Introduction

Surveys show that the public suspects that synthetic (manmade) chemicals released into the environment, especially pesticides, have adverse effects on human health and cause disease, including cancer. In reality, few scientifically documented examples support this view, especially for effects on the general population.1 However, the observation that many synthetic chemicals have intrinsic hormonal activity—they are “endocrine disruptors”—has reopened this debate.1 Pressure groups have called for all synthetic environmental chemicals with the potential to cause harm to be phased out or banned, whereas the chemical industry argues that such action must be based on proof of harm. Vociferous cases have been made on both sides, each lacking definitive data. Yet it is clear that environmental and lifestyle factors are key determinants of human disease—accounting for perhaps 75% of most cancers.2 New understanding and emerging results are reshaping our thinking, as is the recognition that establishing cause and effect for environmental chemical exposures is a daunting task.

Methods and scope

Though this article is primarily an overview of the current evidence for reproductive effects resulting from exposure to environmental synthetic chemicals, it is relevant to the debate on wider potential health effects of such exposures. The review was compiled after detailed literature searches and cross referencing and scrutiny of relevant websites on environmental chemicals (see educational resources box). After revising the article in light of reviewers' comments, we sought the opinion of an expert toxicologist in industry to ensure balance in the review.

In this hugely contentious area, polarised opinions predominate (because of the lack of definitive data). There are enormous difficulties in establishing whether exposure to individual chemicals or to chemical mixtures causes harm, as adverse effects may not manifest until many years after exposure (for example, in adulthood after fetal exposure). This difficulty must be factored into any discussion of …