Development of Lead Source-specific Exposure Standards Based on Aggregate Exposure Assessment: Bayesian Inversion from Biomonitoring Information to Multipathway Exposure

Exposure of children to lead is of great concern, and the exposure standards for different media are important for protecting public safety. However, these media-specific standards often fail to ensure the safety of children even when environmental lead levels are lower than the quality standards since humans are often exposed to lead via multiple pathways. To establish exposure standards to protect children from hazards associated with exposure to lead, an analytical tool for assessing aggregate exposure to lead based on Bayesian hierarchical model was developed, and then was used to update the external lead exposure of diet, paint, soil, air and drinking water using the blood lead levels in Chinese children aged 1–6 years. On the basis of updated external exposure, the source allocations for diet, paint, soil, air, and drinking water in China were 65.80 ± 7.92%, 16.98 ± 7.88%, 13.65 ± 5.05%, 3.36 ± 1.75%, and 0.20 ± 0.14%, respectively. Based on the estimated source allocations, the exposure standards were evaluated to be 0.2 μg/m³, 24.25 mg/kg, 0.027 μg/L, 0.051 μg/mg, 0.042 μg/mg, 38.02 μg/mg for air, soil, water, grains, vegetables, and paint, respectively. Since the standards setting procedure was based on the multipathway aggregate exposure assessment of lead, the newly proposed exposure standards should ensure the safety of children

Distribution is a Major Factor Affecting Bioaccumulation of Decabrominated Diphenyl Ether: Chinese Sturgeon (<i>Acipenser sinensis</i>) as an Example

While decabromodiphenyl ether (BDE-209) has very low bioavailability and a rapid biotransformation rate, it exhibits high bioaccumulation in wildlife. To explore the bioaccumulation mechanism of BDE-209 in organisms, its toxicokinetic processes were investigated in Chinese sturgeons from the Yangtze River. Different from less brominated BDEs, lipids did not play an important role in the distribution of BDE-209 with relatively high concentrations detected in liver (54.5 ± 3.3 ng/g wet weight (ww)), gills (47.4 ± 2.9 ng/g ww), and intestine (41.9 ± 3.0 ng/g ww), followed by stomach (21.9 ± 9.0 ng/g ww), muscle (19.1 ± 5.6 ng/g ww), heart (7.5 ± 5.2 ng/g ww), gonad (6.8 ± 4.9 ng/g ww), adipose (4.9 ± 1.2 ng/g ww), and egg (2.8 ± 2.3 ng/g ww). In vitro metabolism of BDE-209 by microsomal fractions of Chinese sturgeon found that BDE-209 was biotransformed rapidly with the rate constant (<i>K</i>) of 0.039 h^–1 in liver. BDE-126, BDE-154, BDE-188, BDE-184, BDE-183, BDE-202, BDE-201, and BDE-204/197 were observed as debrominated products of BDE-209 after incubation, and their formation rates were 0.026, 0.016, and 0.006 h^–1 for BDE-126 BDE-184, and BDE-154, respectively. The concentration ratios between heart and intestine for individual PBDEs suggested slow delivery of BDE-209 among tissues after absorption. A Bayesian hierarchical model was further developed to estimate partition coefficients in a physiologically based pharmacokinetic model of BDE-209 in Chinese sturgeon. The estimated partition coefficients between tissues and blood were higher than those of less brominated BDE or PCBs in various animals, suggesting that the low partition ratios from blood to tissues would lead to high bioaccumulation of BDE-209, especially in absorbing organs

Occurrence and Source of Nitrosamines and Secondary Amines in Groundwater and its Adjacent Jialu River Basin, China

The presence of mutagenic and carcinogenic nitrosamines in groundwater is of great concern. In this study, eight nitrosamines including <i>N</i>-nitrosodimethylamine (NDMA), <i>N</i>-nitrosodiethylamine (NDEA), <i>N</i>-nitrosomethylethylamine (NMEA), <i>N</i>-nitrosopyrrolidine (NPYR), <i>N</i>-nitrosomorpholine (NMOR), <i>N</i>-nitrosopiperidine (NPIP), <i>N</i>-nitrosodi-n-propylamine (NDPA), and <i>N</i>-nitrosodi-n-butylamine (NDBA) and corresponding secondary amines were investigated in shallow groundwater, river water, and wastewater samples collected from the Jialu River basin. The total concentrations of nitrosamines and secondary amines in groundwater were ND–101.1 ng/L and 0.36–4.38 μg/L, respectively. NDMA and its secondary amine DMA (44.7%/40.1%) were the predominant compounds in groundwater, followed by NDEA/DEA (21.7%/29.3%) and NDBA/DBA (26.4%/27.4%). Relatively high concentrations of these six compounds were also observed in river water that was influenced by the direct discharge of industrial and domestic wastewater. Using acesulfame as a quantitative population marker, the contribution of domestic sources to the concentrations of nitrosamines and secondary amines was 39–85% in downstream reaches of the Jialu River, and that of industrial sources was estimated to be 65–98% in other sites of the area. Both on-site leakage of domestic and industrial wastewater and leaching from river water would contribute to the occurrence of target pollutants in groundwater. The target pollutants posed a cancer risk of 4.12 × 10^–5 to the local populations due to the direct usage of groundwater as potable water

Occurrences of Three Classes of Antibiotics in a Natural River Basin: Association with Antibiotic-Resistant <i>Escherichia coli</i>

To investigate the occurrence of antibiotics in urban rivers and their association with antibiotic-resistant Escherichia coli, 20 (fluoro)­quinolone antibiotics (FQs), 16 tetracycline antibiotics (TCs) and their degradation products, and 25 sulfonamides (SAs) and some degradation products were determined in 45 river samples and 13 discharged wastewater samples collected from Wenyu River and its tributaries and 4 composite effluent samples from sewage treatment plants in Beijing, China. Fifteen FQs, eight TCs, including four degradation chemicals, and sixteen SAs, including four acetylated products, were detected in the river water. The SAs were the dominant antibiotic (total concentrations up to 3164.0 ng/L) in river water, followed by FQs (1430.3 ng/L) and TCs (296.6 ng/L). The sum concentrations for each class of detected antibiotic in the 13 discharge site samples were higher than those in river samples, up to 12326.7 ng/L for SAs, 6589.2 ng/L for FQs, and 730.1 ng/L for TCs, largely contributing to the high concentrations in the river basin. Log–linear regression analysis confirmed that the concentrations of FQs, TCs, and SAs in the Wenyu River basin were strongly correlated with the number of E. coli resistant to FQs (<i>p</i> < 0.05), TCs (<i>p</i> < 0.05), and SAs (<i>p</i> < 0.05), providing evidence for the environmental impacts of antibiotic usage