Assessment of uranium concentration in the drinking water and associated health risks in Eastern Haryana,India

Quantification of uranium in drinking water has great significance considering its effects on human health. Drinking water samples collected from different sources, viz., hand pumps, tube-wells, and public water supply from Sonipat and Panipat districts of Haryana, India have been analyzed for uranium and other physico-chemical parameters. Uranium concentration in water samples was measured using Pulsed LED Fluorimeter. Uranium concentration in collected water samples ranges from 9.1 to 155.1 µg/L in Sonipat district and 14.9 to 123.3 µg/L in Panipat district. It was inferred from the data that uranium concentration in some water samples was higher than WHO &; USEPA recommended limit of 30 µg/L. The mean cancer risk due to uranium in drinking water in Sonipat and Panipat districts was found to be 1.40 × 10^?4 and 1.63 × 10^?4, respectively, which is lower than the maximum permissible limit (<10^?3). Total Dissolve Salts (TDS) in water samples of some villages in Sonipat district was higher than permissible limits for drinking prescribed by WHO &; BIS.     

Implications of Using Steady-State Conditions in Estimating Dermal Uptake of Volatile Compounds in Municipal Drinking Water: An Example of THMs

Dermal exposure to volatile compounds (VC) in municipal water while showering is typically estimated using a steady-state condition between VC in water impacting on skin and skin exposed to water. The lag times to achieve steady-state between VC and skin can vary in the range of 7.5–218.3 min, while shower duration is often less than these values. Estimates of dermal exposure to VC using steady-state while showering may misinterpret exposure. This study developed models and estimated exposure to some disinfection byproducts (DBPs) through dermal pathway by considering lag times while showering. Dermal uptakes of VC were compared using different approaches. In the proposed approach, uptakes of trihalomethanes were estimated between 9.55 × 10^?10–1.43 × 10^?8 mg/cm² of skin during the lag times from exposure to water with trihalomethanes of 50 μg/L. These values were higher than the steady-state estimates (1.37 × 10^?10–4.34 × 10^?9 mg/cm²), and lower than the average exposure analysis (4.12 × 10^-8–1.93 × 10^?6 mg/cm²). Using the Drinking Water Surveillance Program data in Ontario, chronic daily intakes of trihalomethanes were estimated to be 9.40 × 10^?7 (1.85 × 10^?7–1.65 × 10^?6), 3.89 × 10^?6 (7.11 × 10^?7–2.33 × 10^?5), and 1.40 × 10^?6 (4.0 × 10^?7–1.77 × 10^?6) mg/kg/day in Toronto, Ottawa, and Hamilton, respectively. The findings can be useful in understanding THMs exposure and risk through dermal pathway.     

A quantitative risk ranking model to evaluate emerging organic contaminants in biosolid amended land and potential transport to drinking water

A quantitative risk ranking model was developed for human exposure to emerging contaminants (EC) following treated municipal sewage sludge (“biosolids”) application to Irish agricultural land. The model encompasses the predicted environmental concentration (PEC) in soil, surface runoff, groundwater, and subsequent drinking water ingestion by humans. Human exposure and subsequent risk was estimated for 16 organic contaminants using a Monte Carlo simulation approach. Nonylphenols ranked the highest across three environmental compartments: concentration in soil (PEC_soil), runoff (PEC_runoff), and groundwater (PEC_groundwater), which had mean values of 5.69 mg/kg, 1.15 × 10^?2 µg/l, and 2.22 × 10^?1 µg/l, respectively. Human health risk was estimated using the LC₅₀ (chemical intake toxicity ratio, (RR)) as a toxicity endpoint combined with PEC_runoff and PEC_groundwater. NP ranked highest for LC₅₀ combined with PEC_runoff and PEC_groundwater (mean RR values 1.10 × 10^?4 and 2.40 × 10^?3, respectively). The model highlighted triclocarban and triclosan as ECs requiring further investigation. A sensitivity analysis revealed that soil sorption coefficient and soil organic carbon were the most important parameters that affected model variance (correlation coefficient –0.89 and –0.30, respectively), highlighting the significance of contaminant and soil properties in influencing risk assessments. This model can help to prioritize emerging contaminants of concern requiring vigilance in environmental compartments.     

Distribution,Levels, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Singed Cattle Hide

Human beings are exposed to polycyclic aromatic hydrocarbons (PAHs) from various occupational, environmental, and dietary sources. The study was carried out in the Cape Coast Metropolis of Ghana to assess the levels of PAHs in treated and untreated cattle hide and the associated health risks thereof. Treated cattle hide (wele) is one of the most well-patronized meat products in Ghana. A total of 90, treated (n = 36), untreated (n = 36), and control (n = 18) cattle hide samples were treated and analyzed using a gas chromatography flame ionization detection (GC/FID) technique. The total PAH concentration in the treated cattle hide ranged from 5.9 μg/kg naphthalene to 719.9 μg/kg benzo[b]fluoranthene. The total PAHs in untreated hide ranged from 57.6 μg/kg naphthalene to 19840.9 μg/kg benzo[b]fluoranthene. The amount of PAHs in the control hide, however, ranged from non-detectable for many of the PAHs to 0.5 μg/kg for fluorene. The carcinogenic risk value associated with the consumption of treated hide in children ranged between 1.0 × 10^?3 and 9.4 × 10^?3 whereas that of adults ranged between 1.9 × 10^?4 and 2.1 × 10^?5. This implies that the continuous consumption of heavily burnt cattle hide may not exempt the consumers from all the possible health cases associated with PAHs.     

Environmental and Human Health Risk Assessment of Benzo(a)pyrene Levels in Agricultural Soils from the National Capital Region,Delhi, India

ABSTRACT

Exposure to benzo(a)pyrene (B(a)P) for health risk was studied in soils from the Delhi region, India. The mean and median concentrations of benzo(a)pyrene were 0.031 and 0.029 (±0.002) mg/kg, respectively. The lifetime average daily dose (LADD) for adults and children was 1.7 × 10^?8 mg kg^?1 d^?1 and 7.5 × 10^?8 mg kg^?1 d^?1, respectively, with incremental life time cancer risk (ILCR) of 1.2 × 10^?7 and 5.5 × 10^?7, respectively. The Index of Additive Cancer Risk (IACR) was 0.084. Our screening-level risk assessment shows that the observed ILCR and IACR values are much lower than the guideline values of 10^?6 ? 10^?4 (ILCR) and <1 (IACR), respectively, and therefore the measured B(a)P levels in soil may not portend environmental and human health risks.     

Human health risk from exposure to metals through fish and shellfish ingestion in Saudi Arabia

Abstract

In this study, human exposure and risks of metals through fish ingestion were predicted. Concentrations of 10 metals (Cd, As, Cr, Cu, Hg, Mn, Ni, Pb, V, and Zn) in 17 commonly eaten fish species in Saudi Arabia were characterized. Using the fish ingestion patterns, chronic daily intakes of metals among the Saudi and expatriate populations were predicted to be in the ranges of 8.89?×?10^?06–1.08?×?10^?02 and 6.59?×?10^?06–7.97?×?10^?03?mg/kg/day, respectively. The average cancer risks from inorganic arsenic were 2.76?×?10^?05 and 2.09?×?10^?05 for Saudi and expatriate, and the ranges were 1.61?×?10^?09–1.58?×?10^?03 and 2.64?×?10^?09–1.27?×?10^?03, respectively. The predicted risks were much lower than the previously reported risks. There were 47.4% and 42.4% chances that cancer risks would be higher than 1.0?×?10^?05 (10 per million) among Saudi and expatriate, respectively. The average cumulative hazard index (HI) for Saudi and expatriate were 0.324 and 0.239 with the ranges of 0.0142–7.26 and 0.017–6.43, respectively. Approximately 3.06% and 1.56% cases among Saudi and expatriate had HI greater than unity, indicating possible health concern, respectively. Through comprehensive understanding of exposure and risks, strategies can be adopted to protect human health.     

Risk Assessment of Aflatoxin B1 from Food Consumption in the Korean General Population

Levels were evaluated of Aflatoxin B₁ (AFB1) exposure through the intake of AFB1-contaminated foods among Koreans. Average daily intake, excess cancer risk, and population risk of AFB1 from food intake were calculated from Koreans with age greater than 20 years. Average daily intake of AFB1 by food ingestion was 0.064 ～ 0.361 ng/kg bw/ day. Excess cancer risk of AFB1 in food with the surface antigen of the hepatitis B-virus negative (HBsAg^?) and positive (HBsAg⁺) population was 5.76 × 10^{? 7}～ 3.25 × 10^{? 6} and 1.47 × 10^{? 5}～ 8.31 × 10^{? 5}, respectively. Application of JECFA's two tentative maximum levels (MLs) (10 μ g/kg and 20 μ g/kg) resulted in the population risk of 0.0009 ～ 0.0075 and 0.0014 ～ 0.0079 cancers/year/100,000 people, respectively, indicating that lower ML does not give a significant reduction of the risk. However, because Korea has a high incidence of HBsAg⁺ individuals, adoption of lower ML may be a reasonable decision to protect a high risk group. This is the first report on the risk assessment of AFB1 in food among the Korean population. Our study will contribute to providing the solid basis of establishing the maximum levels of AFB1 exposure through food ingestion in Korea as well as other countries.     

Health Risk Assessment of Chemical Mixtures Exposure to Residents in the Lake Taihu Region,China

This study assessed the mixture health risk for the residents of China's Lake Taihu region posed by a Persistent Organic Pollutants (POPs) mixture of dichloro-diphenyl-trichloroethane (DDT) and hexachlorocyclohexane (HCH). Multiple-pathway exposure models were used for exposure assessment in order to estimate the DDT and HCH exposure dose. The DDT and HCH PBPK models were developed and used for consequence assessment in order to analyze the pollutant distribution and accumulation process in human tissues. The tissue dose hazard index (HI) was used to estimate the mixture health risk. The results showed that the total exposure doses for male residents and female residents were 4.01 × 10^{? 4}～ 7.67 × 10^{? 3} mg/kg/day and 3.73 × 10^{? 4}～ 6.75 × 10^{? 3} mg/kg/day for DDT, respectively, and 3.78 × 10^{? 4}～ 5.14 × 10^{? 3} mg/kg/day and 3.53 × 10^{? 4}～ 4.66 × 10^{? 3} mg/kg/day for HCH, respectively. The maximum tissue concentrations in fat for male and female residents reached 110.51 mg/l and 97.21 mg/l for DDT, respectively, and 189.66 mg/l and 171.72 mg/l for HCH, respectively. The tissue dose hazard indexes for male and female residents were 0.1472 ～ 2.4990 and 0.1377 ～ 2.2230, respectively, and the probabilities of the risk exceeding the acceptable risk (HI = 1) for male and female were 24.60% and 16.51%, respectively.     

Trihalomethanes in desalinated water: Human exposure and risk analysis

Desalinated seawater is used to satisfy domestic water demands in many countries. The treated freshwater is blended with desalinated water to increase the water supply. The desalinated and blended water contains disinfection byproducts (DBPs), some of which may induce cancer risk to human. In this study, concentrations of trihalomethanes (THMs) in desalinated and blended water in Saudi Arabia were investigated, and human exposure and risk were predicted. The intakes of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) were predicted to be 8.38 × 10^?5, 7.57 × 10^?5, 2.54 × 10^?5, and 4.32 × 10^?4 mg/kg-d, respectively. The overall cancer risk and hazard index were estimated to be 1.78 × 10^?5 (range: 7.40 × 10^?7–9.26 × 10^?5) and 3.49 × 10^?2 (range: 1.20 × 10^?3–2.34 × 10^?1), respectively. The probabilities of cancer risk exceeding the risk levels of 1 × 10^?6, 1 × 10^?5, and 5.0 × 10^?5 were 1.0, 0.775, and 0.012, respectively. The loss of disability adjusted life years (DALYs) was predicted to be 25.1 per year while the cancer risk represented 8.48 × 10^?7 DALY per person per year. The financial burden from such risk was estimated to be US$ 2.72 (range: US$ 2.52–2.91) million per year. The findings may assist in better understanding and reducing cancer risk from DBPs in desalinated and blended water.     

Peroxyoxalate chemiluminescent assay for oxidase activities based on detecting enzymatically formed hydrogen peroxide

A sensitive peroxyoxalate chemiluminescent (PO-CL) assay for activities of oxidases (uricase, choline oxidase, cholesterol oxidase and xanthine oxidase) which catalyse a formation of hydrogen peroxide was developed using 4,4′-oxalyl-bis[(trifluoromethylsulphonyl)imino]trimethylene-bis(4-methylmorpholinium)trifluoromethanesulphonate as a chemiluminogenic reagent and 2,4,6,8-tetramorpholinopyrimido[5,4-d]pyrimidine as a fluorophore. The standard curve for hydrogen peroxide was linear over the range 1 × 10^?7-1 × 10^?4 mol/L. Relative standard deviations for oxidase assays were 5.1–12.7% (n = 10). Detection limits were 1 × 10^?3 U/mL for uricase, 5 × 10^?4 U/mL for choline oxidase, 5 × 10^?3 U/mL for cholesterol oxidase and 5 × 10^?4 U/mL xanthine oxidase (sample to blank ratio, 3).     

A novel chemiluminescent method for determination of phloroglucinol

It was found that the inhibition and enhancement by phloroglucinol of the chemiluminescence from the luminol–K₃Fe(CN)₆ system were dependent on the pH of luminol solution and the concentration of phloroglucinol. In Na₂CO₃–NaHCO₃ buffer, phloroglucinol exhibited strong chemiluminescent enhancement at pH 9.4. On this basis, a flow injection method was developed for the determination of phloroglucinol. The method was simple, rapid, convenient and sensitive, with a detection limit of 2.0 × 10^?9 mol/L. It is effective for determining phloroglucinol in the range of 1.0 × 10^?5–5.0 × 10^?9 mol/L. The relative standard deviation is 1.3% within one day and 3.2% between days for the determination of 5.0 × 10^?7 mol/L phloroglucinol. The method has been successfully used to determine phloroglucinol in environmental water, with satisfactory results. Copyright © 2003 John Wiley & Sons, Ltd.     

Dark respiration of the stipe of Ecklonia cava (Laminariales, Phaeophyta) in relation to temperature

Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) with a stipe length of 22–102 cm were collected at 6–9 m depth in Nabeta Bay, Shimoda, central Japan by scuba diving in February (winter) and in August (summer) 1998. Dark respiration of the intact stipe of E. cava was measured at various water temperatures ranging from 15 to 27.5°C in winter and 15–30°C in summer in a closed system by using a dissolved oxygen meter. The stipe respiration was compared on whole stipe, length, surface area, volume, wet weight and dry weight bases. On each basis, the stipe respiration always increased with a rise in water temperature within the temperature range investigated. The stipes showed similar respiration rates on each basis of length, surface area, volume, wet weight and dry weight at each temperature, irrespective of the stipe length. The mean respiration rates in winter (at 15–27.5°C) were: length, 16.7–32.5 μL O₂ cm^?1 h^?1; surface area, 3.2–6.2 μL O₂ cm^?2 h^?1; volume, 7.6–15.0 μL O₂ cm^?3 h^?1; wet weight, 6.2–12.2 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 43.8–88.0 μL O₂ g (dry weight)^?1 h^?1. Those for summer (at 15–30°C) were: length, 17.1–32.0 μL O₂ cm^?1 h^?1; surface area, 3.6–6.8 μL O₂ cm^?2 h^?1; volume, 9.7–18.7 μL O₂ cm^?3 h^?1; wet weight, 7.6–14.6 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 49.4–95.8 μL O₂ g (dry weight)^?1 h^?1. This is the first report of the intact stipe respiration of E. cava at various temperatures.     

Probabilistic Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Produced Water

The produced water extracted during oil and gas production includes formation water, injected water, small volumes of condensed water, and any chemical added during the oil/water separation process. Produced water contains both organic and inorganic constituents, and several studies have been conducted in the past to assess their risk. The toxicity and persistence of polycyclic aromatic hydrocarbons (PAHs) in produced water is of particular environmental concern, but there are very few studies on human health risk assessment from PAHs of produced water. This article summarizes the results of a conservative human health risk assessment approach for PAHs in produced water discharges to the marine environment. Due to the absence of available toxicity data for PAHs, the cancer slope factors were determined by using the relative potency factors (RPF) and Toxicity Equivalency Factors (TEF). Using the concentration distribution factors, the maximum cancer risks to humans were predicted in the range of 4.07 × 10^?7 to 2.95 × 10^?6. The 95th-percentile values show that the risks are well within the acceptable limits.     

DDT and HCH (Organochlorine Pesticides) in Residential Soils and Health Assessment for Human Populations in Korba,India

Dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (HCH), and their isomers’ levels in residential soils were determined for the assessment of health risk in Korba, India. Observed concentrations of total HCH and total DDT in soils were more or less comparable with other parts of India and the world. ΣHCH and ΣDDT concentrations ranged between 0.9–20 μg kg^?1 and 2–315 μg kg^?1, respectively, which were lower than recommended soil quality guidelines indicating low ecotoxicological risk. Carcinogenic and non-carcinogenic impacts of HCH and DDT on human populations through soil ingestion were evaluated and presented. The incremental lifetime cancer risk (ILCR) for adults and children ranged between 7.8 × 10^?10–1.6 × 10^?7 and 4.1 × 10^?9–8.2 × 10^?7, respectively. Non-cancer health hazard quotient (HQ) ranged between 5.9 × 10^?7–1.8 × 10^?3 and 3.1 × 10^?6–9.4 × 10^?3, respectively, for adults and children. The estimated ILCR and HQ were within the safe acceptable limits of 10^?6–10^?4 and ≤1.0, respectively, indicating low risk to human populations from exposure to organochlorine pesticides (HCH and DDT) in the study area.     

Comparative effects of adenine analogs upon metabolic cooperation between Chinese hamster cells with different levels of adenine phosphoribosyltransferase activity

Colony formation by variant Chinese hamster cells highly resistant to adenine analogs and deficient in adenine phosphoribosyltransferase (APRT) activity was measured after co-cultivation with APRT⁺, CHO-K1 cells in medium containing one of three different adenine analogs. Depending upon the density of APRT⁺ cells and the specific adenine analog, large differences in the recovery of APRT^? colonies were observed. The particular adenine analog and APRT⁺ cell density were more significant factors in the recovery of APRT^? colonies than the concentration of the analog or the level of APRT activity. The number of wild-type cells (CHO-K1) required to inhibit formation of APRT^? colonies by 50% (mean lethal density; MLD₅₀) with 65 μg/ml 8-aza-adenine (AzA) as the selective drug was 8.0 × 10⁵ cells/100 mm dish (1.5 × 10⁴/cm²). With 100 μg/ml 2,6-diaminopurine (DAP) the MLD₅₀ for CHO-K1 was 4.0 × 10⁵ cells/100 mm dish (7.3 × 10³/cm²). The MLD₅₀ for CHO-K1 when the DAP concentration was decreased to 50 μg/ml was only slightly higher, 5 × 10⁵ cells/100 mm dish (9.1 × 10³/cm²). The most toxic effect was observed with 2-fluoroadenine (FA). The MLD₅₀ for CHO-K1 in 2 μg/ml FA was 4.5 × 10⁴ cells/100 mm dish (8.2 × 10²/cm²), a cell density which permits minimal direct contact between APRT⁺ and APRT^? cells. The toxic effects of FA on individually resistant, APRT^? cells were found to be mediated by metabolites released into the medium by dying APRT⁺ cells. This metabolite toxicity to APRT^? cells was also demonstrated in mixtures with cells having only 8% of wild-type APRT activity. The MLD₅₀ for these APRT⁺ (8%) cells in 2 μg/ml FA was 7.5 × 10⁴ cells/100 dish (1.4 × 10³/cm²), a small difference from the MLD₅₀ for cells with wild-type levels of APRT activity. The differences in the recovery of APRT^? colonies from mixtures with APRT⁺ cells in these three adenine analogs are critical to the design of procedures for the selection of APRT^? cells from populations of APRT⁺ cells and emphasize the importance of establishing the parameters of metabolic cooperation, not only in terms of cell density but also with regard to the particular selective agent, in any experiment designed to determine precise mutation rates or to test putative mutagens upon mammalian cells in culture.     

Distribution Characteristics and Risk Assessments of PAHs in Fish from Lake Taihu,China

The concentrations of PAHs in four species of fish (Common carp, Crucian carp, Bighead carp, and Topmouth culter) from Lake Taihu were tested, and the human health risks of PAHs by fish consumption were evaluated. Results showed that concentrations of PAHs in fish from Lake Taihu were 52.5–247.6 ng/g wet weight (ww), and the BaP equivalent concentrations of total PAHs (B[a]P_eq) were 0.2–0.6 ng/g ww, which were less than the screening value of 2.6 ng/g wet for human consumption. The concentration sequences of PAHs in fish from Lake Taihu from high to low were Bighead carp > Crucian carp > Common carp > Topmouth culter. The human health risk level of PAHs by fish consumption was 5.8 ± 2.5 × 10^?6, which was less than the maximum acceptable risk level of 1 × 10^?5 for human health set by the U.S. Environmental Protection Agency. The tissue residue guideline (TRG) of PAHs for protecting aquatic wildlife was 1.3 mg/kg diet ww, which was higher than the concentrations of PAHs in fish from Lake Taihu. The results indicated that fish consumption from Lake Taihu would not cause health risk or harmful effects on wildlife that consume aquatic biota.     

Estimation of Excess Cancer Risk on Time-Weighted Lifetime Average Daily Intake of PAHs from Food Ingestion

The purposes of this study were to quantify the time-weighted, lifetime average, daily intake (LADI) of polycyclic aromatic hydrocarbons (PAHs) through food ingestion and to estimate the excess cancer risk based on lifetime dietary PAH intake. Twenty-seven different food commodities were selected from the 2001 Korean National Health and Nutrition survey based on their frequent consumption and high PAH level. The foods were analyzed for the profile of 14 PAH congeners using high performance liquid chromatography (HPLC) and fluorescence detector. Considering the toxic equivalent (TEQ) level converted with the toxic equivalent factors (TEFs), the highest total TEQ level of PAHs in foods was detected from roasted laver at 1.2 ug TEQ/kg. For the PAH exposure assessment according to ingested foods, the average body weight was separated according to the following age groups, 1–6, 7–19, 20–64 and over 64 years, and the daily food ingestion rates from the National Health and Nutrition survey were used. The estimated Lifetime Average Daily Intake (LADI) of PAHs was 3.22 × 10^–3 ug/kg/day for carcinogenic effects and was higher in the younger age groups under 20 years old than in the older groups. The dietary excess cancer risk estimated using the cancer potency of benzo(a)pyrene (7.3(mg/kg/day)^?1) was 2.3 × 10^?5, which is equivalent to a probability of tumor eruption in the upper gastrointestinal tract of two per hundred thousand persons.     

Hydrochemical,bacteriological assessment,and classification of groundwater quality in Thulamela Municipality,South Africa: potential health risk

Abstract

Potential effects of anthropogenic activities on different boreholes around Thulamela Municipality, South Africa, were evaluated by quantifying the bacteria indicators and physicochemical parameters during summer, autumn, and winter. The purpose was to determine whether the borehole water in this region is safe for domestic use across the seasons. The concentrations of physicochemical (Temperature, pH, electrical conductivity (EC), turbidity, and nitrate) and bacteriological (both Escherichia coli and Enterococcus faecalis) contaminants in the borehole water samples were determined using standard microbiology methods. The mean concentration of NO₃ for most of the boreholes failed to comply with the recommended guidelines throughout the season. High microbial load of E. coli (2.0?×?10¹ – 4.6?×?10³ CFU/100?ml) and E. faecalis (2.0?×?10° – 6.0?×?10² CFU/100?ml) was recorded in the wet season than in the dry season (0.0 – 7.0?×?10² and 0.0 – 1.0?×?10¹ CFU/100?ml, respectively). Sanitary inspection and water source classification showed that most boreholes are prone to chemical contaminants during summer and autumn due to rainfall and this correlates with the measured microbial contamination. The result is significantly important because water from these boreholes is used for domestic purposes without treatment and could pose major public health risks to the consumers.     

Distribution,sources, and health risk assessment of polycyclic aromatic hydrocarbons in dust from urban environment in the Niger Delta,Nigeria

The concentrations of the 16 U.S. Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) were measured in urban street dust with a view to understanding the potential risk to urban residents exposed to street dust, sources, and distribution of the PAHs. Gas chromatography–mass spectrometry was used to measure the concentrations of the PAHs after ultra-sonication with hexane/dichloromethane and clean up. The total concentrations of the ?16 PAHs in the urban street dust from Warri and its environs ranged from 165.1 to 1012 µg kg^?1. The isomeric ratios and the PCA indicated that combustion of petroleum and biomass are the major sources of PAHs in Warri and its environs. The total BaP carcinogenic and mutagenic potency concentrations (?BaP_TEQ and ?BaP_MEQ) were in the range of 0.03 to 219 µg kg^?1 and 0.52 to 182 µg kg^?1, respectively. The incremental life cancer risk from exposure of the residents of Warri and its environs ranged from 4.07 × 10^?7 to 3.11 × 10^?3 and 2.13 × 10^?7 to 1.49 × 10^?3 for the children and adults, respectively, which were higher than the baseline value of acceptable risk of 10^?6 (i.e., one case per million people).     

Heterologous expression,purification, and biochemical characterization of a greenbug (Schizaphis graminum) acetylcholinesterase encoded by a paralogous gene (ace‐1)

Acetylcholinesterase is a critical enzyme in the regulation of cholinergic neurotransmission in insects. To produce Schizaphis graminum acetylcholinesterase‐1 for structure–function analysis, we constructed a recombinant baculovirus to infect Sf9 cells, which secreted the soluble protein at a final concentration of 4.0 mg/L. The purified enzyme had an apparent M_r of 70 and 130 kDa in the reducing and nonreducing SDS‐polyacrylamide gels, respectively, indicating that it formed a dimer via an intermolecular disulfide bond. The fresh enzyme had a specific activity of 245 U/mg, which stabilized at a lower level (115 U/mg) in storage. The Michaelis constant and maximum velocity were 88.3 ± 9.6 μM and 133.2 ± 1.6 U/mg for acetylthiocholine iodide, 113.9 ± 12.5 μM and 106.4 ± 3.0 U/mg for acetyl(β‐methyl)thiocholine iodide, 68.9 ± 7.8 μM and 76.7 ± 1.0 U/mg for propionylthiocholine iodide, and 201.1 ± 21.0 μM and 4.4 ± 0.1 U/mg for S‐butyrylthiocholine iodide, respectively. The IC₅₀ values (5 min, room temperature) of ethopropazine, BW284C51, carbaryl, eserine, malaoxon, and paraoxon were 102, 1.66, 0.94, 0.20, 0.061, 0.016 μM, respectively. The bimolecular reaction constants (k_i) were (6.50 ± 0.40) × 10⁴ for carbaryl, (1.00 ± 0.16) × 10⁵ for eserine, (4.70 ± 0.13) × 10⁵ for malaoxon, and (9.06 ± 0.23) × 10⁵ M^?1 min^?1 for paraoxon. The enzyme was also inhibited by one of its products, choline, at concentrations higher than 20 mM, suggesting that choline bound to an anionic site and regulated the enzymatic activity. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:51–59, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20311