The evidence for endocrine disruption in humans
Establishing a link between endocrine disruptors and human health is complicated by the fact that experiments of the kind conducted on animals are out of the question. It would be wholly unethical to administer DDT to people, for example, to see what effects it had on them. Studies on humans are thus limited to establishing a correlation between the presence of a xenobiotic chemical in the environment and some kind of health problem.
For example, the Aamjiwnaang are a community of Native Americans who live next to a major chemical complex in Ontario, Canada. Over the years, the ratio of boys and girls born in this community has been changing, from equal numbers in the period 1984–88 to 46 boys and 86 girls in 1999–2003. High levels of phthalates and hexachlorobenzene, both known to have endocrine-disrupting properties, have been found in the local soil (Mackenzie et al., 2005). Such data are suggestive of a causal link between endocrine-disrupting chemicals and a changed sex ratio, but do not provide conclusive proof for such a link. There may be other reasons why the sex ratio has changed.
By 2006, over 50 chemical compounds had been identified as endocrine disruptors. Many of these are long-lived compounds that can persist in the environment for many years without being degraded, and which can bioaccumulate in body tissues. They include several herbicides (e.g. atrazine), fungicides and insecticides (e.g. DDT); industrial chemicals and by-products such as PCBs and dioxin; and a number of compounds found in plastics, such as phthalates and styrenes, that are used to package foods and drinks (WRI, 1999). Levels of endocrine disruptors are especially high in heavily urbanised areas of the world.