FEATURE ARTICLE
Assessing Risks from Bisphenol-A
Evaluating human health risks from endocrine disruptors such as BPA is difficult, but animal studies suggest trouble is afoot
Heather Patisaul
How Much Evidence is Enough?
Given this complex context, a clear, science-based strategy for identifying, screening and regulating suspected endocrine-disrupting compounds is badly needed. Nearly 40 years after DDT, the first recognized endocrine disruptor, was banned, new chemicals in the U.S. market are not routinely screened or tested for endocrine- disrupting properties. Congress created the Endocrine Disruptor Screening and Testing Advisory Committee in 1996 to recommend how the EPA should test and screen these compounds, but progress has been frustratingly slow. A list of compounds to be screened was not compiled until April of 2009, and it included only 67 chemicals, a tiny fraction of the thousands now suspected of having endocrine-disrupting properties. It also has not yet been determined how the screening should be conducted and which biological endpoints should be used.
It remains unclear how much evidence is needed to evaluate health risks from compounds such as BPA. The NTP used 261 publications to conclude that there is “some concern” regarding BPA exposure. The FDA, using far fewer, has so far insisted there is little to no risk. Who is right? Most of the studies used by the NTP were conducted in university laboratories. In contrast, the FDA relied mostly on data provided by industry. This schism occurred because the NTP reviewed scores of studies by academic scientists. In contrast, the FDA relies most heavily on studies conducted using a set of guidelines called “good laboratory practices” (GLP). These guidelines specify how data must be organized and deal mostly with quality assurance, but they do not necessarily assure good study design, use of appropriate controls or robust statistical analysis. GLP studies are expensive. Thus they are nearly all conducted by private industry or contract labs, not academic labs. U.S. health agencies need to update their risk assessment strategies so that all of the data being generated and analyzed by agencies such as NIH, FDA and EPA are coordinated, shared and given equal scrutiny.
Although research to date is not conclusive, there certainly is sufficient evidence to warrant concern about potential long-term effects from BPA exposure. Only a handful of studies have looked at associations between BPA exposure and disease outcomes in humans, some of which have found correlations. It is not ethically sound to expose people to a suspect compound and watch what happens. Even if it were, it would take many years for our slow-to-mature species to display any effects from the encounters. Research in animals, however, is robust. It indicates that BPA may disrupt reproductive tract development, sex-specific neuroendocrine circuitry and fertility, even at doses considered relevant for humans. Since laboratory animals are used in other aspects of human health research, including drug development, it is reasonable that evidence obtained from them should play a central role in any comprehensive human-risk assessment for BPA. When combined with human epidemiological studies, cell-culture assays and high-throughput genomic studies, evidence from experimental animals is likely the best tool we have to make predictions about human risk. That is especially true for the long-term consequences of early exposures during critical developmental windows.
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