The impact of endocrine disrupting chemical (EDC) exposure on human health is receiving increasingly focused attention. The prototypical EDC bisphenol A (BPA) is an estrogenic high-production chemical used primarily as a monomer for the production of polycarbonate and epoxy resins. It is now well established that there is ubiquitous human exposure to BPA. In the general population, exposure to BPA occurs mainly by consumption of contaminated foods and beverages that have contacted epoxy resins or polycarbonate plastics. To test the hypothesis that bioactive BPA was released from polycarbonate bottles used for consumption of water and other beverages, we evaluated whether BPA migrated into water stored in new or used high-quality polycarbonate bottles used by consumers. Using a sensitive and quantitative competitive enzyme-linked immunosorbent assay, BPA was found to migrate from polycarbonate water bottles at rates ranging from 0.20 ng/h to 0.79 ng/h. At room temperature the migration of BPA was independent of whether or not the bottle had been previously used. Exposure to boiling water (100 degrees C) increased the rate of BPA migration by up to 55-fold. The estrogenic bioactivity of the BPA-like immunoreactivity released into the water samples was confirmed using an in vitro assay of rapid estrogen signaling and neurotoxicity in developing cerebellar neurons. The amounts of BPA found to migrate from polycarbonate drinking bottles should be considered as a contributing source to the total "EDC-burden" to which some individuals are exposed.

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Summary• Phosphorus (P)-limited plants produce higher amounts of root phosphatases, but research has mostly focused on phosphomonoesterases (PMEs). Because phosphate diesters can form a significant proportion of organic P in wetlands, we aimed to determine whether wetland plants produce both root PMEs and root phosphodiesterases (PDEs), and, if so, what factors influence activities of these enzymes.• We measured the activities of root PMEs and PDEs colorimetrically in a wide range of macrophytes from natural and P-enriched wetlands. Hydrolyzable P in sediments was analyzed using commercially available PMEs and PDEs.• In all species, both root PMEs and PDEs were always present, and their activities were closely correlated. Sedges and broadleaved emergents had the highest activity of both enzymes, while those of floating-leaved plants were the lowest. Redundancy analysis revealed close association between root enzymes and the proportion of monoesterase-and diesterase-hydrolyzable dissolved unreactive P. Both enzymes were positively correlated with root tissue N : P ratio.• Both plant and sediment traits were important when explaining differences in enzyme activities. Although the activities are related to ambient P regime, the relationship was not close enough to use root enzymes as reliable predictors of dissolved unreactive P that is hydrolyzed by sediment phosphomono-and diesterases.

Community respiration and nutrient limitation are frequently studied in pelagic habitats; however, comparisons of these processes between littoral and pelagic habitats are less common and do not exist from mountain lake ecosystems in the tropics. Community respiration was measured in the littoral benthic and pelagic habitats of a deep, endorheic mountain lake in Guatemala. Community respiration rates were quantified using biochemical oxygen demand within a temperature controlled, dark, laboratory incubation. Community respiration was measured in the pelagic habitat in response to inorganic nitrogen, phosphorus, nitrogen and phosphorus, glucose, five different soils, and sewage additions and in the littoral habitat in response to inorganic nitrogen, phosphorus, nitrogen and phosphorus, and sewage additions. During all periods, community respiration was higher and more variable in the littoral habitat than in the pelagic habitat. The additions of nitrogen, phosphorus, and nitrogen and phosphorus had no effect on community respiration, in either habitat. Glucose and four of the five soil additions from various watershed vegetation types significantly stimulated community respiration in the pelagic habitat. Sewage additions elicited the highest response in both pelagic and littoral habitats. We demonstrate that community respiration in a tropical montane lake is not limited by inorganic nitrogen or phosphorus and is not colimited by both nutrients combined. Treatments containing organic carbon and organic nutrients were significant stimulators of community respiration; therefore, organic carbon is likely limiting community respiration in Lake Atitlán.