Endocrine disrupting chemicals (EDCs).
A policy report from The Royal Society.
June 2000

[The full text of the report is available on-line as an Adobe Acrobat .pdf file.]
Press coverage in Nature

The Royal Society's report concludes with very cautious statements about the potential impacts of EDCs on humans, emphasizing the lack of data and the uncertainty about causation. It cites "strong evidence" linking EDCs to effects in wildlife. Despite the scientific caution, it takes a strong precautionary stance, recommending continued research, acknowledging that some of the public concerns about human impacts "already have some foundation" and suggesting that exposures, especially to pregnant women, be minimized. "Regulations cannot be 'put on hold' until all the evidence has been collected."

The report resembles the US National Academy of Sciences assessment in acknowledging that very few studies ("if any") have attempted to look for causal links between EDCs and reproductive effects in people. Hence the fact that there is no confirmation is a reflection of ignorance rather than one of safety. It differs from the NAS report, however, in that it takes a far more precautionary stance about recommended policies. The report states "It is preferable to establish the likely effects of EDCs on organisms in the environment in order to prevent damage, rather than wait until the damage has occurred and then try to establish the cause."

The report's main weakness is that it avoids the issue of low-dose impact. This allows it to conclude that EDCs are unlikely to cause many human effects at common levels of exposure, although the report qualifies that strongly by observing that only a limited number of compounds have been studied. It argues that because most identified EDCs in the environment have weak hormonal activity, human exposure would have to be high to cause effects. This gap in the report is perhaps understandable because of debates over whether some of the key low dose studies could be replicated. This was resolved affirmatively early during 2000, with published replication of Fred vom Saal's research. By this time, the Royal Society's report was most likely already in print.

Key points from the report's summary:

• "Humans are exposed daily to chemicals that have been shown, or suggested, to have hormone-disrupting properties. Speculation has linked this to a range of disorders. Whilst high levels of exposure to some EDCs could theoretically increase the risk of such disorders, no direct evidence is available at present. Trends in the incidence of some of these disorders are difficult to discern and when found, are difficult to interpret because of inconsistencies in method. EDCs are but one of a variety of potential risk factors, both environmental and genetic. Despite the uncertainty, it is prudent to minimize exposure of humans, especially pregnant women, to EDCs."
• "With regard to EDCs in the environment, firm assessment of the risk to humans is not possible because of a lack of relevant data about the effects of EDC exposure. On the basis of limited anaimal data, identified environmental EDCs appear to pose minimal risk to humans on their own, but the risk from mixtures of compounds is unknown."
• "Despite the lack of information on the effect on humans of EDCs in the environment, strong evidence links EDC exposure to effects on some organisms in the environment." ... "The action of EDCs has resulted in the localised destruction of certain species and is a cause for grave concern."
• "Increased effort should be focused on the identification of potential EDCs and the assessment of risk posed by individual chemicals, or by combinations of chemicals, supported by vigorous epidemiological studies."
• "While the issue of EDCs is confused by serious gaps in our knowledge, policies to deal with the current concerns must be developed," ... "hand in hand with ongoing research."

Other important points:

"New tests which will detect the endocrine-disrupting activities of chemicals are necessary," particularly to deal with "abnormalities of sexual differentiation/reproductive development where cause and consequence may be separated by a considerable period of time."

"In reality, humans are exposed not to a single endocrine disrupter but to a 'cocktail' of such chemicals, and the possibility that such chemicals have additive or reinforcing effects (e.g., combination of an oestrogenic with an anti-androgenic compound) has to be considered seriously. Using standard animal tests (acute toxicity tests) to evaluate these effects would be an extremely complex task with many potential problems."

The report has a good summary of the effects of tributyltin (TBT) on molluscs. It observes that these effects "were completely unexpected and unpredicted, despite legislation governinng new chemicals; nobody foresaw that TBT would cause endocrine disruption in molluscs." ... "This suggests that, until our understanding of how, and what, chemicals cause endocrine disruption improves very considerably, it is likely that other unexpected cases of endocrine disruption in wildlife will become apparent. This example also highlights the difficulty of predicting what effects a chemical will have in the wider environment where it may mix with other chemicals, get degraded, or come into contact with a variety of species of animals and plants."

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