Potential oestrogenic or other hormone-mimicking effects of environmental chemicals have become a major concern in recent years. Firm scientfic evidence of effects exists in only a few instances. But in January, the Environment Agency urged industry to take precautionary action to limit environmental exposure to suspect compounds (ENDS Report 276, p 17-20 ).
The Agency's consultation paper asked industry to phase out or reduce discharges of a growing list of suspected endocrine disruptors. The list includes many pesticides and persistent organochlorine compounds, but also three groups of chemicals which are important products for the chemical industry - phthalate plasticisers used in PVC, alkyl phenol compounds such as alkyl phenol ethoxylates (APEs), and the plastics intermediate bisphenol A.
In April, the Agency held a consultation meeting on its proposals. CIA representative Elisabeth Surkovic promised to respond with a "lengthy summary" of its work which would "clear" key products of endocrine disruption effects.
The response was released in May. It tells the Agency that the CIA will only support "a precautionary approach based on weight of scientific risk assessment evidence." "The majority of recent reports suggest there is no evidence of a causal link", the CIA insists.
The paper received a hostile response from environmental groups. Gwynne Lyons of Worldwide Fund for Nature said: "For the CIA to say that it supports a precautionary approach but then demand a causal link is laughable. Such flawed logic only serves to discredit industry." Michael Warhurst of Friends of the Earth accused the industry of using humans and the environment as "guinea pigs" to test chemical products.
The industry's refusal to acknowledge the reality of endocrine effects met with an embarrassing public rebuttal at a press conference called by its European association CEFIC. Announcing a £4.3 million research programme (see below), the chairman of CEFIC's endocrine steering group, George Luckett, made repeated references to "the endocrine disruption hypothesis, prompting an interjection from a prominent endocrine scientist.
Dr Peter Matthiessen of the Ministry of Agriculture's Centre for Fisheries and Aquaculture Science told the conference that industry's use of the term "hypothesis" is inappropriate. "There is abundant evidence that wildlife is being affected.We are not [now] talking about a hypothesis."
The CIA paper includes reports from industry sector groups on APEs, phthalates and bisphenol A. The response of the European surfactants group CESIO amounts to a denial that there is a problem with APEs - despite endocrine-disrupting effects being demonstrated in fish. Controls on the compounds may be in the pipeline at EC level following a UK-led risk assessment (see pp 3-4 ).
CESIO believes it "inappropriate" for the Agency to identify APEs as priority substances, claiming that both they and their alkyl phenol breakdown products are "easily removed in properly operating sewage works." As evidence, it cites studies sponsored by the industry - but these contradict independent research showing that APEs degrade incompletely to a mixture of oestrogenic products.
The group also questioned Environment Agency studies on the river Aire in Yorkshire which found persistent endocrine- disrupting effects in fish due to APE discharges from wool scouring companies (ENDS Report 246, pp 5-6 ). "The data do not clearly demonstrate that APEs are the primary cause," CESIO quibbled, preferring to shift the argument to the more widespread but less persistent effects the Agency has uncovered due to natural steroids present in sewage effluents.
The report on phthalates notes that experiments carried out by Dr Richard Sharpe which found reproductive effects in rats at low doses have not proved repeatable (ENDS Report 268, pp 26-29 ). It also points out that the "vast majority" of phthalates are inactive in in vitro assays for oestrogenicity. Some key compounds have proved positive, but the focus of interest in phthalate toxicity has shifted from oestrogenic to anti-androgenic activity (see below).
High phthalate doses given to laboratory rodents caused liver cancers and reproductive disfunction, the report concedes - effects which have been a focus of concern over exposure from soft PVC baby toys (see pp 30-31 ). However, humans are less sensitive and exposed to much lower levels. The paper concludes that phthalates "pose no significant.threat to humans."
The industry report on bisphenol A says that releases to the environment are "small and unlikely to be widespread," and that the compound is "readily biodegradable" and "poses minimal risk to the environment." However, one of the key issues in the endocrine disruption debate is the recently reported discovery by US researchers that very low doses of bisphenol A can cause permanent increases in the prostate size of young mice (ENDS Report 266, pp 8-9 ).
These studies have recently been extended to cover other reproductive characteristics.1 Researchers led by Professor vom Saal found that a very low dose of bisphenol A (2ng/g body weight) either reduced or enlarged organs in the male reproductive tract, while a dose ten times higher permanently reduced sperm count by 20%.
The industry says that such results are inconsistent with its own studies which show "no adverse carcinogenic, developmental or reproductive effects." It is seeking to repeat Professor vom Saal's research, describing it as "preliminary" because of the "very small" number of animals and doses used.
Another programme on endocrine disruption in the marine environment - known as EDMAR - will look for biomarkers and population level effects in marine species. Other projects will attempt to identify the substances responsible and their sources. It will be mainly funded by MAFF and the DETR, with contributions from government agencies and CEFIC.
Dibutyl phthalate (DBP) can affect the development of the male reproductive system in rats at a level which produces no toxic effects in the mother, Dr Paul Foster of the US Chemical Industry Institute of Toxicology reported at an IBC conference in London in May. He believes that the effects - which included reductions in testis size and fertility and undescended testes - are consistent with hypotheses linking chemical exposure in early life to declines in male fertility.
The effects are due to anti-androgenic rather than oestrogenic action, said Dr Foster, but the doses required were well in excess of those reported to be effective in earlier studies by Dr Sharpe. Dr Foster's work suggests a tolerable human daily intake of DBP of about 66mg/kg bodyweight per day in humans - similar to that proposed by the EC Scientific Committee on Food. This is well above reported DBP intakes, but dietary studies suggest that total phthalate exposure could approach this in high-level consumers (ENDS Report 255, pp 5-6 ).