Backyard Talk

Low Doses Matter

You were right.

How often have you been told that the levels of a particular chemical found in the air, soil or water are very low and thus not significant, or that the risks are so low that there is no cause for alarm?  This is what EPA said about dioxin just about a month ago when they released its non-cancer report.   Now a new scientific report is helping make the case that most people living in a contaminated community have known for years – low dose effects matter.   A group of scientists led by Laura Vandenberg at Tufts University reviewed literally hundreds of published scientific papers, many on endocrine disruptors, and found dozens of examples of low dose effects.  These papers included a wide range of chemicals including many found in the environment, our food, and many consumer products such as plastics, pesticides, and cosmetics.  The researchers found “overwhelming evidence that these hormones altering chemicals have effects at low doses and that these effects are often completely different than effects at high levels.”  Low doses are defined as levels occurring in the range of typical human exposure.

This is a remarkable paper.  It says and supports what community leaders having been saying for years –  low dose exposures are damaging people’s health and the way scientists evaluate health risks using risk assessment no longer works.  One of the key conclusions in this paper is that “the effects of low doses cannot be predicted by the effects observed at high doses.”   This paper needs to be read by every regulating agency at the state and federal level because it opens the door to a new way of thinking about heath risks.  No longer is it enough or even good science to evaluate health risks using traditional dose response thinking that accepts effects at high doses, but not at low doses.

As noted in an earlier blog, Linda Birnbaum, director of the National Institute for Environmental Health Sciences, described this traditional approach to evaluating health risks as “antiquated” and that it needs to be replaced by a “better understanding of the actual characteristics of modern environmental chemicals.”  In a recent editorial Birnbaum says “It is time to start the conversation between environmental health scientists, toxicologists, and risk assessors to determine how our understanding of low doses effects and non-monotonic dose responses influence the way risk assessments a re performed for chemicals with endocrine disrupting activities.“

Birnbaum is right.  We need to begin rethinking how we evaluate health risks from low dose exposures to toxic chemicals.  For a copy of the Vandenberg paper see:

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New Dioxin Report: What it means

Several weeks ago EPA released the non-cancer portion of the EPA’s health assessment for the chemical known as dioxin. The event passed without industry collapsing, without the public going into panic as was anticipated by the food industry, and basically without the world coming to an end. The myriad forecasts of doom that industry and its apologists predicted did not come to pass. In fact, the media barely took notice. Why? – Because the reassessment did not set any new standards or introduce any new regulations.  It simply provided the scientific basis for determining the risks that dioxin poses, though in this case, just the non-cancer risks (EPA is still working on the cancer report).

The non-cancer effects of dioxin as described in the report are quite serious. In a recent review paper, Dr. Linda Birnbaum, Director of the NIEHS, summarized the adverse health effects of dioxin exposure in humans as including “cardiovascular disease, diabetes, cancer, porphyria, endometriosis, early menopause, reduced testosterone and thyroid hormones, altered immune responses, skin, tooth, and nail abnormalities, altered growth factor signaling, and altered metabolism.”

Most notably, the non-cancer assessment included for the first time a value called the reference dose.  This is a number used to evaluate non-cancer risks and is generally defined as “a level below which exposures are generally considered to be safe.” The EPA’s Reference Dose for dioxin is 0.7 picograms TEQ per kilogram per day (pg/kg/d) which was derived by evaluating developmental and reproductive effects in a community in Italy (Seveso) exposed to dioxin caused by an accident at a pesticide manufacturing plant.

What’s remarkable about the EPA reference dose is when you compare this number to the average daily exposure of the American public to dioxin (defined as the daily intake from all sources, 90% of which comes from food).  Using the most recent data from EPA (see Lorber et al. 2009) the average daily exposure is 0.54 pg TEQ/kg/d compared to EPA’s reference dose of 0.7 pg TEQ/kg/d.  So the average person gets a daily dose of dioxin that’s 77% of EPA’s new reference dose. That’s the good news; the bad news is that the average is so very close to the EPA reference dose and that some groups, especially children, are exposed to higher levels that exceed the new EPA reference dose. This is because children have different eating habits than adults. They tend to eat more diary products that are high in dioxin. Dioxin is prevalent in foods that are high in saturated fat, primarily meat and dairy.

A 2003 study conducted by a National Academy of Sciences Committee on Dioxin in Food bears this out. The committee found that children ages 1 to 5 were exposed to 1.09 pg TEQ/kg/day and children ages 6-11 years old were exposed to 0.69 pg TEQ/kg/day. This analysis shows that dioxin exposure in children 1 to 5 years old exceeds EPA’s reference or safe dose and that children 6 to 11 years old have dioxin exposure that is virtually identical to the EPA reference dose.

As a practical matter, this means that the best risk estimate we have on dioxin shows that the public, especially children are being exposed to unacceptable levels of dioxin that may be causing subtle adverse effects. These subtle effects likely include developmental effects that Dr. Birnbaum described in her review paper as posing the greatest concern “in part because the effects occur at the high end of the background range for the general population.”  These exposures may exceed the EPA’s reference does and even approach the levels observed in the study of Seveso, Italy.    The developmental effects may include altered thyroid and immune status, altered neurobehavior at the level of hearing, psychomotor function, and gender-related behaviors, altered cognition, dentition, and development of reproductive organs, and delays in breast development, in addition to altered sex ratios among exposed offspring.

While no exposure to dioxin is the ideal, we are not there yet.  In the meantime, exposure to dioxin in food, especially for children remains too high and needs to be addressed by EPA, FDA, and USDA. CHEJ strongly urges the EPA to finish and release their review on dioxin and cancer, and to develop a comprehensive action plan to further reduce dioxin emissions and exposures.

For a copy of EPA’s new dioxin health report, visit

To see CHEJ’s press release about this report, visit

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Who's Calling the Shots?

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Backyard Talk

Reducing Dioxin Exposure

As we approach the EPA’s self-imposed deadline at the end of January to complete the non cancer portion of the long awaited dioxin reassessment, there’s been a sudden rash of news stories about dioxin. One theme coming from the agriculture and food industry is that the diet of the American public will suffer because we will no longer be able to follow the Federal Dietary Guidelines often characterized as the food pyramid. Nothing could be further from the truth.  How is it that the industry just makes this stuff up?

Dioxin is a general term used to describe a family of over 200 chemicals that are not intentionally made.  Dioxins are unintentional by-products of numerous industrial processes such as paper, pesticide, and chemical manufacturing that include chlorine (such as PVC) and of combustion processes such as medical and municipal waste incineration.

Although dioxins are environmental contaminants, the American public is exposed primarily though our diet, with over 95% coming through dietary intake of animal fats, primarily meat and dairy. So the best way to reduce exposure to dioxin is to actually follow the advice in the Federal Dietary Guidelines which EPA readily acknowledges. These guidelines (see include the recommendations to choose a variety of meat and dairy products that are lean, low fat, or fat free, and to increase consumption of fruits, vegetables, and whole grain products. Meat, milk, and fish are important sources of nutrients and a balanced diet. Milk is a major source of calcium, vitamins A and D, and riboflavin; meat is an important source of iron, zinc and several B-vitamins; fish provides beneficial fatty acids as well as certain vitamins and minerals. Each of these foods provides high quality protein in the diet. Lean meat includes meats that are naturally lower in fat, and meat where visible fat has been trimmed. For fish and poultry you can reduce fat by removing the skin. Reducing the amount of butter or lard used in the preparation of foods and cooking methods that reduce fat (such as oven broiling) will also lower the risk of exposure to dioxin. These strategies will help lower the intake of saturated fats as well as reduce the risk of exposure to dioxin.

A report issued in 2003 by the Institute of Medicine (IOM) of the National Academies (formed when the issue of dioxin in food first came to light) came to a similar conclusion that following the dietary guidelines and limiting the intake of saturated fat would produce basic health benefits in addition to reducing dioxin exposures. Other key recommendations in the IOM report included reducing the contamination of animal feed and interrupting the recycling of dioxins that result from the use animal fat in feed products (see

More must be done to reduce industrial emissions of dioxins, but we can greatly reduce individual exposure by following the Federal Dietary Guidelines and reducing the intake of saturated fat by choosing meat and dairy products that are lean, low fat, or fat free, and by increasing consumption of fruits, vegetables, and whole grain products.