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Bisphenol A (BPA) is a high production volume chemical that is used in plastics and epoxy coatings. In 2015, California's Office of Environmental Health Hazard Assessment (OEHHA) added BPA to the Proposition 65 list of chemicals “known to cause reproductive toxicity” based on its Developmental and Reproductive Toxicant Identification Committee's (DART-IC) conclusion that BPA has been shown to cause female reproductive toxicity. A critical factor in determining compliance with Proposition 65 is a Maximum Allowable Dose Level (MADL), which is the exposure level at which a chemical would have no observable reproductive effect even if a person were exposed to 1000 times that level. We performed a comprehensive review of the literature, including the studies reviewed by DART-IC, and derived an oral MADL. Of all the studies we identified, Delclos et al. (2014) is of sufficient quality, has the lowest no observed effect level (NOEL), and results in the most conservative MADL of 157 μg/d. This is generally supported by other studies, including those that were considered by DART-IC. Also, the oral MADL provides a similar margin of safety as OEHHA's dermal MADL and other regulatory guidelines. Taken together, the scientific data support an oral MADL of 157 μg/d.

Ensuring adequate iodine intake is important, particularly among women of reproductive age, because iodine is necessary for early life development. Biologically based dose-response modeling of the relationships among iodide status, perchlorate dose, and thyroid hormone production in pregnant women has indicated that iodide intake has a profound effect on the likelihood that exposure to goitrogens will produce hypothyroxinemia. We evaluated the possibility of increasing iodine intake to offset potential risks from perchlorate exposure. We also explored the effect of dietary exposures to nitrate and thiocyanate on iodine uptake and thyroid hormone production. Our modeling indicates that the level of thyroid hormone perturbation associated with perchlorate exposures in the range of current regulatory limits is extremely small and would be overwhelmed by other goitrogen exposures. Our analysis also shows that microgram levels of iodine supplementation would be sufficient to prevent the goitrogenic effects of perchlorate exposure at current regulatory limits among at risk individuals. The human health risks from supplementing drinking water with iodine are negligible; therefore, this approach is worthy of regulatory consideration.