Scientists will call on European leaders today to take urgent action to speed up regulation of the thousands of gender-bending chemicals in use across the continent.
The harmful effects of these chemicals - called endocrine disrupters - have been a growing concern in recent years but today's move will be the first time the scientific community has raised its concerns with politicians and the public at large.
The Prague Declaration, named after a meeting of more than 100 toxicologists and chemists in Czech Republic last month, and due to be launched today in Brussels, will state that legislation on the safe use of chemicals does not go far enough and lack of scientific evidence of the harmful effects of these chemicals must not delay political action.
"Many of these chemicals affect development in the womb," said Andreas Kortenkamp, a toxicologist at London University's School of Pharmacy and one of the signatories of the declaration. "The problem is that these effects are not captured in routine testing," he said.
Endocrine disrupters are a diverse group of several thousands of chemicals - such as polychlorinated biphenyls (PCBs) and dioxins - used in everything from pesticides to flame retardants, cosmetics to pharmaceuticals. Some of them alter the function of hormones in animals, either blocking their normal action or interfering with how they are made in the body. Since hormones regulate things like growth and body development, the potential for damage is clear.
The link between these chemicals and detrimental effects in wildlife is well-established: pseudo-hermaphrodite polar bears with penis-like stumps, panthers with atrophied testicles and male trout with eggs growing in their testes have all been documented as the probable result of endocrine-disrupting chemicals in the environment.
"Wildlife provides early warnings of effects produced by endocrine disrupters, which may as yet be unobserved in humans," the declaration said.
Scientists have long suspected that the presence of these chemicals is also responsible for the high prevalence of fertility problems in European men, and for the rise in the number of breast and testicular cancers.
Last month, scientists in America confirmed this fear with evidence that a class of chemicals known as phthalates - used to make plastics more pliable - may harm the development of unborn baby boys. Researchers had known for some time that high levels of these chemicals were harmful, but the latest study suggests that even normal levels - those commonly found in toys, plastic bags and clingfilm - could disrupt the development of male reproductive organs.
"Our interest is to highlight the need to deal with endocrine disrupters in EU regulation," said Dr Kortenkamp.
Forthcoming EU legislation on the safety of chemicals -known as Reach (Registration, Evaluation and Authorisation of Chemicals) - does have some clauses on endocrine disrupters, but scientists are concerned that the proposals do not go far enough.
They said that, while the EU has invested money into finding out how endocrine disrupters harm animals and plants, there has been little thought on what to do with the results.
Dr Kortenkamp said that there must be a more systematic approach to identifying and controlling the use of endocrine disrupters. "The level of proof required in Reach is far too high - it would only capture chemicals where it is more or less already proven that there are effects," he said.
"That is, in our opinion, not good enough. We feel we need to act pretty soon, even though some of the evidence isn't too hard cast."
Neither does Reach consider the potential cocktail effects of these chemicals. "If you continue evaluating chemicals one by one, you run the risk of erroneously concluding that there are no effects," said Dr Kortenkamp.
The declaration stops short of suggesting a ban on endocrine-disrupting chemicals. "Regulatory action can mean anything from labelling at the very soft end to banning at the very hard end," said Dr Kortenkamp.
