Biomonitoring Equivalents for ethylene thiourea.

Ethylene thiourea, or ETU, is used in the rubber industry and is a degradation product and impurity in some fungicides. The general public may be exposed to low concentrations of residues of ETU in a variety of ways, including food treated with ethylene bis-dithiocarbamate (EBDC) fungicides or migration from rubber products. Biomonitoring of ETU in urine is useful for an assessment of integrated exposures to ETU across different sources and routes of exposure. In this evaluation, we review available health-based risk assessments and toxicological reference values (TRVs) for ETU and derive Biomonitoring Equivalent (BE) values for interpretation of population biomonitoring data. BEs were derived based on existing TRVs derived by Health Canada, yielding a BE of 27 µg of total ETU/L in urine associated with the Acceptable Daily Intake (ADI) and 6.7 µg/L associated with a 1e-6 cancer risk. These BEs are based on an analytical method that involves a digestion step to liberate conjugated ETU, thus producing 'total' ETU in urine. The BE values derived in this manuscript can serve as a guide to help public health officials and regulators interpret population based ETU biomonitoring data in a public health risk context.

Biomonitoring Equivalents for glyphosate.

One of the most widely used herbicides worldwide, glyphosate is registered for use in many agricultural and non-agricultural settings. Accordingly, regulatory authorities develop toxicology reference values (TRVs) to conduct risk assessments for potential exposures. Exposures to glyphosate are typically biomonitored via measures of glyphosate in urine. However, measured concentrations of glyphosate in urine, with units mg/L urine, cannot be directly interpreted using the available TRVs as they are presented in terms of daily intake levels (e.g. mg/kg-bw per day). In this evaluation, we review available health-based risk assessments and TRVs for glyphosate and derive Biomonitoring Equivalent (BE) values for interpretation of population biomonitoring data. Biomonitoring Equivalents (BEs) are defined as the concentration or range of concentrations of a chemical or its metabolite in a biological medium (blood, urine, human milk, etc.) that is consistent with an existing health-based TRVs such as a reference dose (RfD) or tolerable daily intake (TDI). The BE values derived in this manuscript are screening values that can help public health officials and regulators interpret glyphosate biomonitoring data.

A framework for screening sites at risk from contaminants of emerging concern.

Trace levels of a variety of currently unregulated organic chemicals have been detected in treated wastewater effluents and surface waters that receive treated effluents. Many of these chemicals of emerging concern (CECs) originate from pharmaceuticals and personal care products that are used widely and that frequently are transported "down the drain" to a wastewater treatment plant (WWTP). Actual effects of CECs on aquatic life have been difficult to document, although biological effects consistent with effects of some CECs have been noted. There is a critical need to find appropriate ways to screen wastewater sites that have the greatest potential of CEC risk to biota. Building on the work of several researchers, the authors present a screening framework, as well as examples based on the framework, designed to identify high-risk versus lower-risk sites that are influenced by WWTP effluent. It is hoped that this framework can help researchers, utilities, and the larger water resource community focus efforts toward improving CEC risk determinations and management of these risks.

Mercury(II) bioaccumulation and antioxidant physiology in four aquatic insects.

We examined Hg(II) bioaccumulation and compartmentalization patterns in conjunction with antioxidant responses in four aquatic insect species: two caddisflies (Chimarra sp. and Hydropsyche betteni) and two mayflies (Maccaffertium modestum and Isonychia sp). Total antioxidant capabilities differed among unexposed larvae, with both caddisfly species exhibiting elevated antioxidant activities relative to the mayflies. We were able to account for these differences by examining the constitutive activities of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), and superoxide dismutase (SOD), in the four species. We also examined levels of reduced and oxidized glutathione and cysteine in the insects. Glutathione peroxidase and SOD were the most responsive to Hg exposure, with GPx catalytic activity increasing between 50 and 310%. Superoxide dismutase activity decreased between 35 and 50%. This SOD suppression was shown to be dose-dependent in both caddisflies, butthe strength of this suppression did not appear to be related to rates of uptake. Surprisingly, little Hg (<10%) was found in the heat-stable cytosolic protein subcellular compartment in each of the four species, suggesting that Hg was not well detoxified. By combining bioaccumulation studies with other physiological measures, we can begin to better understand the consequences of trace metal pollutants in nature.

Changes in the timing of reproduction following chronic exposure to ibuprofen in Japanese medaka, Oryzias latipes.

Effluents from wastewater treatment plants and untreated sewage constitute a low concentration but continuous source of pharmaceutical products to the aquatic environment. One such drug, ibuprofen, is a non-steroidal anti-inflammatory agent that primarily acts through inhibition of cyclooxygenase (COX) activity. Oryzias latipes (Japanese medaka) were exposed for 6 weeks via water to three concentrations of ibuprofen (1-100 microg/L nominal concentrations) and a water control. Reproductive parameters, including frequency of spawning, fecundity, egg size, and rate of fertilization, were measured for each pair of adult medaka following 6 weeks of exposure. Livers homogenates from exposed individuals were assayed for COX activity and whole individuals were histologically examined for tissue damage. Increasing exposure to ibuprofen significantly increased the number of eggs per reproductive event, but decreased the number of spawning events per week. Liver tissue collected from females had less variability in COX activity with increasing concentration of ibuprofen exposure, and tended to have elevated hepatosomatic indices. No pathological damage was evident the in the gills, livers and head kidneys of animals from the highest exposure group. The results of this experiment begin to show that exposure to chronic low levels of ibuprofen alter the pattern of reproduction and may produce sex-specific responses in teleosts.