Smart discussion about toxics policy reform

What Toxicology Won’t Measure – And What To Do

First in a series of guest blogs by best-selling author Daniel Goleman

I’ve got some bad news. Toxicology seems to have a blind spot when it comes to the stew of chemicals we breathe, drink or otherwise absorb over the course of life.

Currently federal standards for determining toxicity are based on whether single exposures to a specific chemical cause a given medical problem. But growing bodies of medical evidence suggest that the cumulative tiny doses of chemicals we encounter over our lifetime can add up to disease.

For instance, Deborah Cory-Slechta, a toxicologist at the Robert Wood Johnson Medical School, found that exposing lab animals to two common pesticides, paraquat and maneb, caused degeneration in the dopamine circuits that underlie Parkinson’s disease in humans. The damage only occurred if the exposure to one of the compounds was repeated (in this case, in the womb and again in adulthood), or to both pesticides in combination. Paraquat and maneb are quite distinct molecules, but the mixture or number or exposures produced the signature damage for Parkinson’s.

Such findings – and there are dozens of others like these – create a challenge for toxicology: an exposure just once to one of these chemicals resulted in no discernible damage.  And up to this point that method – assessing the damage from exposure to a single chemical or class of chemicals for a limited time – has been the gold standard in tests of a chemical’s toxicity, our early warning system for protection.

But that method tells us nothing about how a given chemical might cause damage if we are exposed to it in combination with others, or over a lifespan. The reality is that we all are exposed to a mix of countless chemicals continually, a predicament for which toxicologists have as yet no assessment method.

Here is the toxicologist’s dilemma: The standard methods for assessing safe levels of exposure to a chemical fail to address the environmental realities. Interactions among synthetic chemicals lodged in our bodies defy basic assumptions underlying toxicology risk analysis.

Standard tests assess whether a compound kills cells. But very low doses may fail to kill cells while nevertheless damaging the cells’ ability to function properly. Worse, a single-chemical, one-time exposure in healthy adults tells us nothing about how a substance might affect children, the chronically ill or the aged — groups with greater susceptibility to harmful chemical impacts. And what happens when we breathe polluted air, a mixture of countless varieties of ultra-fine particles whose chemical composition varies from place to place and day to day?

Cory-Slechta says neurotoxicology should adopt a “multi-hit” model, in which insults to different target sites — either over time from one molecule or all at once from many — harm a biological system. That would be in keeping with toxicology’s main mission, safeguarding human health.

So what are we to do in the meantime?

Try the precautionary principle: Find out what’s actually in all the stuff we eat, put on our bodies or otherwise are exposed to, and avoid the bad ones. Use Environmental Working Group’s Skin Deep database, for example, to learn the truth about the chemicals in personal care products.

If each of us did three things, it could actually get companies to get rid of all those toxic chemicals:

  1. Know the true ecological impacts of what we buy.
  2. Favor improvements.
  3. Tell everyone we know.

Those three steps, if taken by enough shoppers, would shift the market share of products enough to get the attention of companies. The more we make it pay to drop toxic chemicals from products, the more efforts corporations will put into developing safer alternatives and giving their business to suppliers who innovate to find safer ingredients.

Economists call this a “virtuous cycle,” where sound information in the marketplace lets shoppers be smarter about their choices. That, in turn, creates a bottom-line incentive for companies to do the right thing. Let’s make virtue pay.

[Adapted from Daniel Goleman, Ecological Intelligence: The Hidden Impacts of What We Buy. Daniel Goleman blogs at, and his conversations with experts on ecological transparency can be heard at:]

Next Monday: What We Don’t Know About the Toxic Stuff Around Us

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One Response to “What Toxicology Won’t Measure – And What To Do”

  1. Charli says:

    Thanks Mr. Goleman, for posting this. I think you hit a lot of key issues toxicologists face. In addition to what you outlined a major reason we are in this predicament is due to an emphasis on gathering data based on animals.

    Currently, many toxicity tests are based on experiments in animals and use methods that were developed as long ago as the 1930’s; they and are slow, inaccurate, open to uncertainty and manipulation, and do not adequately protect human health, just as you state. These tests take anywhere from months to years, and tens of thousands to millions of dollars to perform. More importantly, the current testing paradigm has a poor record in predicting effects in humans and an even poorer record in leading to actual regulation of dangerous chemicals.

    However, alternatives to animal testing exist in a powerful way and many scientists advocate them. From what I’ve read, the blueprint for development and implementation of alternatives to animal testing is the National Research Council report, Toxicity Testing in the 21st Century: A Vision and a Strategy in 2007. In this report scientists from the EPA and NIH state:

    A suite of these tests would replace a single animal test. Each test in the suite would measure different changes that occur in response to a chemical, giving a comprehensive picture of the affect the chemical may have on normal cell and tissue function. These test methods can be automated, so scientists can use machines to test hundreds and even thousands of chemicals at the same time, monitoring most of the possible effects on cells, tissues, and organs resulting from exposure to each chemical…Using this approach, regulatory scientists can simultaneously examine numerous possible health effects of exposure to thousands of chemicals.

    Decreasing our reliance on animal-based tests and putting time, energy, and money into human-relevant, non-animal based tests will allow us to move past the problems we’re currently experiencing and into an age where we can more effectively serve humans, animals, and the environment.