• ENDOCRINOLOGY
• ENVIRONMENTAL HEALTH
• PUBLIC HEALTH
• RESEARCH METHODS
• TOXICOLOGY

Since 2009 the European Commission (EC) is seeking a legal definition of endocrine disrupting chemicals (EDCs). These compounds ‘interfere with any aspect of hormone action’, and by doing so can adversely affect physiology and development and thus increase the risk of metabolic and reproductive disorders as well as hormone-sensitive carcinogenesis and impaired neurodevelopment.1 Accordingly, EDCs put a considerable burden on public health and public healthcare. In the European Union, they have been attributed to healthcare costs of €160 billion annually.2

The quality of an EDC definition has profound consequences for the regulation of economically important chemicals such as pesticides. An inclusive definition putting weight on a low burden of scientific proof will ultimately benefit public health and spark the innovation of ‘safe’ chemicals, some say. An exclusive definition requiring strong scientific evidence to pin EDCs down is preferred by others to minimise economic damage. After the process of defining what an EDC is has been substantially delayed by corporate lobbyism, scientists writing open letters and lawsuits by member states, the EC has in June 2016 decided in favour of the latter.

Amid a discourse driven by strategic rather than scientific deliberations, the main challenge of the EDC issue concerns complexity and thus remains at the centre of science. Out of the universe of chemicals, an unknown number of compounds have endocrine disrupting properties. Humans and wildlife are exposed to these chemicals via multiple routes from diverse sources. The dose and timing of exposure is dynamic and results in changing mixtures being subjected to multiple toxicokinetic and inducing multiple toxicodynamic processes eventually resulting in disease (sometimes decades after exposure). Co-exposure to other environmental stressors as well as interindividual differences add to the complexity.