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Research on the Effects on Neurological Development by Endocrine Disrupting Chemicals

EPA scientists are researching how endocrine disrupting chemicals affect the brain and nervous system

Endocrine disrupting chemicals can affect multiple systems in the body, including the brain and nervous system. One way chemicals affect the brain is through disrupting the levels of thyroid hormones - one of the main hormone systems that interests EPA's Endocrine Disruptor Screening Program.

These hormones help control the development and maturation of the central nervous system. EPA scientists have found reductions in thyroid hormones in rats exposed in utero to ammonium perchlorate, a component of rocket fuel and an environmental contaminant. The quantitative relationship between reductions in thyroid hormones and neurological effects has yet to be precisely defined.

EPA scientists are currently researching:

  • the degree to which thyroid hormones must be reduced before neurological effects begin to emerge,
  • the timing and duration over which exposure must occur to induce them, and
  • the most sensitive endpoints for detection.

EPA scientists have found neuronal effects in offspring of pregnant rats who experienced reductions in serum hormone of less than 25 percent.

Scientists also identified new methods to assess effects on the nervous system, which could reduce the reliance on behavioral assessments of neuro development. These new methods include:

  • imaging techniques to determine the effects on the brain,
  • identifying subtle abnormalities in brain structure, and
  • examining the disruption of thyroid-sensitive genes in the brain.

Measurements generated from these methods may be more readily translated into computational models that can be used to make predictions about the neurological effects of chemicals. The research will help EPA prioritize which chemicals need animal testing and which tests are most appropriate for different types of chemicals.