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: