Brain drain: the cost of neglected responsibilities in evaluating cumulative effects of environmental chemicals.

Developmental disabilities affect millions of people and have a great impact on their lives, their families and the societies where they live. The prevalence of disorders such as autism, attention deficit hyperactivity disorder as well as subclinical decrements in brain function cannot be explained solely as genetic diseases. Exposures to environmental chemicals, especially during prenatal and early postnatal life, are one likely explanation for some of the decrements. The current chemical risk assessment approach is typically based on the toxicity caused by a single chemical on a variety of organs without acknowledging additional exposures to other chemicals also affecting the same organ or system. We identified more than 300 chemicals allowed in food that may have potential harmful effects on the developing brain. Each individual chemical may or may not have a harmful effect if it were the only one present, but we know next to nothing about their cumulative biological effects on the brain. An expanded cumulative risk assessment approach is needed, and it should focus on health outcomes, like developmental disabilities, arising from the accumulation of effects of multiple chemicals on the brain. The laws regulating the safety of additives already require that regulators in Europe and the USA consider cumulative effects; so far, they seem to have neglected the mandate. We must move beyond treating chemical exposures as isolated incidents and look at their cumulative biological effects on organs and their role in the onset of chronic diseases. The time has come to overhaul chemical risk assessment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.