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Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

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Low Dose Effects

Scientific evidence now shows that some chemicals, especially endocrine disrupting compounds, can exert negative effects at extremely low levels of exposure - sometimes with more serious or different effects than at higher doses.

Except in cases of accidental or occupational exposures, most exposures to chemicals are at “very low doses.” Most chemical safety studies look at the toxic effects of higher doses of chemicals and then assume decreasing toxicity with lower doses. Yet substances that disrupt the body’s own hormones — known as endocrine-disrupting compounds (EDCs) — can exert important biological effects at low doses similar people’s real-life exposures. These effects are often qualitatively different from those found in traditional toxicology experiments. Low-dose effects are especially likely in developing tissues, during the formative periods when even minuscule levels of naturally occurring hormones determine the normal course of development (see Vandenberg et al., 2012 for an overview). EDC effects are often strongest at low doses at developmental stages when the complex hormonal regulation has not yet been established.

Nevertheless, there remains an ongoing “he said–she said” public argument about whether scientific findings really demonstrate that low doses of EDCs can have a damaging effect on human and animal health. Along with scores of other scientists and scientific organizations, we argue strongly that low-dose effects of EDCs have been demonstrated broadly, repeatedly and in many tissues and models, including developing mammary tissue (Vandenberg et al., 2012; Diamanti-Kandarakas et al., 2009; Welshons et al., 2003; PCP, 2010).