Bisphenol A (BPA) : ABSTRACT
Bisphenol A (BPA) is a chemical that is primarily used in the production of polycarbonate (PC) plastic and epoxy resins. Around 1996, BPA began to attract considerable interest as a suspected endocrine-disrupting chemical. In this document, human health risks and ecological risks posed by BPA were assessed. Further, the economic impact of risk reduction activities was analyzed.
In the human health risk assessment, daily BPA intake was estimated by employing two different approaches. In the first approach, the exposure levels from possible sources (atmosphere, water, food, tableware, toys, etc.) were estimated and the values were combined. In the second approach, the daily BPA intake was determined from urinary excretion by backward calculations. In both the approaches, the parameters required for calculating the BPA intake were characterized as distributions; Monte Carlo simulations were performed to propagate uncertainty and variability in the parameters.
The key toxicological endpoints for human health risks posed by BPA were reduction in body weight gain, effects on the liver, and reproductive toxicity. The risks were characterized by using margin of exposures (MOEs) that were calculated by dividing NOAEL or BMDL by the daily BPA intakes. The MOEs were sufficiently large for all three endpoints even in case of individuals who had the highest BPA levels, i.e., children aged 1–6 years. It was concluded that the current BPA exposure levels were unlikely to pose unacceptable risks to human health.
In the ecological risk assessment, the following three assessment endpoints were selected to assess the impact of BPA on the sustainability of local populations of aquatic life, particularly fish: (1) survival, reproduction, growth, and development of susceptible aquatic species; (2) the growth rates of local fish populations including white-spotted char (Salvelinus leucomaenis), pale chub (Zacco platypus), Japanese dace (Tribolodon hakonensis), barbel steed (Hemibarbus barbus), and nekogigi (Pseudobagrus ichikawai); and (3) the presence and conditions of fish species confirmed by field observations in highly contaminated areas in Japan.
The analysis under assessment endpoint (1) indicated that ecological risks posed by BPA were below the level of concern in most areas. The analysis under assessment endpoint (2) confirmed that the five surrogate fish species were unlikely to face unacceptable risks in terms of population sustainability due to the current levels of BPA in ambient water. The analysis under assessment endpoint (3) proved that fish populations in rivers that were contaminated with up to 20 µg/L of BPA did not reach extinction readily. The results of assessment endpoints (2) and (3) were consistent with each other. Based on these considerations, it was concluded that the current exposure levels of BPA were unlikely to pose unacceptable risks to the local populations of aquatic life, particularly fish.
In the economic impact analysis of risk reduction activities, reduced daily BPA intakes and their costs were assessed for two activities: the substitution of PC tableware used for school lunches and the voluntary alternation of the method for inactivating the inner surface of drink cans. The substitution of PC tableware resulted in a reduction of daily BPA intake by 0.2–0.3 µg/kg/day. Its cost was estimated to be 127 yen per year per student or an annual cost of 370 million yen at the national level. The alternation of the method for inactivating the inner surface of drink cans resulted in a reduction of the daily BPA intake by 0.1–0.2 µg/kg/day for average-exposure individuals and 0.2–0.6 µg/kg/day for high-exposure individuals (95th percentiles). No facility investment was made only for reducing the migration of BPA from drink cans.
Bisphenol A Risk Assessment Document was produced under the Comprehensive Chemical Substance Assessment and Management Program funded by the New Energy and Industrial Technology Development Organization (NEDO).
The full text of Bisphenol A Risk Assessment Document (in Japanese) was published by Maruzen Co., Ltd. in November 2005.