Norbert Caspers

A Weight of Evidence Approach to the Aquatic Hazard Assessment of Bisphenoi A

Bisphenol A (BPA; 4,4-isopropylidene diphenol) is a chemical intermediate used primarily in the production of epoxy resins and polycarbonate products. BPA has been identified in surface waters and, hence, has been the subject of considerable research into its potential effects on aquatic organisms. Available literature on the aquatic toxicity of BPA was reviewed for quality against European Union TGD and Organization of Economic Cooperation and Development GLP principles. From this review, studies of suitable quality covering numerous ecologically relevant endpoints were identified to evaluate the survival, growth, and reproductive success of aquatic organisms exposed to BPA. Those studies yielded approximately 70 no observed effect concentrations (ranging from 16 to 3640 μg/L) and lowest observed effect concentrations (160 to 11,000 μg/L) that were considered in this weight of evidence assessment. Across all data, adverse effects on survival, growth, and reproduction occurred only at concentrations of 160 μg/L and above. Secondary biochemical (e.g., vitellogenin induction) and morphological (e.g., gonad histology) data provide insight into mechanisms of action, but do not correlate with apical endpoints related to survival, growth, and reproduction. Comparing the weight of the evidence of the aquatic toxicity data that showed chronic effects at 160 μg/L and higher with typical surface water concentrations in the range of 0.001 to 0.10 μg/ L, BPA is unlikely to cause adverse effects on aquatic populations or ecosystems.

Early life-stage and multigeneration toxicity study with bisphenol A and fathead minnows (Pimephales promelas).

Regulatory guidelines for long term testing to assess the toxicity of xenobiotic compounds such as bisphenol A (BPA) with fish have focused on survival, growth, and development in early life stages. Early life stages are critical windows of exposure, but do not address later phases in the life cycle, such as reproduction, that are equally important for the continued survival of the organisms. Residual amounts of BPA are released to surface water. BPA has, therefore, been the subject of considerable toxicity testing with fish and other aquatic organisms. A long term multigeneration test with fish has been conducted to better interpret the environmental relevance of detectable levels of BPA. Fathead minnow (Pimephales promelas) were exposed for 444 days over the course of three generations that included F0 reproducing adults, F1 eggs grown to be reproducing adults, and F2 eggs. Endpoints included survival, growth, reproduction, and vitellogenin concentrations. Concentrations tested ranged from 1 to 1,280 μg/L. No observed effect concentrations (NOEC) of 640 μg/L and higher for growth parameters show few differences between age or generation. Reproductive NOEC in F0 and F1 breeding pairs were 640 and 160 μg/L, respectively. The lowest NOEC related to survival, growth and development or reproduction was 16 μg/L for F2 hatching success. This long term study covered both early life and adult reproduction stages that allowed examination of all critical windows of exposure. Overall, NOEC ranging from 16 to 1,280 μg/L were found, which are well above median and upper 95th percentile concentrations of BPA in fresh waters in North America and Europe (0.081 and 0.47 μg/L and 0.01 and 0.035 μg/L, respectively). The likelihood is low that measured concentrations of BPA in surface water would affect fish, even if exposed over more than one generation.

Relevance of drinking water as a source of human exposure to bisphenol A

A comprehensive search of studies describing bisphenol A (BPA) concentrations in drinking water and source waters (i.e., surface water and groundwater) was conducted to evaluate the relevance of drinking water as a source of human exposure and risk. Data from 65 papers were evaluated from North America (31), Europe (17), and Asia (17). The fraction of drinking water measurements reported as less than the detection limit is high; 95%, 48%, and 41%, for North America, Europe, and Asia, respectively. The maximum quantified (in excess of the detection limit) BPA concentrations from North America, Europe, and Asia are 0.099 μg/l, 0.014 μg/l, and 0.317 μg/l. The highest quantified median and 95th percentile concentrations of BPA in Asian drinking water are 0.026 μg/l and 0.19 μg/l, while high detection limits restricted the determination of representative median and 95th percentile concentrations in North America and Europe. BPA in drinking water represents a minor component of overall human exposure, and compared with the lowest available oral toxicity benchmark of 16 μg/kg-bw/day (includes an uncertainty factor of 300) gives margins of safety >1100. Human biomonitoring data indicate that ingestion of drinking water represents <2.8% of the total intake of BPA.

Estimating potential risks to terrestrial invertebrates and plants exposed to bisphenol A in soil amended with activated sludge biosolids.

Bisphenol A (BPA) is a high production volume substance primarily used to produce polycarbonate plastic and epoxy resins. During manufacture and use, BPA may enter wastewater treatment plants. During treatment, BPA may become adsorbed to activated sludge biosolids, which may expose soil organisms to BPA if added to soil as an amendment. To evaluate potential risks to organisms that make up the base of the terrestrial food web (i.e., invertebrates and plants) in accordance with international regulatory practice, toxicity tests were conducted with potworms (Enchytraeids) and springtails (Collembolans) in artificial soil, and six plant types using natural soil. No-observed-effect concentrations (NOEC) for potworms and springtails were equal to or greater than 100 and equal to or greater than 500 mg/kg (dry wt), respectively. The lowest organic matter-normalized NOEC among all tests (dry shoot weight of tomatoes) was 37 mg/kg-dry weight. Dividing by an assessment factor of 10, a predicted-no-effect concentration in soil (PNEC(soil)) of 3.7 mg/kg-dry weight was calculated. Following international regulatory guidance, BPA concentrations in soil hypothetically amended with biosolids were calculated using published BPA concentrations in biosolids. The upper 95th percentile BPA biosolids concentration in North America is 14.2 mg/kg-dry weight, and in Europe is 95 mg/kg-dry weight. Based on recommended biosolids application rates, predicted BPA concentrations in soil (PEC(soil)) would be 0.021 mg/kg-dry weight for North America and 0.14 mg/kg-dry weight for Europe. Hazard quotients (ratio of PEC(soil) and PNEC(soil)) for BPA were all equal to or less than 0.04. This indicates that risks to representative invertebrates and plants at the base of the terrestrial food web are low if exposed to BPA in soil amended with activated sludge biosolids.

Effects of husbandry parameters on the life-history traits of the apple snail, Marisa cornuarietis : Effects of temperature, photoperiod, and population density

These experiments are part of a larger study designed to investigate the influence of husbandry parameters on the life history of the apple snail, Marisa cornuarietis. The overall objective of the program is to identify suitable husbandry conditions for maintaining multi-generation populations of this species in the laboratory for use in ecotoxicological testing. In this article, we focus on the effects of photoperiod, temperature, and population density on adult fecundity and juvenile growth. Increasing photoperiod from 12 to 16 h of light per day had no effect on adult fecundity or egg hatching and relatively minor effects on juvenile growth and development. Rearing snails at temperatures between 22°C and 28°C did not influence the rates of egg production or egg clutch size. However, the rates of growth and development (of eggs and juveniles) increased with increasing temperature in this range, and when temperatures were reduced to 22°C egg-hatching success was impaired. Juvenile growth and development were more sensitive to rearing density than adult fecundity traits. On the basis of the present results, we conclude that rearing individuals of M. cornuarietis at a temperature of 25°C, a photoperiod of 12L:12D, and a density of <0.8 snails L−1 (with lower densities for juvenile snails) should provide favorable husbandry conditions for maintaining multi-generation populations of this species.

Comparison of Four Species Sensitivity Distribution Methods to Calculate Predicted No Effect Concentrations for Bisphenol A

ABSTRACT Bisphenol A (BPA, CAS RN 80-05-7) is a high production volume chemical used as an intermediate in the production of polycarbonate plastic and epoxy resins. During its manufacture and use, some emissions to surface waters are anticipated. Chronic predicted no effect concentrations (PNECs) for aquatic systems are used to support the assessment of potential risks to aquatic organisms in receiving waters. PNECs for a compound are considered protective of populations, communities, and ecosystems. Traditionally, PNECs are derived by taking the lowest no-observed effect concentration (NOEC) from a set of toxicity studies and dividing by an assessment factor (e.g., 10 to 1000). This traditional approach is appropriate for substances with few data, but may not be necessary for substances with many valid studies. For well-studied substances, statistical approaches (i.e., development of Species Sensitivity Distribution or SSD methods) can be used to calculate a PNEC that makes use of the full distribution of available NOEC values. Bisphenol A has an extensive set of aquatic toxicity studies covering diverse taxa including algae, hydra, rotifers, mollusks, crustaceans (both benthic and pelagic), insects, annelids, fish, and amphibians. The full chronic data set was used to calculate PNEC values using four SSD methods: (1) the Hazard Concentration (HC5) approach developed by The Netherlands National Institute of Public Health and the Environment (RIVM), (2) the U.S. Environmental Protection Agencys water quality criteria procedure, (3) SigmaPlot (Systat 2000) commercial software that calculates percentile values, and (4) a distributional method consistent with that used by Environment Canada. Using these approaches, PNEC values for BPA range from 11 to 71 μ g/L. Literature studies suggest that application of an additional assessment factor is unwarranted if an SSD-based PNEC is based on chronic data. SSD-derived PNEC values and the traditionally derived PNEC value of 1.6 μ g/L are then compared to concentrations of BPA that have been measured in North American and European surface waters. Adverse risks to aquatic organisms are not anticipated from measured concentrations of BPA in North American and European surface waters.

Effects of bisphenol A on fecundity, egg hatchability, and juvenile growth of Marisa cornuarietis

Recent work on the snail Marisa cornuarietis has claimed to show endocrine disruption in response to bisphenol A (BPA). The present experimental design was optimized to detect effects of BPA on fecundity, egg hatchability, and juvenile growth, with an emphasis on reproduction, since previous studies suggested this to be a sensitive endpoint. No differences in eggs/female/ month between unexposed snails and snails exposed to nominal concentrations of 0.1, 1, 25, and 640 microg BPA/L during six months of exposure were found. No effect of BPA on the percentage of eggs hatching successfully was found, as was no difference in time to hatching between the control and any BPA treatment. We observed a significant decrease in female growth and a marginal effect on female wet weight in the 640-microg/L treatment compared to the control and a significant increase in male growth rate and a marginal increase in male wet weight in the 1-microg/L treatment compared to the control. However, a much greater proportion of the variability in juvenile growth was explained by variation between pairs and between siblings from the same pair than by BPA treatment. We conclude that effects of BPA in the nominal exposure range 0.1 to 640 microg/L (measured range 0.062-696 microg/L) are unlikely to be of significance for field populations of this species. An additional adult fecundity trial at 22 degrees C (in contrast to all other experiments that were conducted at 25 degrees C) found no evidence to suggest that snails are more sensitive to BPA at the lower temperature, as has been previously claimed. The present results indicate that the sensitivity of M. cornuarietis to BPA is similar to that of other aquatic invertebrates for which data are available.

Effects of food type, feeding frequency, and temperature on juvenile survival and growth of Marisa cornuarietis (Mollusca: Gastropoda)

The present experiments are part of a larger study designed to investigate the influence of husbandry parameters on the life history of the ramshorn snail, Marisa cornuarietis, in order to identify suitable husbandry conditions for maintaining multi-generation populations in the laboratory for use in ecotoxicological testing. In this paper we focus on the effects of a combination of food types and feeding frequencies (i.e., the frequency with which the snails were offered food) on juvenile growth and survival at different temperatures. Offspring produced in the laboratory by wild specimens of M. cornuarietis, from Puerto Rico, were used to test the effects of three types of food (lettuce, alginate with fish food, alginate with snail mix) fed at three frequencies (given ad libitum on 4/4, 2/4, or 1/4 d) on juvenile survival and growth. The 4-d feeding regimens were repeated four times, giving a total of 16 d for the experiments. The experiments were conducted at two temperatures (22° and 25°C) under a 12 h light:12 h dark photoperiod. Juvenile growth rates increased with increasing feeding frequency for all food types. The most rapid growth rates occurred in the high-frequency lettuce treatments and the slowest growth rates in the low-frequency lettuce and alginate with snail mix treatments. Juvenile snails grew faster at 25° than at 22°C, and mortality was about twice as high at the lower temperature. Growth rates were used to provide a rough estimate of time to maturity, which was determined to take about twice as long at 22° than at 25°C. The results showed that lettuce is the best food if supplied in abundance, but effects on growth are very dependent on feeding frequency and temperature. We conclude that 25°C is a more appropriate temperature for maintaining populations than 22°C, that lettuce provides a suitable food source, and that food should be supplied continuously for husbandry and toxicity testing of populations of M. cornuarietis.

Adult fathead minnow, Pimephales promelas, partial life-cycle reproductive and gonadal histopathology study with bisphenol A.

Bisphenol A (BPA) is an intermediate used to produce epoxy resins and polycarbonate plastics. Although BPA degrades rapidly in the environment with aquatic half-lives from 0.5 to 6 d, it can be found in aquatic systems because of widespread use. To evaluate potential effects from chronic exposure, fathead minnows were exposed for 164 d to nominal concentrations of 1, 16, 64, 160, and 640 µg/L BPA. Population-level endpoints of survival, growth, and reproduction were assessed with supplemental endpoints (e.g., vitellogenin, gonad histology), including gonad cell type assessment and quantification. No statistically significant changes in growth, gonad weight, gonadosomatic index, or reproduction variables (e.g., number of eggs and spawns, hatchability) were observed; however, there was a significant impact on male survival at 640 µg/L. Vitellogenin increased in both sexes at 64 µg/L or higher. Gonad cell type frequencies were significantly different from controls at 160 µg/L or higher in males with a slight decrease in spermatocytes compared with less mature cell types, and at 640 µg/L in females with a slight decrease in early vitellogenic cells compared with less mature cells. The decrease in spermatocytes did not correspond to a decrease in the most mature sex cell type (spermatozoa) and did not impair male fertility, as hatchability was not impacted. Overall, marginal shifts in gametogenic cell maturation were not associated with any statistically significant effects on population-relevant reproductive endpoints (growth, fecundity, and hatchability) at any concentration tested.

Characterizing the effects of bisphenol A on sediment‐dwelling benthic organisms

Bisphenol A (BPA) is a high production volume chemical intermediate used primarily in the production of polycarbonate plastics and epoxy resins. It primarily enters surface water and sediment via effluent discharges during its manufacture and use. The physical properties of BPA suggest that sediment is a potential sink and may result in exposure to benthic organisms. Currently there are no studies measuring the chronic toxicity of BPA to benthic organisms via direct sediment exposure. The present study examined the chronic toxicity of BPA to 3 commonly used test organisms that are generally representative of invertebrates occupying the base of the benthic food web and for which standardized testing protocols are available: the oligochaete Lumbriculus variegatus (mean numbers and biomass), the midge Chironomus riparius (emergence and development rate), and the estuarine amphipod Leptocheirus plumulosus (survival, growth, and reproduction). No-observed-effect concentrations (NOECs) for the 3 species ranged from 12 mg/kg to 54 mg/kg dry weight. All NOEC values were higher than all measured concentrations of BPA in freshwater and marine sediments reported in reliable, fully reported studies from North America and Europe from the 1990s to the present. For the first time, there are studies with BPA measuring the chronic toxicity to 3 taxa of sediment dwelling invertebrates, which are suitable to support region-specific risk assessments.