Cancer and Non-Cancer Risk Assessment from Exposure to Arsenic,Copper, and Cadmium in Borehole,Tap, and Surface Water in the Obuasi Municipality,Ghana

Cancer and non-cancer risk assessment from exposure to As, Cd, and Cu by resident adults and children from different water sources in Obuasi Municipality, Ghana, were measured in this study in accordance with the U.S. Environmental Protection Agency's (USEPA's) Human Health Risk Assessment guidelines. The results of cancer health risk for resident adults in Obuasi exposed to As in their tap water for both Central Tendency Exposure (CTE) and Reasonable Maximum Exposure (RME) parameters, respectively, are 6.6 × 10^?4 and 5.5 × 10^?6. For resident children in Odumasi, we obtained 4.7 × 10^?1 (CTE) and 6.7 × 10^?1 (RME). The results of the study obtained in most cases were found to exceed the USEPA's acceptable cancer risk range of 1 × 10^?6 to 1 × 10^?4 (i.e., 1 case of cancer out of 1,000,000 people to 1 case of cancer out of 10,000 people). Similarly, the results of the non-cancer human health risk for both resident adults and children were also found in most cases to be greater than the USEPA's acceptable non-cancer human health hazard index of 1.     

Probabilistic risk assessment of inhalation of nickel-rich soil particulates on Jeju Island,Korea

The soils of Jeju Island contain naturally abundant nickel originating from prehistoric volcanic activity. Nickel is a known human carcinogen via inhalation exposure. A risk assessment of soil particle inhalation was conducted for the first time in Korea through the analysis of soil and air data obtained from agricultural sites. Sixteen sites in Jeju were selected—13 farms, 2 citrus orchards, and 1 ranch. Forty-four soil samples were taken from these sites and analyzed for nickel content. Total suspended solids (TSP) and particulate matter up to 10 µm in size (PM10) were measured directly from the agricultural sites, and nickel concentrations in TSP and PM10 were quantified for use in the inhalation risk assessment. We conducted a probabilistic inhalation risk analysis using monitoring data obtained from the 16 sites on Jeju Island. Risk assessment procedures followed both the Korean Ministry of Environment and the U.S. Environmental Protection Agency (USEPA) risk assessment methodologies. The cancer risk associated with inhalation followed by application of the Korean risk assessment approach ranged from 4.98 × 10^?9 to 3.43 × 10^?7, whereas the cancer risk associated with inhalation followed by application of the USEPA risk assessment approach ranged from 3.40 × 10^?9 to 3.74 × 10^?7. This study demonstrates that no carcinogenic risk is associated with inhalation in Jeju, based on a lower cancer risk limit of 10^?6.     

Health Risk Assessment of Petrol Station Workers in the Inner City of Bangkok,Thailand, to the Exposure to BTEX and Carbonyl Compounds by Inhalation

The occupational health risk of petrol station workers from exposure to BTEX and carbonyl compounds via inhalation was estimated in the inner city of Bangkok. Personal sampling was performed within the workers’ breathing zone using 2,4 dinitrophenylhydrazine cartridges and charcoal glass tubes connected to a personal air pump during eight working hours at six petrol stations. BTEX and carbonyl compounds were quantitatively analyzed by GC/FID and HPLC/UV, respectively. Of all detectable BTEX and carbonyl compounds, the levels of the four most prevalent compounds (benzene, ethylbenzene, formaldehyde, and acetaldehyde) were used to assess the lifetime cancer risk and 95% confidence interval of the risk levels were found to be totally higher than acceptable criteria for benzene (1.82 × 10^–4–2.50 × 10^–4), formaldehyde (7.81 × 10^–6–1.04 × 10^–5), ethylbenzene (4.11 × 10^–6–5.52 × 10^–6), and acetaldehyde (1.39 × 10^–6–2.45 × 10^–6). Thus, petrol station workers in the inner city of Bangkok have a potentially high cancer risk through inhalation exposure. With respect to the noncarcinogenic agents, toluene, m,p-xylene, o-xylene, and propionaldehyde, all non-cancer health risk were within hazard quotients of 1 and of acceptable risk.     

Evaluation of PAHs concentration and cancer risk assessment on human health in a roadside soil: A case study

Abstract

An explanatory study was carried out to divulge the sources, contamination level of different classes of Polycyclic Aromatic Hydrocarbons (PAHs) distribution and the impact of vehicular traffic on the roadside soil by assessing incremental lifetime cancer risk at each site to understand the potential health risk of nearby residents along the National Highway-2 Delhi–Kolkata India. Comparison of the cancer risk assessment was performed using Monte Carlo simulation for the entire study area. The results revealed 90% cancer risk value of 6.40?×?10^?5 and 6.5?×?10^?5 for children and adults, respectively, whereas, without simulation the Total Cancer Risk (TCR) for adults was 6.925?×?10^?5 and 6.220?×?10^?5 for children, observed maximum at the location (S5). The dilemma of risk assessment indicating profoundly contaminated soil. Comparison of PAHs concentration with the background values of PAHs ranged from 1.478 to 27.493?mg kg^?1. The (IP/BgP) ratio specified that the PAHs content of the highway roadside sample is preponderate by diesel vehicle emission, biomass combustion and coal combustion. The study clearly revealed and advocated the influence of organic and inorganic pollution, which aggravates and causes health issues to the nearby inhabitants. This study could also be advantageous to similar consequences seen elsewhere in the world.     

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.     

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.     

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.     

Bioaccessibility-Based Risk Assessment of PAHs in Soils from Sites of Different Anthropogenic Activities in Lagos,Nigeria Using the Fed Organic Estimation Human Simulation Test Method

The aim of this study was to carry out a bioaccessibility-based risk assessment of polycyclic aromatic hydrocarbons (PAHs) in soils from sites of different anthropogenic activities in Lagos, Nigeria. Using an in vitro gastrointestinal model—Fed Organic Estimation Human Simulation Test method (FOREShT), the concentration of bioaccessible 16 priority US Environmental Protection Agency (USEPA) PAHs in soils were determined. Total concentration of 16 priority USEPA PAHs was also determined. The concentration range was 702–253,922 ng g^?1 and 92–760 ng g^?1 for total and bioaccessible PAHs, respectively. For persons involved with activities at these sites no health risks were observed, based on bioaccessibility values of PAHs. Mean daily intake of PAHs from these soils were below the oral mean daily intake threshold for PAHs in food. Also, overall estimated theoretical cancer risk (2.5 × 10^?09, 6.5 × 10^?07, 5.5 × 10^?10, 2.7 × 10^?09, 6.5 × 10^?10, 9.5 × 10^?10, 2.0 × 10^?09, and 4.1 × 10^?07 for the eight sites based on their bioaccessible concentration) for exposure to PAHs in surface soils were below the health guidelines for extreme (1 × 10^?04) and normal (1 × 10^?06) exposures.     

An Assessment of Risk from Particulate Released from Outdoor Wood Boilers

Use of outdoor wood boilers (OWB) has increased due to cost of fossil fuels. OWB short stacks release particles close to the breathing level, producing high levels of particulate matter ≤2.5 μm in diameter (PM_2.5). This assessment determines OWB contribution to local cancer risk and estimates thresholds for acute non-cancer risks. Carcinogenic PAHs in wood smoke (PM_2.5) cancer risks range from 2.7 × 10^–3 for the upper bound scenario (95% UCL value of PM_2.5 (665 μg/m³)) to 7.6 × 10^–5 for the lower bound (mean (186 μg/m³)). These risks represent a 7-fold increase of acceptable cancer risk for the lower bound value and 2 orders of magnitude above acceptable levels for the upper bound values. Non-cancer effects such as asthma and cardiopathies include respiratory attacks, hospital emergency room visits, and hospitalizations. Inhaled dose acute risk thresholds of 96, 120, and 250 μg PM 2.5/6 hours are proposed. Operation of an OWB that emits 100 grams PM_2.5/h was modeled and found to increase the exposures that exceed the 120-μg-risk level at and in residences within 500 to 1000 feet. The increases are projected to occur during periods of poor air mixing due to decreased wind speeds or inversions. Our analysis proposes a 6-h PM_2.5 inhaled dose threshold to predict peak periods of unhealthy air quality instead of 24-h and annual averages standards, which mask peak emissions.     

Effect of soil matric potential on leaf water potential,diffusive resistance,growth and development ofGmelina arborea L. seedlings

Gmelina arborea L. seedling growth and diurnal stomatal opening (as measured by stomatal resistance) were studied at soil matric potential 0, -0.1 and -0.72 × 10^?5 Pa. Leaf area, leaf number, plant height and dry weights of the vegetative parts were significantly reduced as soil matric potential decreased from 0 to -0.72 × 10^?5 Pa. The growth responses followed the same trend as net assimilation rate and relative growth rate. The highest moisture stress induced leaf senescence and leaf fall. Leaf water potential decreased from - 2 × 10^?5 Pa to - 20 × 10^?5 Pa with increasing soil moisture stress. Results indicate that the diurnal stomatal opening is controlled by photon flux density when this species is grown at soil matrio potential 0 Pa. However, with decreasing soil matrio potential (- 0.10 and -0.72 × 10^?5 Pa) the internal plant water deficit appears to oontrol the stomatal opening.     

Exposure to Crystalline Silica Inhalation Among Construction Workers: A Probabilistic Risk Analysis

Crystalline silica and its presence in dust generated during various construction activities may pose a health hazard to construction workers. In this article, the occupational exposure to crystalline silica and the related long-term health (cancer and non-cancer) risks among construction workers from five different trades (activities) were evaluated using a probabilistic approach. The predicted 95th percentile of the excess lifetime cancer risk and hazard quotients for exposure to crystalline silica ranged from 4.5 × 10^?5 to 1.2 × 10^?4, and 15 to 37, respectively. The efficiency of the state-of-the-art technologies to reduce silica inhalation at construction sites are evaluated in the context of reduction in long-term health risks to the construction workers. The use of engineering controls and personal protective equipments to reduce the exposure to crystalline silica reduced the hazard quotient and excess lifetime cancer risk approximately by 65% and 78%, respectively. The sensitivity analyses showed that the exposure concentration of crystalline silica was the most significant parameter in both cancer and non-cancer risk estimates for the construction workers. The breathing rate, the exposure factor, and the daily shift hours also significantly contribute to the cancer and non-cancer risk estimates for the construction workers.     

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.     

Cancer and non-cancer health risk assessment associated with exposure to non-methane hydrocarbons among roadside vendors in Delhi,India

Abstract

This study estimates the cancer and non-cancer health risk among the roadside vendors in Delhi, the capital city of India. Air samples of selected NMHCs and their derivatives were collected from four different sites (one traffic intersection, one industrial, and two residential) in Delhi and were analyzed on Gas Chromatograph (GC) to obtain their atmospheric concentrations. At each site, a survey among the roadside vendors was also conducted to obtain information about their bodyweight and exposure to outdoor ambient air. The study reveals that hazard quotient of 1,3-butadiene is greater than one at all the sites, with its maximum value occurring at the industrial site. The major contributors to the workplace cancer risk (WCR) are found to be 1,3-butadiene and chloroform. The overall WCR is observed to be the highest (9.4?×?10^?4) at the traffic intersection site, followed by the industrial site (7.0?×?10^?4). Cancer incidence data and the population data are also used to estimate the growth of cancer risk in Delhi from 2009 to 2016. Comparison of the WCR values of the four sites with the cancer risk estimated from the cancer incidence data shows that NMHCs and their derivatives are significant contributors to the overall cancer risk in Delhi. Our results suggest that NMHCs and their derivatives need to be given due consideration in the National Cancer Control Programme of India.     

Two-Dimensional Monte Carlo Simulation and Beyond: A Comparison of Several Probabilistic Risk Assessment Methods Applied to a Superfund Site

Four different probabilistic risk assessment methods were compared using the data from the Sangamo Weston/Lake Hartwell Superfund site. These were one-dimensional Monte Carlo, two-dimensional Monte Carlo considering uncertainty in the concentration term, two-dimensional Monte Carlo considering uncertainty in ingestion rate, and microexposure event analysis. Estimated high-end risks ranged from 2.0×10^?4 to 3.3×10^?3. Microexposure event analysis produced a lower risk estimate than any of the other methods due to incorporation of time-dependent changes in the concentration term.     

Potential Health Risk of Reused Creosote-Treated Old Railway Ties at Recreational Sites in Korea

Old creosote-treated railway ties reused at recreational sites in Korea are potential hazards, due to the presence of harmful substances in creosote, such as polycyclic aromatic hydrocarbons (PAHs). In such sites, PAHs in ties can be leached or emitted, and human exposure might then occur. In this study, the concentrations of 16 PAHs in soil, air, and tie surfaces in old creosote-treated railway ties reused in recreational sites were investigated, and the potential health risk of the ties was evaluated through two exposure scenarios: a recreational scenario (ingestion of and dermal contact with soil and inhalation of soil particles) and a playground scenario (ingestion after contact and dermal contact with ties). For the recreational scenario, the health risks of PAHs were safe; however, for the playground scenario, the carcinogenic risk of ingestion after contact, and dermal contact with benz(a)anthracene and benzo(a)pyrene on the tie surfaces, exceeded the acceptable risk level (10^–6). For the carcinogenic risks of ingestion after contact with ties, the probabilities of cancer development were 8 and 5 in one million people for benz(a)anthracene and benzo(a)pyrene, respectively. The carcinogenic risks for dermal contact with ties were 2.4 × 10^–6 and 1.4 × 10^–6 for benz(a)anthracene and benzo(a)pyrene, respectively.     

Ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the water from a large Chinese lake based on multiple indicators

In the surface water of Lake Chaohu, China, the concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were measured by gas chromatograph–mass spectrometer (GC–MS). Based on the species sensitivity distribution (SSD) model and the probabilistic risk assessment (PRA) model, the indicators were calculated to assess the potential ecological risk of the individual and of multiple congeners of PAHs and their probabilities. The results revealed that the average residual level of the total PAHs (PAH₁₆) in the water ranged from 95.2 to 370.1 ng/L, with a mean value 181.5 ± 70.8 ng/L. The PAH content in the water was dominated by the low-molecular-weight congeners. The multi-substance potentially affected fractions (msPAFs) of the studied PAHs obtained by the SSD model varied from 0.29% (site B3) to 1.58% (site B6), with an average of 0.51 ± 0.34%. The average of the msPAFs (0.93%) for the inflow rivers was greater than that for the western (0.42%) and eastern (0.34%) parts of the lake. The greatest ecological risk probability calculated by the PRA model was found for Pyr (1.55%), followed by Ant (7.07 × 10⁻²%), Fla (2.21 × 10⁻²%), Phe (9.25 × 10⁻⁶%), Nap (1.01 × 10⁻⁵%), Flo (1.16 × 10⁻¹⁴%) and Ace (2.86 × 10⁻¹⁶%). The same order of ecological risks calculated by the two models was found for the studied PAH compounds. The toxicity data might be the primary source of the ecological risk uncertainties, as indicated by the greater values of coefficients of variation (CV) for the toxicity. This study concluded that the combinations of multiple indicators based on the SSD and PRA models for the ecological risk assessment are necessary to provide more general information on the spatial variations and the probabilities of potential ecological risks of the individual and multiple congeners of PAHs.     

Study of the Enantioselective Interaction of Diclofop and Human Serum Albumin by Spectroscopic and Molecular Modeling Approaches In Vitro

In this contribution, the enantioselective interactions between diclofop (DC) and human serum albumin (HSA) were explored by steady‐state and 3D fluorescence, ultraviolet‐visible spectroscopy (UV‐vis), and molecular modeling. The binding constants between R‐DC and HSA were 0.9213 × 10⁵, 0.9118 × 10⁵, and 0.9009 × 10⁵ L · mol^‐1 at 293, 303, 313 K, respectively. Moreover, the binding constants of S‐DC for HSA were 1.4766 × 10⁵, 1.2899 × 10⁵, and 1.0882 × 10⁵ L · mol^‐1 at 293, 303, and 313 K individually. Such consequences markedly implied the binding between DC enantiomers and HSA were enantioselective with higher affinity for S‐DC. Steady‐state fluorescence study evidenced the formation of DC‐HSA complex and there was a single class of binding site on HSA. The thermodynamic parameters (ΔH, ΔS, ΔG) of the reaction clearly indicated that hydrophobic effects and H‐bonds contribute to the formation of DC‐HSA complex, which was in excellent agreement with molecular simulations. In addition, both site‐competitive replacement and molecular modeling suggested that DC enantiomers were located within the binding pocket of Sudlow's site II. Furthermore, the alterations of HSA secondary structure in the presence of DC enantiomers were verified by UV‐vis absorption and 3D fluorescence spectroscopy. This study can provide important insight into the enantioselective interaction of physiological protein HSA with chiral aryloxyphenoxy propionate herbicides and gives support to the use of HSA for chiral pesticides ecotoxicology and environmental risk assessment. Chirality 25:719–725, 2013. © 2013 Wiley Periodicals, Inc.     

Health Risks of Heavy Metals through Consumption of Greenhouse Vegetables Grown in Central Iran

Elevated heavy metal (HM) concentrations in vegetables may pose serious health risks to humans. There is limited information on health risks associated with HM contaminants in greenhouse vegetables. The objective of this study was to estimate the health risks of Pb, Cd, Ni, and Cr via consumption of greenhouse cucumbers and bell peppers produced in Iran using the total non-cancer hazard quotient (THQ) and cancer risk assessment estimates. Cadmium, Pb, Ni, and Cr concentrations in the vegetables varied from < 0.02 to 0.05, 0.19 to 0.64, 0.16 to 0.20 and 0.07 to 0.13 μg g^?1, respectively. Individual metal THQ values indicate the relative absence of non-cancer health effects associated with intake of a single metal through consumption of either cucumbers or bell peppers. The THQ for all population groups via consumption of greenhouse cucumbers and bell peppers was smaller than 1.0, which shows low possibility of any obvious risk. The result showed that Cd is the major risk contributor for the consumers. The cancer risk assessment for Pb for Qom adult populations groups via consumption of cucumbers and bell peppers was greater than 1 × 10^?6. High Pb and Cd concentration in the greenhouse vegetables is an important concern that has to be considered.     

Kinetics of phosphate uptake in excised maize root

The short term uptake of phosphate involving 10 min absorption followed by 5 min desorption, both at 30 °C, in the concentration range 1.0×10^?9 to 7.5×10^?2 M KH₂PO₄ by fresh and washed maize (Zea mays L. cv. Ganga Safed-2) roots can be described by a single isotherm having five phases (0 and I–IV) with regularly spaced kinetic constants. Almost identical kinetics were observed in both fresh and washed maize roots. The kinetics of phase 0 in the concentration range 1.0×10^?9–3.0×10^?5 M. was sigmoidal in fresh maize roots, however, in washed tissue exhibited 2 phases termed here as 0a and 0b. 0a covered the concentration range 1.0×10^?9–5.0×10^?6 M and 0b 6.0×10^?6–3.0×10^?5 M. In the concentration range 1.0×10^?4–7.5×10^?2 M four distinct phases, termed as I, II, III and IV were evident in both fresh and washed maize roots. Each phase obeyed Michaelis—Menten kinetics. The values of K_m and V_max have been estimated for each phase. The uptake isotherm was accompanied by discontinuous transitions.     

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).