Fetal methylmercury exposure as measured by cord blood mercury concentrations in a mother-infant cohort in Hong Kong

This study was designed to examine newborn infants in Hong Kong prenatally exposed to levels of methylmercury considered to increase risk of neurotoxic effects and to examine subject characteristics that modify the degree of prenatal mercury exposure. Mercury concentrations in 1057 sets of maternal and cord blood samples and 96 randomly selected maternal hair samples were measured. Subject characteristics were measured or collected by questionnaire. Of the 1057 cord blood samples collected only 21.6% had mercury concentrations less than 29 nmol/L (5.8 micro g/L). Median maternal hair mercury concentration was 1.7 ppm. The geometric mean cord to maternal blood mercury ratio was 1.79 to 1. Increasing maternal fish consumption and maternal age were found to be associated with increased cord blood mercury concentrations. Marine fish consumption increased cord blood mercury concentrations more than freshwater fish (5.09%/kg vs 2.86%/kg). Female babies, maternal alcohol consumption and increasing maternal height were associated with decreased cord blood mercury concentrations. Pregnant women in Hong Kong consume large amounts of fish and as a result, most of their offspring have been prenatally exposed to moderately high levels of mercury. In this population, pregnant women should choose freshwater over marine fish and limit fish consumption.     

Task knowledge overlap and knowledge variety: the role of advice network structures and impact on group effectiveness

Drawing from the structural perspective of social capital theory, this research investigates how internal and external advice network structures influence knowledge overlap and variety and, how these knowledge dimensions in turn influence group effectiveness. Findings from two studies on knowledge‐intensive groups indicate that different advice network structures are associated with knowledge overlap and knowledge variety, and only knowledge variety was significantly associated with group effectiveness. In addition, despite implicit understanding that advice networks aid performance through enhancing knowledge outcomes, only knowledge variety was found to mediate the relationship between external network and group effectiveness. Implications for theory and practice are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Electronic waste management approaches: An overview

Electronic waste (e-waste) is one of the fastest-growing pollution problems worldwide given the presence if a variety of toxic substances which can contaminate the environment and threaten human health, if disposal protocols are not meticulously managed. This paper presents an overview of toxic substances present in e-waste, their potential environmental and human health impacts together with management strategies currently being used in certain countries. Several tools including Life Cycle Assessment (LCA), Material Flow Analysis (MFA), Multi Criteria Analysis (MCA) and Extended Producer Responsibility (EPR) have been developed to manage e-wastes especially in developed countries. The key to success in terms of e-waste management is to develop eco-design devices, properly collect e-waste, recover and recycle material by safe methods, dispose of e-waste by suitable techniques, forbid the transfer of used electronic devices to developing countries, and raise awareness of the impact of e-waste. No single tool is adequate but together they can complement each other to solve this issue. A national scheme such as EPR is a good policy in solving the growing e-waste problems.     

Impact of Construction Waste Disposal Charging Scheme on work practices at construction sites in Hong Kong

Waste management in the building industry in Hong Kong has become an important environmental issue. Particularly, an increasing amount of construction and demolition (C&D) waste is being disposed at landfill sites. In order to reduce waste generation and encourage reuse and recycling, the Hong Kong Government has implemented the Construction Waste Disposal Charging Scheme (CWDCS) to levy charges on C&D waste disposal to landfills. In order to provide information on the changes in reducing waste generation practice among construction participants in various work trades, a study was conducted after 3 years of implementation of the CWDCS via a structured questionnaire survey in the building industry in Hong Kong. The study result has revealed changes with work flows of the major trades as well as differentiating the levels of waste reduced. Three building projects in the public and private sectors were selected as case studies to demonstrate the changes in work flows and the reduction of waste achieved. The research findings reveal that a significant reduction of construction waste was achieved at the first 3 years (2006–2008) of CWDCS implementation. However, the reduction cannot be sustained. The major trades have been influenced to a certain extent by the implementation of the CWDCS. Slight improvement in waste management practices was observed, but reduction of construction waste in the wet-finishing and dry-finishing trades has undergone little improvement. Implementation of the CWDCS has not yet motivated subcontractors to change their methods of construction so as to reduce C&D waste.     

Stability of the conjugated species of environmental phenols and parabens in human serum

In humans, the metabolism of environmental phenols may include the formation of conjugated species (e.g., glucuronides and sulfates), but the free species—not the conjugated forms—are considered biologically active. Therefore, information on the concentration of these free species in blood or urine could be helpful for risk assessment. Because conjugates could hydrolyze to their corresponding free forms during collection, handling, and storage of biological specimens, information on the temporal stability of the conjugates is of interest. Previously, we reported the temporal stability of urinary conjugates of several environmental phenols, but data on the stability of phenols' conjugated species in serum, albeit critical if concentrations of free and conjugated species are compared, are largely unknown. In the present study, we investigate the stability of the conjugates of four phenols—bisphenol A, benzophenone-3, triclosan, and 2,5-dichlorophenol—and two parabens—methyl paraben and propyl paraben—in 16 human serum samples for 30 days at above-freezing temperature storage conditions (4 °C, room temperature, and 37 °C). These conditions reflect the worst-case scenarios that could occur during the short-term storage of biological samples before their long-term storage at controlled subfreezing temperatures. We found that the percentage of the conjugated species of the four detected compounds (2,5-dichlorophenol, triclosan, and methyl and propyl parabens) in these serum specimens even when stored at 37 °C for at least 30 days did not vary significantly. These preliminary data suggest that the phenols' serum conjugates appear to be more stable than their corresponding urinary conjugates, some of which started to hydrolyze within 24 h under similar storage conditions. The reported stability of these conjugated species in human serum also suggests that the free species are unlikely to have resulted from the hydrolysis of their corresponding conjugates. This information could be important for interpreting the low concentrations of free phenol species detected in serum samples of nonoccupationally exposed populations. To our knowledge, this is the first study to report on the stability of conjugated species in serum, and as such requires replication.     

Mutagenicity, genotoxicity and carcinogenic risk assessment of indoor dust from three major cities around the Pearl River Delta

The mutagenicity and genotoxicity of workplace dust including commercial office, secondary school, shopping mall, hospital, electronics factory and manufacturing plant in Hong Kong and settled house dust from Hong Kong, Shenzhen and Guangzhou were measured. Results indicated that indoor dust contained both frameshift and base pair substitution mutagens. Dust from manufacturing plant showed highest mutagenic potency on TA98±S9 and TA100±S9 activation, whereas, electronics factory showed highest genotoxicity with and without S9 activation. TA100 (-S9) mutagenic potency was significantly correlated with genotoxicity expressed as SOSIP (-S9) of workplace dust (r(2)=0.37, p<0.01). The total PAHs concentration of settled house dust from PRD ranged from 1.63 to 29.2μg/g. Linear regression analyses indicated that the PAHs likely accounted for about 45% of the TA98 with S9 mutagenic activity of workplace dust. TA98 (-S9) mutagenicity (r(2)=0.27, p<0.05) and SOSIP (-S9) of house dust (r(2)=0.41, p<0.01) were both significantly correlated with the number of inhabitants in the house. To achieve a more accurate cancer risk assessment, the oral bioaccessibility of B(a)A, Chry, B(b+k)F, B(a)P, D(ah)A and I(cd)P in different dust ranging from 1.3% to 17% was taken into account. Risk assessments indicated that about 26% of house dust samples resulted in unacceptable cancer risk (>1×10(-6)) for preschool children.     

Assessment of typical pollutants in waterborne by combining active biomonitoring and integrated biomarkers response

Organic pollutants, heavy metals and pharmaceuticals are continuously dispersed into the environment and have become a relevant environmental emerging concern. In this study, a situ assay to assess ecotoxicity of mixed pollutants was carried out in three typical sites with different priority contaminations in Guangzhou, China. Chemical analysis of organic pollutants, metals and quinolones in three exposure sites were determined by GC-ECD/MS, ICP-AES and HPLC, as well as, a combination of biomarkers including: ethoxyresorufin O-deethylase (EROD); aminopyrine N-demethylase (APND); erythromycin N-demethylase (ERND); glutathione S-transferase (GST); malondialdehyde (MDA); CYP1A; and P-glycoprotein (P-gp) mRNA expressions were evaluated in Mugilogobius abei. Results of chemical analysis in sediment samples revealed that the dominant chemicals were organic pollutants and heavy metals in Huadi River while quinolones in the pond. Bioassays indicated that differences among sites were in relation to some specific biomarkers. EROD and GST activities significantly increased after 72 h in situ exposure, but no difference was observed among the exposure sites. APND, ERND and MDA exhibited dissimilar change patterns for different priority pollutants. CYP1A and P-gp mRNA expressions were significantly induced at all exposure sites, whilst P-gp activity was typical for S2 with the highest levels of quinolones. The molecular biomarkers seemed to be more susceptible than enzyme activities. These assays confirmed the usefulness of applying a large array of various combined biomarkers at different levels, in assessing the toxic effects of mixed pollutants in a natural aquatic environment.     

Influence of nocturnal vertical stability on daytime chemistry: A one-dimensional model study

Nocturnal chemistry can play an important role in determining the initial morning conditions for daytime chemistry in urban areas. However, the impact on daytime O₃ levels is difficult to assess as the suppression of vertical trace gas transport leads to highly altitude dependent nocturnal chemistry, in particular with respect to the removal and conversion of nitrogen oxides (NO_x) and volatile organic compounds (VOC). One-dimensional (1-D) chemical transport model calculations for different nighttime vertical stabilities and different ozone formation regimes (i.e. NO_x- vs. VOC-sensitive) were performed assuming a 1000 m high daytime boundary layer and a growing nocturnal boundary layer reaching 200 m height at the end of the night. Exclusion of NO₃ chemistry from the model leads to daytime O₃ concentration changes from ?4% to +16% for different O₃ sensitivities. In all cases strong nocturnal vertical concentration profiles of NO_x, O₃, NO₃ and N₂O₅ and a dependence of these profiles on vertical stability were found at night. The nocturnal NO_x loss averaged over the lowest 1000 m changes by 9–24% for different vertical stabilities and ozone sensitivities. The impact of nocturnal vertical stability leads to 7–12% difference in O₃ concentration in the morning and ～0–2.5% in the afternoon.