Mengling Tang

Status, Influences and Risk Assessment of Hexachlorocyclohexanes in Agricultural Soils Across China

Large amounts of hexaclorocyclohexanes (HCHs) were historically applied to Chinese soils. However, there has been limited information on the residue patterns of HCHs in soils at a national scale in China. In this study, surface soil samples were collected from agricultural fields across China, and the concentrations of HCHs and enantiomeric fractions (EFs) of α-HCH were measured. The results showed that the average concentrations of α-HCH, β-HCH, γ-HCH, and total HCHs in Chinese agricultural soils were 0.190, 1.31, 0.236, and 1.74 ng g(-1), respectively. Residues of HCHs likely originated from past usage of technical HCHs. The isomers of α-HCH and γ-HCH tended to accumulate in the sites with lower total HCH concentrations, lower temperature, higher elevation, and less wet precipitation when compared to β-HCH. Enantiomeric analysis showed a preferential degradation of (-)-α-HCH. Human health risks via various exposure routes to HCHs in soils were further estimated. Overall, the mean hazard index (HI) linked to noncarcinogenic risks was below 1, suggesting an absence of noncarcinogenic risks of HCHs in Chinese soils. In addition, the cancer risk values were all below 10(-4), which indicates low or very low risks.

Exposure to organochlorine pollutants and type 2 diabetes: a systematic review and meta-analysis.

Objective Though exposure to organochlorine pollutants (OCPs) is considered a risk factor for type 2 diabetes (T2DM), epidemiological evidence for the association remains controversial. A systematic review and meta-analysis was applied to quantitatively evaluate the association between exposure to OCPs and incidence of T2DM and pool the inconsistent evidence. Design and Methods Publications in English were searched in MEDLINE and WEB OF SCIENCE databases and related reference lists up to August 2013. Quantitative estimates and information regarding study characteristics were extracted from 23 original studies. Quality assessments of external validity, bias, exposure measurement and confounding were performed, and subgroup analyses were conducted to examine the heterogeneity sources. Results We retrieved 23 eligible articles to conduct this meta-analysis. OR (odds ratio) or RR (risk ratio) estimates in each subgroup were discussed, and the strong associations were observed in PCB-153 (OR, 1.52; 95% CI, 1.19–1.94), PCBs (OR, 2.14; 95% CI, 1.53–2.99), and p,p′-DDE (OR, 1.33; 95% CI, 1.15–1.54) based on a random-effects model. Conclusions This meta-analysis provides quantitative evidence supporting the conclusion that exposure to organochlorine pollutants is associated with an increased risk of incidence of T2DM.

Effect of weathering treatment on the fractionation and leaching behavior of copper in municipal solid waste incinerator bottom ash

This work describes the effect of weathering of fresh quenched municipal solid waste incinerator (MSWI) bottom ash on the fractionation and leaching behavior of Cu. A sequential extraction procedure was used to characterize the fractionation of Cu in the fresh and weathered MSWI bottom ash samples. It showed that the organic matter bound fraction of Cu decreased drastically from 69% to 37% during the weathering treatment, while the residual fraction, Fe-Mn oxides bound fraction, carbonate bound fraction and exchangeable fraction increased from 24% to 54%, 3% to 4%, 2% to 3% and 2% to 3%, respectively. Furthermore, two standard leaching procedures, synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP), were carried out on the fresh and weathered samples. The leaching of Cu was attenuated with the process of weathering treatment in the SPLP procedure, but was enhanced in the TCLP procedure. The results suggested that the weathering treatment could change the fractionation and leaching behavior of Cu in MSWI bottom ash. Further research is required to correlate weathering of ash and mobility of Cu.

Lead, mercury, and cadmium in umbilical cord serum and birth outcomes in Chinese fish consumers.

Heavy metals such as lead (Pb), mercury (Hg), and cadmium (Cd) were detected in the islands of Yangtze River estuary and Hangzhou bay and their exposure caused potential health risk for the residents. To assess the exposure levels of Pb, Hg, and Cd, the umbilical cord serum samples were collected from 103 mother-newborn pairs as the noninvasive specimens. The association of the concentration of Pb, Hg, and Cd with the birth outcomes was evaluated. Pb, Hg, and Cd had high exposure levels with the median concentrations at 76.20 μg L(-1) [interquartile range (IQR): 44.71, 115.80], 21.94 μg L(-1) (IQR: 15.10, 27.64), and 6.36 μg L(-1) (IQR: 3.63, 13.34), respectively. A unit increase in the Pb umbilical cord serum concentration (μg L(-1)) was significantly associated with a 0.29 cm (95% CI: -0.50, -0.09) decrease in birth height and a 0.22 cm (95%CI: -0.44, 0.00) decrease in head circumference. The middle tertile Pb and Hg exposure levels were found significantly negative effects on birth outcomes compared with low tertile exposure levels. Exposure to Cd showed no apparent effect on birth outcomes. Our results suggested that Pb and Hg exposure has potential adverse effects on birth outcomes in Chinese fish consumers from Yangtze River outlet and Hangzhou bay estuary regions.

Evaluation of site-specific lateral inclusion zone for vapor intrusion based on an analytical approach

In 2002, U.S. EPA proposed a general buffer zone of approximately 100 feet (30 m) laterally to determine which buildings to include in vapor intrusion (VI) investigations. However, this screening distance can be threatened by factors such as extensive surface pavements. Under such circumstances, EPA recommended investigating soil vapor migration distance on a site-specific basis. To serve this purpose, we present an analytical model (AAMLPH) as an alternative to estimate lateral VI screening distances at chlorinated compound-contaminated sites. Based on a previously introduced model (AAML), AAMLPH is developed by considering the effects of impervious surface cover and soil geology heterogeneities, providing predictions consistent with the three-dimensional (3-D) numerical simulated results. By employing risk-based and contribution-based screening levels of subslab concentrations (50 and 500 μg/m(3), respectively) and source-to-subslab attenuation factor (0.001 and 0.01, respectively), AAMLPH suggests that buildings greater than 30 m from a plume boundary can still be affected by VI in the presence of any two of the three factors, which are high source vapor concentration, shallow source and significant surface cover. This finding justifies the concern that EPA has expressed about the application of the 30 m lateral separation distance in the presence of physical barriers (e.g., asphalt covers or ice) at the ground surface.

Potential application of biocover soils to landfills for mitigating toluene emission

Biocover soils have been demonstrated to be a good alternative cover material to mitigate CH4 emission from landfills. To evaluate the potential of biocover soil in mitigating emissions of non-methane volatile organic compounds (NMVOCs) from landfills, simulated cover soil columns with the influx of toluene (chosen as typical of NMVOCs) concentrations of 102-1336 mg m(-3) in the presence or absence of the major landfill gas components (i.e., CH4 and CO2) were conducted in this study. In the two experimental materials (waste biocover soils (WBS) and landfill cover soils (LCS)), higher toluene reduction was observed in WBS with respect to LCS. After the introduction of landfill gas, an increase of microbial diversity and relative abundance of toluene-degrading bacteria and methanotrophs occurred in WBS. To illustrate the role of toluene-degrading activity in mitigating toluene emissions through landfill covers, an analytical model was developed by incorporating the steady-state vapor transport with the first-order kinetics of aerobic biodegradation limited by O2 availability. This study demonstrated that biocover soils have great potential in applying to landfills for mitigating toluene emission to the atmosphere.

Toxic effects of trace elements on newborns and their birth outcomes.

Some trace elements are essential for newborns, their deficiency may cause abnormal biological functions, whereas excessive intakes due to environmental contamination may create adverse health effects. This study was conducted to measure the levels of selected trace elements in Chinese fish consumers by assessing their essentiality and toxicity via colostrum intake in newborns, and evaluated the effects of these trace elements on birth outcomes. Trace elements in umbilical cord serum and colostrum of the studied population were relatively high compared with other populations. The geometric means (GM) of estimated daily intake (EDI, mgday(-1)) of the trace elements were in the safe ranges for infant Dietary Reference Intakes (DRIs) recommended by the United States Food and Drug Administration (FDA). When using total dietary intake (TDI, mgkg(-1)bwday(-1)), zinc (Zn) (0.880mgkg(-1)bwday(-1)) and selenium (Se) (6.39×10(-3)mgkg(-1)bwday(-1)) were above the Reference Doses (RfD), set by the United States Environmental Protection Agency (EPA). Multivariable linear regression analyses showed that Se was negatively correlated with birth outcomes. Our findings suggested that overloading of trace elements due to environmental contamination may contribute to negative birth outcomes.

Investigating the Role of Soil Texture in Vapor Intrusion from Groundwater Sources

Soil texture is believed to play a significant role in the migration of subsurface volatile chemicals into buildings at contaminated sites, an exposure process known as vapor intrusion (VI). In this study, we investigated the role of soil texture in determining the attenuation of contaminant soil gas concentration from groundwater source to receptor building. We performed soil column experiments, numerical simulations, and statistical analysis of the USEPAs VI database. The soil column experiments were conducted with commercial sand and soils with sand and sandy loam textures. Measured one-dimensional soil gas concentration profiles were compared with numerical predictions. Good agreement between experiments and model results supports the use of the classical multiphase chemical transport equation for simulating contaminant vapor transport from groundwater through the vadose zone. A full three-dimensional numerical model was then used to simulate typical VI scenarios with groundwater sources. Results indicate that, although soil particle texture can play a role in determining subslab-to-indoor air concentration attenuation, there is no obvious relationship between soil particle size and groundwater source-to-subslab except in the case of a shallow contaminant source. This conclusion is consistent with results reported in USEPAs VI database, in which variation in soil particle size does not affect source-to-subslab attenuation factors but does influence subslab-to-indoor air concentration attenuation factors by an average of about 0.4 order of magnitude. This finding suggests that an appropriate focus of VI site investigation should include the shallow soil beneath the building foundation.

Enantioselective Activity and Toxicity of Chiral Herbicides

Chirality is a natural property that is well known to chemists and has been generally recognized in the life sciences since Pasteur discovered the optical isomers of tartrate and van’t Hoff and LeBel proposed the theory of the stereostructure of carbon compounds (GassmannKuo & Zare, 1985; Koeller & Wong, 2001; KondruWipf & Beratan, 1998). Almost all of the biological macromolecules, such as DNA, RNA, protein, polynucleotides, and even the amino acids, the basic structural units of life, are chiral(Roelfes, 2007). Although the enantiomers of chiral substances have the same physicochemical properties, their biochemical activities, unlike abiotic transformations, can be quite different because biochemical processes usually show high stereoor enantioselectivity (Muller & Kohler, 2004). For instance, enantioselective reactions occur in biological enrichment(Hegeman & Laane, 2002), degradation and other physiological actions(Wong, 2006). For organisms, enantiomers often exhibit different effects or toxicities. The “active” enantiomer of a chiral chemical may have the desired effect on a target species, whereas the other enantiomer may not(Garrison, 2006). It is advisable to use only the biologically active enantiomers, thereby reducing the total amount of chemical pollutants released into the environment.

The development of the social health scale for the elderly

BackgroundWith the elderly population comprising an increasing large proportion of society, a valid and reliable measure of social health in the elderly is indispensable for a comprehensive health assessment. The objective of this study is to develop a Social Health Scale for the Elderly (SHSE).MethodsA draft scale was generated based on a literature review and expert surveys. Pilot testing was conducted from December 14, 2015, to January 8, 2016. Some items were removed after assessment with five statistical analysis methods. Field testing began on November 6, 2016, and ended on January 20, 2017. After field testing, the reliability and validity of the scale were assessed and the norms in Hangzhou were calculated.ResultsIn the two tests, 430 and 2404 subjects were included in the statistical analyses. The long form of the SHSE (SHSE-L) contained 25 items, 14 of which were also in the short form (SHSE-S). The internal consistency of the SHSE-L was acceptable. The test-rest reliability and inter-rater reliability were moderate, but the concurrent validity, construct validity, and convergent and discriminant validity were desirable in both versions. The standard and percentile rank norms in Hangzhou, China were developed based on the field testing data.ConclusionsThe population-based social health of the Chinese elderly can be validly and reliably assessed with the SHSE.