Biomarkers of internal dose for the assessment of environmental exposure to benzene

The urinary excretion of t,t-muconic acid (t,t-MA), S-phenylmercapturic acid (SPMA) and urinary benzene and the influence of a smoking habit and of exposure to urban traffic on the urinary excretion of these biomarkers were investigated in 137 male adults from the general population. All subjects were not occupationally exposed to benzene and resident in two cities in Puglia (Southern-Italy). Environmental exposure to benzene was measured using passive personal samplers. The biomarkers t,t-MA, SPMA and urinary benzene were determined in urine samples collected from each subject at the end of the environmental sampling. The percentage of cases above the limit of detection was higher for SPMA and urinary benzene in smokers than in non-smokers, and for airborne benzene and urinary benzene in subjects exposed to urban traffic. Airborne benzene was correlated with the time spent in urban traffic during the environmental sampling. Among the biomarkers, urinary benzene was found to be correlated with airborne benzene only in non-smokers, and with the time spent in urban traffic, both in smokers and non-smokers considered together, and in non-smokers only. Finally, multiple regression analysis showed that the urinary excretion of all the biomarkers was dependent on the number of cigarettes smoked per day and, for urinary benzene, also on the time spent in urban traffic. In conclusion, urinary benzene seems to be a more valid biomarker than t,t-MA and SPMA to assess environmental exposure to extremely low concentrations of benzene. Cigarette smoking prevailed over traffic exhaust fumes in determining the internal dose of benzene.     

Distribution of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, dioxin-like polychlorinated biphenyl and polycyclic aromatic hydrocarbons in the sediment of Temsah lake, Suez Canal, Egypt

Lake Temsah is one of the main wetlands in the Suez Canal region, and the main source for fish for the area. The lake is the end-point of several wastewater effluents. In the present study, residues of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbons (PAH) were monitored in the sediment of the lake. Samples were collected from six different sampling stations around the lake using a box-corer sampler, then kept frozen. Samples were extracted and cleaned up before residue determination was conducted using an HRGC/HRMS. An HP 6890 plus gas chromatograph was coupled to a Micromass Autospec Ultima mass spectrometer operating in EI mode at 35 eV and with a resolution of 10.000 (5% valley). PCDDs and PCDFs were detected in all sediment samples collected from various sampling stations. Results showed some progressive increase in PCDDs concentrations relevant to increase in chlorination. In the PCDD group of congeners, 1, 2, 3, 4, 6, 7, 8, 9 octa-CDD had the highest detected concentrations in all samples, while 2, 3, 7, 8 tetra-CDD showed the lowest concentrations. The World Health Organization toxicity equivalents ranged from 0.387 to 11.20 ng kg^-1 d.w. For PCDD homologues, hexa-CDD was the most dominant homologue in all sediment samples analysed. Regarding dioxin-like PCBs, results showed that IUPAC No. 118 congener, 2, 3, 4, 4, 5, pentachlorobiphenyl was the most concentrated of all detected congeners, with concentrations ranging between 0.039 and 43.201 µg kg^-1. For polycyclic aromatic hydrocarbons, benzo(b+k+j)fluoranthene had the highest concentrations in almost all sampling stations. However, fluorene was the smallest detected concentration in almost all stations. This result would indicate that PAH contamination of the lake seems to be coming from one main source in all sampling stations. The present work is the first record of PCCDs, PCCFs, and dioxin-like PCBs in the Temsah lake. The concentrations of the contaminants monitored in this study, especially those of PAHs, are rather alarming. Efforts should be made to stop point sources that contaminate the lake.     

Dimethyl disulfide and dimethyl trisulfide: so similar yet so different in evoking biological responses in saprophilous flies

Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) are used by saprophilous insects to locate breeding sites (decaying organic matter), and by brood-site deceptive flowers to attract such insects. However, little is known about the relative importance of these two compounds in eliciting electrophysiological and behavioral responses in the insects. Here, we compared the relative attractiveness of DMDS and DMTS to saprophilous flies in field choice experiments and tested whether potential differences in field responses can be explained by differences in electrophysiological antennal responses to these compounds. Field experiments revealed that the attractiveness of a mixture of these compounds is due to DMTS alone. This result was confirmed by electroantennographic recordings in which flies of four tested species of Calliphoridae (Lucilia sericata, L. caesar, Calliphora vicina, Protocalliphora azurea) and one Muscidae (Musca domestica) respond clearly to DMTS, but not to DMDS. In house flies, however, DMTS elicited electrophysiological responses only, not reflected in behavioral assays. Despite the fact that DMTS and DMDS exhibit similar chemical structures, both the electroantennographic and field responses from saprophilous flies to these two compounds strongly differed. Our study suggests that oligosulfide-responsive saprophilous flies rely on DMTS and not DMDS for finding appropriate breeding sites and that DMTS and not DMDS could act as a key mediator for pollinator attraction in brood-site deceptive plants.     

Effects of female mating status on copulation behaviour and sperm expenditure in the freshwater crayfish <Emphasis Type="Italic">Austropotamobius italicus</Emphasis>

Sperm competition models predict that males should adjust their sperm expenditure according to the risk and/or intensity of sperm competition. In this paper, we analysed copulatory behaviour of both sexes and sperm expenditure in relation to female mating status (virgin or mated) in the freshwater crayfish Austropotamobius italicus, a species where males have been reported to feed on and remove sperm laid by other males. The same females were allowed to be inseminated sequentially by two males, and we compared the sexual behaviours of partners between the first (virgin females) and the second mating (mated females). We found that female resistance did not differ between the first and the second mating, nor males refused or took more time to mount a mated female. However, when mating with a mated female, males reached an effective copulation position significantly later. This occurred because second-mating males removed, by eating, all or most spermatophores previously deposited by first males. As removal was often incomplete, this resulted in a larger amount of sperm being deposited on female ventral parts after the second mating, although second males did not allocate more sperm to mated females than first males did. Thus, the peculiar mode of sperm competition, where males remove previously deposited sperm, and the consequent predictable strong last male prevalence in paternity likely led to the observed lack of adjustment of sperm expenditure to female mating status in this species.     

Assessment of reference values for polychlorinated biphenyl concentration in human blood

A chemical factory which produced polychlorinated biphenyls (PCBs) operated in Brescia, North Italy, (about 200000 inhabitants) from the 1930s to the 1980s. High levels of PCBs were recently found in soil, food and people living in an area close to the factory. We performed a survey among the general population living in non-polluted areas of the town in order to define the reference values (RVs) of the non-exposed population. A random sample of subjects aged 20-79 years (50% males) was selected. Participants underwent PCB determination and were interviewed on their residential and occupational history and current diet. For RV determination, subjects who had resided in the polluted area or consumed any food produced in the area in their lifetime were excluded. Eight hundred and ninety-two subjects were contacted, 579 (65%) of whom agreed to participate; 311 of them were considered for RV determination (53% male, mean age=48.7 years). Total PCB serum levels, computed as the sum of the 24 congeners determined, were: mean=5.15ng/ml (SD=8.83), median=4.11ng/ml, range=0.4-34.12ng/ml, 95th centile=14.38ng/ml. Lipid-adjusted mean and median were 897 and 705ng/g lipid, respectively. PCB values showed positive correlations with age (Spearman's r=0.76) and with serum concentration of total cholesterol (r=0.40) and triglycerides (r=0.36). No association was found with gender, cigarette smoking, alcohol or diet. Seven PCB congeners, (PCB 180, 153, 138, 170, 194, 118, and 156), including those at higher chlorination, were present in more than 30% of the subjects and contributed 99% of the total PCB levels, with a modest role of dioxin-like congeners.     

Present to future sediment transport of the Brahmaputra River: reducing uncertainty in predictions and management

The Brahmaputra River in South Asia carries one of the world’s highest sediment loads, and the sediment transport dynamics strongly affect the region’s ecology and agriculture. However, present understanding of sediment conditions and dynamics is hindered by limited access to hydrological and geomorphological data, which impacts predictive models needed in management. We here synthesize reported peer-reviewed data relevant to sediment transport and perform a sensitivity analysis to identify sensitive and uncertain parameters, using the one-dimensional model HEC-RAS, considering both present and future climatic conditions. Results showed that there is considerable uncertainty in openly available estimates (260–720 Mt yr^?1) of the annual sediment load for the Brahmaputra River at its downstream Bahadurabad gauging station (Bangladesh). This may aggravate scientific impact studies of planned power plant and reservoir construction in the region, as well as more general effects of ongoing land use change and climate change. We found that data scarcity on sediment grain size distribution, water discharge, and Manning’s roughness coefficient had the strongest controls on the modelled sediment load. However, despite uncertainty in absolute loads, we showed that predicted relative changes, including a future increase in sediment load by about 40 % at Bahadurabad by 2075–2100, were consistent across multiple model simulations. Nevertheless, for the future scenarios we found that parameter uncertainty almost doubled for water discharge and river geometry, highlighting that improved information on these parameters could greatly advance the abilities to predict and manage current and future sediment dynamics in the Brahmaputra river basin.     

Exposure to polychlorinated biphenyls in residents near a chemical factory in Italy: the food chain as main source of contamination

High levels of PCBs were recently found in soil, food and some farmers living close to a chemical factory which until the 1980s had produced polychlorinated biphenyls (PCBs) in Brescia, North Italy. We performed a survey on a random sample of subjects aged 20-79 years living in various areas of the town with different levels of soil pollution to investigate factors associated with increased levels of PCB in serum (24 congeners were tested). Total PCB values were closely related to age (Spearman r=0.68; p<0.0001). The 166 consumers of locally produced food had higher PCB levels than non-consumers (median=1143 versus 719; 95th centile=9301 versus 2635ng/g lipid) with the highest levels among consumers of food produced in the most contaminated area close to the factory (median=2551; 95th centile=33464ng/g lipid). A dose-effect relationship between consumption of food produced in this area and PCB blood levels was observed (Spearman r=0.52, p=0.0014). Consumers of only plant food produced in this area had higher levels of PCB than non-consumers (median=1100; 95th centile=10,800ng/g lipid). Three subjects who had worked at the factory in the past showed high PCB levels. Distribution of PCB congeners did not differ between consumers of locally produced food and non-consumers, apart from PCB 209 which was found at high levels in former factory workers and was more common among consumers of food produced in the polluted area. In conclusion, we found high serum PCB levels in humans living in a highly polluted area in an industrialized town in Italy, due mainly to consumption of food produced in polluted areas.     

Reliability of groundwater vulnerability maps obtained through statistical methods

Statistical methods are widely used in environmental studies to evaluate natural hazards. Within groundwater vulnerability in particular, statistical methods are used to support decisions about environmental planning and management. The production of vulnerability maps obtained by statistical methods can greatly help decision making. One of the key points in all of these studies is the validation of the model outputs, which is performed through the application of various techniques to analyze the quality and reliability of the final results and to evaluate the model having the best performance. In this study, a groundwater vulnerability assessment to nitrate contamination was performed for the shallow aquifer located in the Province of Milan (Italy). The Weights of Evidence modeling technique was used to generate six model outputs, each one with a different number of input predictive factors. Considering that a vulnerability map is meaningful and useful only if it represents the study area through a limited number of classes with different degrees of vulnerability, the spatial agreement of different reclassified maps has been evaluated through the kappa statistics and a series of validation procedures has been proposed and applied to evaluate the reliability of the reclassified maps. Results show that performance is not directly related to the number of input predictor factors and that is possible to identify, among apparently similar maps, those best representing groundwater vulnerability in the study area. Thus, vulnerability maps generated using statistical modeling techniques have to be carefully handled before they are disseminated. Indeed, the results may appear to be excellent and final maps may perform quite well when, in fact, the depicted spatial distribution of vulnerability is greatly different from the actual one. For this reason, it is necessary to carefully evaluate the obtained results using multiple statistical techniques that are capable of providing quantitative insight into the analysis of the results. This evaluation should be done at least to reduce the questionability of the results and so to limit the number of potential choices.