for example:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

31 responses to “Comparing Pollutant Levels Between Different Diets

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  1. Dr. Greger, I look forward to your daily posts and videos. You have definitely had an influence on my food choices. The studies that you cite regularly add a degree of justification in my mind to direct and support my decision to continue with the plant based diet that I have chosen for the past 3 years.

        1. I wouldn’t be so sure as to mark any fish as “clean”. Wild-caught fish are exposed to contaminants because we actively dump waste into oceans and rivers.

        2. @Jerry Please don’t spread misinformation like that.

          @Von Wild caught fish and farm raised fish both have their share of pollutants and contaminants. Feel free to search the topic on nutritionfacts

          1. Farm raised fish are not in the same league as wild Alaskan caught fish in terms of pollutants. If you’re going to tell people not to spread misinformation, please don’t do it yourself, either.
            John S

  2. which vegan foods are highest in the pollutants? Would it be the fatty nuts and seeds, and
    avocados, as compared to green veggies, roots, potatoes, fruit? Most of us here avoid animal
    products, so this would be relevant for the masses that looked to be mindful of this.

    Also, out of curiosity, did these studies analyze exclusively organic animal products?
    Were the studies used to make these claims based on a mix of farmed raised and ocean
    caught, or one or the other? It makes a huge difference, from what I have studied.

    How about fat-free dairy? Most the dioxins and PCBs are in the fats, right? This stuff seems
    relevant for all people to know on earth, in order to make informed decisions, otherwise we (here)
    and elsewhere are just guessing how accurate these studies are. I’d love to tell my organic meat
    eating friends, organic fat-free dairy eating friends, and wild caught fish eating friends to make changes, but it is not fair to do so without knowing if studies have
    answered these questions. Thanks.

    1. I see your point and I think it’s fair to want to answer those questions. On the other hand, those are surface level questions. Neurobehavioral developmental problems in children are certainly serious issues, but have you spoken with your friends about organic grass fed beef, cage free chicken, and organic Wild caught salmon as still being beef, chicken, and salmon? No matter how much you clean up the product (maybe animal food products really are less contaminated with PBDEs), you still can’t change the basic package. By eating beef, chicken, and salmon you are bringing saturated fat and cholesterol into your body, both risk factors for heart disease, diabetes, erectile dysfunction, and many other common diseases our nation suffers from. I know this is old news, but it’s important. Do your friends not care about this result?

    1. Don’t worry about goat milk because goat eats grass and not junk fed by human. And goat roams and is not raised in cages. Goat is the best clean food.

      1. Thank you Jerry for responding to my query about goat milk safety. I have stage 4 COPD and have recently decided to adapt a vegan diet. However, if goat milk/yogurt are devoid of the cow milk pollutants, I’m inclined to continue consuming them.

        1. It is very humane to drink goat milk as goat is not raised in cage. Free roaming and grass fed goat and cow milk has CLA enzyme which is protective to heart health and other health.

    2. William,

      One (non-human) species’ milk is not healthier than another.
      They still contain saturated fat, cholesterol, and because it’s higher up the food chain, more contaminants than plants.

      The only milk suitable for humans is human milk (for infants, then).

      Jerry Lewis is spreading misinformation

      It contains even more saturated fat per serving than cow’s milk and doesn’t contain enough of the CLA enzyme to experience significant results.

  3. Has there been a study or research comparing these, presumably, US results with other countries and geographical regions?

    I would have thought, and hope that this is more than wishful thinking, that agricultural, industrial and regulatory practices in other ( than US) parts of the world would not be dominated by the insatiable profit motive that blinds folk to longer term consequences of practices, that are detrimental to human health and especially children’s development.

    I am a relatively recent vegan ‘convert’ as a consequence of your very informative content, book and videos.
    Appreciatively yours
    John Loty

  4. The land disposal of sewage sludge has resulted in significant controversy, and a resistance movement is rightfully building to this misguided policy. Quite simply, the science doesn’t support the disposal of sewage sludge across the landscape. The supposed benefits are more than offset by the risks toward human and environmental health.
    As scientists, we have been watching the issue with increasing concern.
    An unimaginably large number of chemical and biological contaminants exist in these materials, and they persist in the product up to, and after, land disposal. Scientific investigations have identified only a tiny fraction of the total contaminant load. We cannot even say with any degree of confidence what the true range of contaminant risk is from the sludge. Call it an “unknown unknown.” Because of potential synergistic interactions between the contaminants in the sludge, the risks are largely unknowable.

    Most public discussions of the chemical contaminants in sewage sludge involve well known groups such as heavy metals, flame retardants, and pharmaceuticals, among many others. But these are just the contaminants we have identified. To refer to our current knowledge base as the tip of the iceberg would be grossly overestimating how much we actually do know.

    Regulators and others — including elected officials — up and down the policy chain appear to lack a real appreciation for the scope of the problem, and the costs of beginning to understand it. If a city were to test the sludge just once for all possible contaminants in the material, the bill would be well into the hundreds of thousands of dollars.

    You are not going to find a problem if you don’t look for it. Of course, over time, that problem may also come looking for you.
    To illustrate the difficulties, take just one group of persistent, bioaccumulative, and toxic compounds known to be in sewage sludge at high concentrations: brominated flame retardants. Perhaps the most well known sub-class of the brominated flame retardants are called polybrominated diphenyl ethers (PBDEs). There are 209 different PBDEs, each of which has a unique toxicology and environmental fate. PBDEs have been studied around the world for several decades, and despite many millions of dollars in research and thousands of dedicated researchers, we still have a very poor understanding of the true risks from their release into the environment.

    This is just one contaminant class among many. There are also 209 different members of the PCBs. Similarly, add in another 210 chlorinated dioxin “congeners.” And on the total number of contaminants in sewage sludge climbs as we begin to consider that effectively all current and legacy industrial chemicals end up in our sewage, and during the treatment process they move into the sludge. If you apply the sludge to the land, we have transferred our toxic effluent onto the landscape.

    Now consider that while the tens of thousands of these commercial chemicals are a possible problem which we barely understand, the risks from the much larger suite (i.e., millions) of possible degradation products are essentially unknown. Then add on all pharmaceuticals and personal care products, as well as any other compound we use in the home or at work, and all their potential degradation products.

    We are often asked by regulators, politicians, and the general public what to do about the issue. Give us the tests and we will do them, they claim. In response, we say that not only can you not afford to do all the required tests on your own (the costs must be distributed across entire countries and the international community as best we can, and even that is almost unaffordable), but many of the required tests require advances in technology which we do not yet possess.

    The complexity discussed so far just touches on the chemical contaminants. Add to that the massive numbers of biological contaminants — bacteria, viruses, prions, etc. — and what we see are the decision makers throwing their hands up in frustration. As they should. The current and future problem is inconceivably large, particularly since the human population is producing sewage sludge at a rapidly growing rate.

    Those from the large public and private sector industry that has developed around marketing and selling sewage sludge for land disposal — which we collectively term Big Sludge — claim the materials are “non-toxic” and a resource to be cherished, not shunned. The state of the science does not agree with this oversimplification.

    While there have been some attempts to review the science surrounding sewage sludge, these are generally wanting. Either the reviews are out-of-date and incomplete, failing to account for all that we do know about emerging contaminants and what we don’t know about all contaminants, or they are written more as promotional materials for Big Sludge in an attempt to sell the product to an ever more sceptical public.

    What should we do in response to all these concerns? Immediately halt the land disposal of sewage sludge as a starting point, and begin either stockpiling or landfilling the material in secure locations with full leachate collection systems until a more responsible means of dealing with the problem is implemented. In the meantime, the science must continue in an effort to better understand the risks and to develop more effective treatment technologies.

    We also see municipalities and regional districts talking about the revenue stream from selling their sludge for land disposal, but are they telling the taxpayers they are supposed to represent about the very large potential risks from the knowing and wilful contamination of lands, waters, and the atmosphere that arises from these choices? Increased health care costs, decreased property values, and toxic tort lawsuits have collective liabilities to Big Sludge over time that far outweigh the relatively small cash flows currently coming in to the public purse.

    Governments are playing Russian roulette with sewage sludge, and over time there is a high probability this game will be lost at the public’s expense.

    Sierra Rayne, PhD
    John Werring, MSc, RPBio
    Richard Honour, PhD
    Steven R. Vincent, PhD

    Sierra Rayne is an independent scientist; John Werring is a senior science and policy advisor for the David Suzuki Foundation; Richard Honour is the executive director for The Precautionary Group; Steven R. Vincent is the Louise Brown Professor of Neuroscience with the Department of Psychiatry at the University of British Columbia.

    1. Thank you, Vincent Lucas, for guiding us to look at some basic issues in agricultural production. I would assume, the issue is of equal concern to vegetarians and nonvegetarians alike, even though USDA organic certification forbids the use of sludge for three years prior to granting certification. I hope that the relevant group of scientists will gain influence with regard to sludge disposal to stop the contamination of our lands.

    2. A lot of Indian vegetarian food includes ghee (clarified butter) and vegetable oil, components that advocates of whole plant based vegan diets avoid (butter and vegetable oils cause unhealthy effects on endothelial lining of arteries).

  5. I try to eat as close to a whole food plant based diet as possible, but you said the exposure of PBDEs came from dust as well as diet. Is there a way we can further restrict our exposure by keeping our houses cleaner, or by not using certain cleaning supplies? If it’s just dust, does that mean if I kept a spotless living space I could get my levels very close to zero?

    1. Aliena,

      You’re on the right track…… the main exposure is your bed, household foam products……. see this article for more info: /tip-4-avoid-fire-retardants. You will not be able to bring your levels to zero regardless of how hard you try. Oh and let’s not forget that although the family of PBDE’s have been replace by other toxic fireproofing agents….they are equally toxic….

      Consider your home….. from carpet padding, to the couch and the list goes on to your computer….. and you get the idea. What you can successfully do is follow some clear indications such as purchasing furniture that has the TB117 label (the one telling you not to remove or else) that says it does not use fireproofing products, since 1/2015. And does your vacuum have a HEPA filter (the highest rated and not a bypass system) Yep a bit complex eh…..see which will be posting vacuums, beds, air cleaners, etc. to address this issue shortly.

      And of course the food choices make a difference. WFPB is going to help.

      You can make a MAJOR change and decrease the overall level… don’t be discouraged its a process that will take some time and thought.

      Good luck and remember lightening the load of toxins is a worthwhile endeavor regardless of how much you reduce your exposures. This is because the cumulative load is one of the real keys.

      Dr. Alan Kadish moderator for Dr. Greger

  6. Dr Greger writes here that “American don’t eat a lot of fish”… yet an article just published starts with “Americans eat a lot of fish”. (It continues with: “In 2015, annual consumption rose from 14.6 to 15.5 pounds per person, the largest jump in decades—one that put the U.S. second in the world in terms of seafood consumption, right behind China and before Japan. The demand appears to driven, at least in part, by seafood’s wholesome image: U.S. dietary guidelines recommend 8 to 10 ounces a week, and nutritionists increasingly point out the nutritional importance of the omega-3 fatty acids that fish offer in abundance. At the same time, some Americans are eating less meat out of concerns about animal welfare, and fish—which lack the developed neocortexes of cows, pigs, and chickens—may feel like a more enlightened, humane choice.”).

  7. Can anyone help with a nutritionist in London uk who supports vegan eating for pregnancy? The nutritionist I went to does not recommend plant food for pregnancy as she says if you stress your body is unable to sufficiently convert this(plants / beans) to protein. She also says your body will become eventually allergic to meat, if you don’t eat it for too long; and then you may need it later on in life after following a vegan diet as you may be lacking in minerals. Very confusing to know what is best to do. Thanks!

    1. | MichdG commented on Comparing Pollutant Levels Between Different DietsSorry I don’t know a nutritionist in London (but I’m right now at a festival which the organisers of the Vevolution events, based in London, are also attending, so I’ll ask them. You could also ask the team who run – e.g. Klaus Mitchell – as they’re also based in London and have many contacts. To reassure you though, this is the current statement (and has been for a number of years I believe) of the largest association of professional nutritionists in the World: “It is the position of the Academy of Nutrition and Dietetics that appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. They are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes. Plant-based diets are more environmentally sustainable than diets rich in animal products because they use fewer natural resources and are associated with much less environmental damage. Vegetarians and vegans are at reduced risk of certain health conditions, including ischemic heart disease, type 2 diabetes, hypertension, stroke, certain types of cancer and obesity. Low intake of saturated fat and high intakes of vegetables, fruits, whole grains, legumes, soy products, nuts, and seeds (all rich in fiber and phytochemicals) are characteristics of vegetarian and vegan diets that produce lower total and low-density lipoprotein cholesterol levels and better serum glucose control. These factors contribute to the reduction of chronic disease.” (Melina V, Craig W, Levin S (2016). Position of the Academy of Nutrition and Dietetics: vegetarian diets. J Acad Nutr Diet. )

    2. Here is the link to the position paper of the Academy of Nutrition and Dietetic Association which is the professional organization for nutritionists. It clearly states a vegan diet is healthy during any part of the life cycle including pregnancy. There are Facebook sites for vegan childrearing; check out those for help.

  8. Hello,
    Is there any research into whether or not grass fed or pasture raised meat contains less PBDEs than industrial farmed meat? Thank you!

    1. Logically, grass fed or grain fed animal meat does not have more pollutants than your kale or broccoli. It’s because even grain fed cow eats the same grain that humans eat. But the contamination happens during processing and meat tends to have more contamination than plants depending on how clean is the processing plant.

      But the main and important difference between grass fed and grain fed cow meat is in the nutrients. Grass fed animal meat contains far more nutrients than their grain fed counterpart.

      So you choose grass fed cow meat from a reputable food store.

      1. Jerry Lewis: Your logic is wrong. You are missing the concept of bioaccumulation (sp?), which means that your animal meat (whether grass fed or not) absolutely does have more pollutants than plants. Bioaccumulation is a very basic, well understood and completely uncontested biological phenomenon.

    1. Hi Gwyn, sorry for the belated reply, but it’s my understanding that flax meal and ground flax are essentially the same.

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