Significant Exposure Pathway Research Articles

Assessment of arsenic species in human hair, toenail and urine and their association with water and staple food.

Arsenic intake from household drinking/cooking water and food may represent a significant exposure pathway to induce cancer and non-cancer health effects. This study is based on the human biomonitoring of 395 volunteers from 223 households with private water sources located in rural Punjab, Pakistan. This work has shown the relative contribution of water and staple food to arsenic intake and accumulation by multiple biological matrix measurements of inorganic and organic arsenic species, while accounting for potential confounders such as age, gender, occupation, and exposure duration of the study population. Multi-variable linear regression showed a strong significant relationship between total arsenic (tAs) intake from water and concentrations of tAs, inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) in urine and toenail samples. tAs intake from staple food (rice and wheat) also showed a strong significant relationship with hair tAs and iAs. The sole impact of staple food intake on biomarkers was assessed and a significant correlation was found with all of the urinary arsenic metabolites. Toenail was found to be the most valuable biomarker of past exposure to inorganic and organic arsenic species of dietary and metabolic origin.

The sources and chemical content of edible soil sticks sold in markets in Tanzania: a cross-sectional analytical study.

Geophagy, or eating soil, is common in various countries including Tanzania. Studies have reported on the levels of different chemicals in consumed soil, some of which can be harmful to the health of individuals practicing geophagy. Dried soil sticks for eating, referred to as pemba, are commercially available in many markets in sub-Saharan Africa, but few studies have established the sources of the soils. The purpose of the current study was to: (1) systematically document the sources of the soils used in pemba commonly sold in regional markets throughout Tanzania using a global positioning system (GPS) to establish the supply chain flow of pemba to markets, and (2) assess the chemical element content of the soil sources for both water-extractable chemical element (WEC) and total chemical element (TC) contents. Surveys were conducted at regional markets across mainland Tanzania to identify the sources of soils commonly used in commercially available soil sticks. Then, soil samples were collected from identified sources in 12 regions across Tanzania and analyzed for WEC and TC content using an inductively coupled plasma mass spectrometry laboratory technique. Mining of the pemba soil was localized in 12 regions. Analysis of the supply chain flow revealed a well-established distribution network that ensured transportation and marketing of the soil sticks to regions throughout the country. WEC and TC of essential and trace elements (Ca, Fe, K, Mg, Na, Mn, Co, Cr, V, Mo, Cu, and Zn) and toxic elements (Al, As, Ba, Cd, Ni, and Pb) were detected at varying concentrations. Most of the trace and toxic elements were above the normal range, based on the oral maximum tolerable limits designated by the World Health Organization and US Agency for Toxic Substance and Disease Registry. This is the first study in Tanzania to document and examine the source soil locations for commercially available soil sticks at the macroscale across the entire country. The findings suggest that geophagy could be a significant exposure pathway for toxic elements.

Comparative overview of primary sedimentation-based mechanical stage in some Romanian wastewater treatment systems

Nowadays, wastewater (WW) treatment facilities are considered significant exposure pathways for solid particles, and also significant concerns of any quality conscious manufacturer. Most solid particles have some forms of organic coating either used as active material or to suspend and/or stabilize different present solid materials, having increase in toxicity that must be reduced, or sometimes even totally eliminated, especially if effluent is either discharged directly to surface water, or distributed through industrial water supplies. Representatives providing innovative technologies, comprehensive supports and expertise in wastewater and sludge treatment field are known, each one using modern treatment technology and facilities. Mechanical treatment is indispensable in primary treatment steps of both municipal and industrial WW applications, its main goal being separation of floating, settling and suspended materials (especially into a primary sedimentation-based treatment step).The aim of this work is to present comparatively the performance in solids removal of conventional mechanical WW treatment stages, especially those based on primary sedimentation, or sedimentation-like operations applied for Romanian urban WW treatment plants (serving two towns with ca 18,000 inhabitants), industrial WW treatment plants (deserving industries of vegetal food processing and organic chemicals’ manufacturing) and additional information on valorisation of separated solid material and improvement possibilities.

Bioaccumulation and biomagnification of ultraviolet absorbents in marine wildlife of the Pearl River Estuarine, South China Sea

Bioaccumulation and trophic transfer in ecosystems is an important criterion for assessing environmental risks of contaminants. This study investigated bioaccumulation and biomagnification of 13 organic ultraviolet absorbents (UVAs) in marine wildlife organisms in the Pearl River Estuary, South China Sea. The UVAs could accumulate in the organisms with biota - sediment accumulation factors (BSAF) of 0.003–2.152. UV531 was the most abundant and showed the highest tendency to accumulate in the organisms with a median BSAF of 1.105. The UVAs demonstrated species - and compound-specific accumulation in the marine organism. Fishes showed significantly higher capability than the cephalopods and crustaceans in accumulation of the UVAs. Habitat did not demonstrate obvious impact on accumulation of the UVA. On the other hand, benzophenone-3, UV328, and UV234 showed significantly higher concentration in the detritus feeding fishes than carnivorous and planktivorous fishes, suggesting governing effect of dietary habits of the organisms on bioaccumulation of these UVAs. Direct uptake from growth media was a significant exposure pathway of the organisms to the UVAs. The estimated trophic magnification factors and biomagnification factors revealed that UV329, UV531, and octocrylene could potentially biomagnify in the marine food web.

Food consumption survey of Shanghai adults in 2012 and its associations with phthalate metabolites in urine

BackgroundDiet is considered to be a significant exposure pathway for phthalates. In this study, we assessed the associations between food consumption and urinary concentrations of phthalate metabolites among Shanghai adults. MethodsA cross-sectional study involving 2418 participants was conducted in the fall of 2012. Recent food consumption was assessed by a 24-h dietary recall survey, and a Food Frequency Questionnaire (FFQ) characterized long-term dietary patterns. Urinary metabolites of six phthalates were measured. ResultsBoth the 24-h recall survey and FFQ identified wheat, dairy, and fruits as being positively associated with the excretion of phthalate metabolites. The 24-h recall data also showed positive associations with processed meats and alcohol. We evaluated the impact of reported consumption of multiple food categories simultaneously (wheat, fruits, meats, etc.) on metabolite excretion and found that, as more food types were consumed, the number of metabolites excreted, as well as their concentrations, increased with high significance (p values<0.0001). We also evaluated the two survey instruments together. When both surveys reported consumption of fruits and dairy, the numbers of metabolites and their concentrations were significantly higher compared to when both surveys reported non-consumption, (p values<0.000001). Rice consumption was found to be negatively associated with phthalate excretion; frequent and high levels of rice consumption were found to be associated with lower excretion of metabolites. ConclusionFood consumption was associated with phthalate exposure in Shanghai adults. Both 24-h recall and FFQ identified significant associations between consumption of food types and phthalate exposure.

Hydrogeochemistry of arsenic pollution in watersheds influenced by gold mining activities in Paracatu (Minas Gerais State, Brazil)

The aim of this study is to evaluate total arsenic (As) concentrations in drinking water (main pathway of human exposure) and its hydrogeochemical controls in the "Morro do Ouro" gold mine region, which is the largest gold mine in Brazil, characterized by gold-arsenopyrite association. Arsenic concentration was generally below the detection limit (LOD < 0.5μgL(-1)). Thus, water ingestion may not be a significant exposure pathway to local population. Low groundwater As concentrations (<1μgL(-1)) are likely due to ore body structural setting, which plunges from 10° to >20°, being readily covered by thick phyllites that are poor in As some hundreds of meters away from the mine. Thirty-five percent of As levels in superficial waters (<0.5 to 40μgL(-1)) were >10μgL(-1), which is the maximum permissible value for human ingestion. The highest concentrations were found nearby mine facilities and old artisanal mining areas surrounding the mine, decreasing downstream. Undisturbed watersheds showed As concentrations close to LOD. Hydrogeochemical data stress the sorption (adsorption and co-precipitation) of As role, mainly by Fe oxyhydroxides, as a geochemical filter that retains As, attenuating its concentration in both superficial and groundwater. Such minerals are abundant in the region oxisols, sediments, and phyllites and may form stable mineral complexes with As under the pH (mostly neutral) and Eh (reduced environment) conditions found in the field. It has been demonstrated that As(III) (more toxic) and As(V) co-exist in the analyzed waters and that As(V) predominates in superficial water.

Direct contact between dust and HBCD-treated fabrics is an important pathway of source-to-dust transfer

Hexabromocyclododecanes (HBCDs) are a class of brominated flame retardant that have found extensive application in consumer products used widely in indoor environments. Although uncertainty remains about the human health impacts of HBCDs, ingestion of HBCD-contaminated indoor dust has been shown to be a particularly significant exposure pathway for young children. Despite this, understanding of the mechanisms via which HBCD transfer from products to indoor dust remains incomplete. In this study, an in-house test chamber was used to investigate transfer of HBCDs from a treated textile sample to indoor dust via direct textile:dust contact. Results were compared with previous data using the same test chamber to examine other pathways via which HBCDs transfer from products to dust, and highlighted HBCD transfer via direct source:dust contact as being particularly important. This novel finding was corroborated by complementary experiments that examined HBCD transfer via direct contact, from other treated textiles to three major components of indoor dust: artificial indoor dust, soil particles, and cotton linters.

Contamination assessment and potential human health risks of heavy metals in Klang urban soils: a preliminary study

Urban areas with rapid industrial development have major impacts on environmental soil quality. This study was carried out to determine contamination assessment of heavy metal concentration of urban soil from Klang district (Malaysia). Health risk assessment was used to determine potential health risks (carcinogenic and non-carcinogenic risks) in both adults and children. Moreover, this study was also used to identify the most significant contaminant and exposure pathway with regard to Klang urban soil. Mean bioavailability of heavy metal concentrations were found in the order of Fe (6.65 mg/kg) > Zn (5.61 mg/kg) > Cu (2.96 mg/kg) > Co (0.22 mg/kg) > Cd (0.14 mg/kg) > Pb (0.11 mg/kg) > Cr (0.10 mg/kg). Maximum values of Cd (0.64 mg/kg), Cu (52.14 mg/kg) and Pb (9.18 mg/kg) have exceeded some guidelines and standard values. Study findings showed that total carcinogenic risks values of Cd, Cr and Pb are more than incremental lifetime (1.0E-05). This indicates the likehood of having cancer threat for adults and children. While for total non-carcinogenic risk, none of the heavy metals (Co, Cr, Cu, Pb and Zn) showed Hazard Index values more than one indicating there is no any potential non-carcinogenic risks for adults and children in study area. From this study, Cd is the most significant contaminant as maximum concentration value has exceeded soil guidelines and potential to have carcinogenic risks to adults and children. Pathway order for both carcinogenic and non-carcinogenic risks is ingestion > dermal > inhalation where ingestion pathway contributed the most to potential health risks involving urban soil of Klang.

Phthalates and diet: a review of the food monitoring and epidemiology data.

Phthalates are associated with a variety of health outcomes, but sources that may be targeted for exposure reduction messaging remain elusive. Diet is considered a significant exposure pathway for these compounds. Therefore, we sought to identify primary foods associated with increased exposure through a review of the food monitoring survey and epidemiological data. A search in PubMed and Google Scholar for keywords "phthalates" and "diet" "food" "food stuffs" "dietary intake" "food intake" and "food concentration" resulted in 17 studies measuring phthalate concentrations in United States (US) and international foods, three epidemiological association studies, and three interventions. We report on food groups with high (≥300 μg/kg) and low (<50 μg/kg) concentrations and compare these to foods associated with phthalate body burden. Based on these data, we estimated daily intakes of di-2-ethylhexyl phthalate (DEHP) of US women of reproductive age, adolescents and infants for typical consumption patterns as well as healthy and poor diets. We consistently observed high DEHP concentrations in poultry, cooking oils and cream-based dairy products (≥300 μg/kg) across food monitoring studies. Diethyl phthalate (DEP) levels were found at low concentrations across all food groups. In line with these data, epidemiological studies showed positive associations between consumption of meats, discretionary fat and dairy products and DEHP. In contrast to food monitoring data, DEP was found to be associated with intake of vegetables in two studies. DEHP exposure estimates based on typical diets were 5.7, 8.1, and 42.1 μg/kg-day for women of reproductive age, adolescents and infants, respectively, with dairy as the largest contributor to exposure. Diets high in meat and dairy consumption resulted in two-fold increases in exposure. Estimates for infants based on a typical diet exceeded the Environmental Protection Agency’s reference dose of 20 μg/kg-day while diets high in dairy and meat consumed by adolescents also exceeded this threshold. The review of the literature demonstrated that DEHP in some meats, fats and dairy products is consistently found in high concentrations and can contribute to exposure. Guidance on future research in this area is provided that may help to identify methods to reduce dietary phthalate exposures.

Temporal trends of perfluoroalkane sulfonic acids and their sulfonamide-based precursors in herring from the Swedish west coast 1991–2011 including isomer-specific considerations

A method was developed for simultaneous analysis of perfluoroalkane sulfonic acids (PFSAs) and their sulfonamide-based precursors (perfluoroalkane sulfonamidoacetic acids (FASAAs), sulfonamides (FASAs), and sulfonamidoethanols (FASEs)) in fish muscle. Extraction was performed with acetonitrile followed by a clean-up and fractionation step and instrumental analysis by UPLC/MS/MS and GC/MS. Time trends of PFSAs and their precursors in herring muscle samples originating from the Kattegat at the west coast of Sweden were investigated covering the years 1991–2011. The following analytes were detected, all with decreasing or unchanged trends between 1991 and 2011: Perfluorobutane sulfonic acid (PFBS, below the method detection limit (<MDL)-10pg/g), perfluorohexane sulfonic acid (PFHxS, 9–38pg/g), perfluorooctane sulfonic acid (PFOS, 240–930pg/g), perfluorodecane sulfonic acid (PFDS, <MDL-4pg/g), N-methyl and N-ethyl perfluorooctane sulfonamidoacetic acid (MeFOSAA and EtFOSAA, 2–39 and 2–31pg/g, respectively) and perfluorooctane sulfonamide (FOSA, 78–920pg/g). The highest concentrations were found for PFOS and FOSA around the turn of the century. Shorter disappearance half-lives were observed for precursors compared to PFSAs. Assuming that these trend differences are representative for fish consumed by the general Swedish population, this observation suggests that the relative contribution of precursors to total human exposure to PFOS via fish intake has decreased in Sweden over the study period. PFOS precursors in fish may have constituted a significant indirect exposure pathway for PFOS in the 1990s. Isomer-specific analysis of PFOS and FOSA revealed <10% relative contributions of branched isomers to total PFOS and total FOSA. Furthermore, the percentage branched isomers decreased over time for both compounds. These findings are contrary to patterns and temporal trends of PFOS isomers commonly found in human serum. In combination with literature data on isomer patterns in other edible fish species and on isomer-specific human toxicokinetics, our results suggest that fish consumption alone cannot account for the PFOS isomer patterns and trends observed in humans.

Biomarkers of arsenic exposure and effects in a Canadian rural population exposed through groundwater consumption

Drinking water intake of arsenic (As) from private wells may represent a significant exposure pathway and induce oxidative DNA damage. We measured total As concentrations in hair and nails, and concentrations of the different species of As and its metabolites as well as 8-OHdG in urine of 110 non-smoking adults living in a rural region of the Province of Quebec, Canada. Significant differences in exposure biomarker levels were observed between individuals consuming drinking water with As levels of≤1.0,>1.0 -≤10 and>10 μg/l. Multivariate linear regression analysis also showed a significant relationship between estimated daily drinking water intakes of As and biomarker levels. Conversely, 8-OHdG levels were not significantly related to daily drinking water intakes of As or to hair, nail or urinary exposure biomarker levels, according to multivariate linear regression analysis. Even at the relatively low levels of As found in well water of our participants, water consumption significantly increases their body load of As, as confirmed by multiple matrix measurements, which reflected exposure over different time frames. However, this increased internal As dose was not associated with higher oxidative damage to DNA as reflected by urinary 8-OHdG levels.

Human health risk assessment of lead from mining activities at semi-arid locations in the context of total lead exposure

Lead from historical mining and mineral processing activities may pose potential human health risks if materials with high concentrations of bioavailable lead minerals are released to the environment. Since the Joint Expert Committee on Food Additives of Food and Agriculture Organization/World Health Organization withdrew the Provisional Tolerable Weekly Intake of lead in 2011, an alternative method was required for lead exposure assessment. This study evaluated the potential lead hazard to young children (0-7 years) from a historical mining location at a semi-arid area using the U.S. EPA Integrated Exposure Uptake Biokinetic (IEUBK) Model, with selected site-specific input data. This study assessed lead exposure via the inhalation pathway for children living in a location affected by lead mining activities and with specific reference to semi-arid conditions and made comparison with the ingestion pathway by using the physiologically based extraction test for gastro-intestinal simulation. Sensitivity analysis for major IEUBK input parameters was conducted. Three groups of input parameters were classified according to the results of predicted blood concentrations. The modelled lead absorption attributed to the inhalation route was lower than 2 % (mean ± SE, 0.9 % ± 0.1 %) of all lead intake routes and was demonstrated as a less significant exposure pathway to children's blood, compared with ingestion. Whilst dermal exposure was negligible, diet and ingestion of soil and dust were the dominant parameters in terms of children's blood lead prediction. The exposure assessment identified the changing role of dietary intake when house lead loadings varied. Recommendations were also made to conduct comprehensive site-specific human health risk assessment in future studies of lead exposure under a semi-arid climate.

A prospective case–control and molecular epidemiological study of human cases of Shiga toxin-producing Escherichia coli in New Zealand

BackgroundShiga toxin-producing Escherichia coli (STEC) O157:H7 and related non-O157 STEC strains are enteric pathogens of public health concern worldwide, causing life-threatening diseases. Cattle are considered the principal hosts and have been shown to be a source of infection for both foodborne and environmental outbreaks in humans. The aims of this study were to investigate risk factors associated with sporadic STEC infections in humans in New Zealand and to provide epidemiological information about the source and exposure pathways.MethodsDuring a national prospective case–control study from July 2011 to July 2012, any confirmed case of STEC infection notified to regional public health units, together with a random selection of controls intended to be representative of the national demography, were interviewed for risk factor evaluation. Isolates from each case were genotyped using pulsed-field gel electrophoresis (PFGE) and Shiga toxin-encoding bacteriophage insertion (SBI) typing.ResultsQuestionnaire data from 113 eligible cases and 506 controls were analysed using multivariate logistic regression. Statistically significant animal and environmental risk factors for human STEC infections were identified, notably 'Cattle livestock present in meshblock’ (the smallest geographical unit) (odds ratio 1.89, 95% CI 1.04–3.42), 'Contact with animal manure’ (OR 2.09, 95% CI 1.12–3.90), and 'Contact with recreational waters’ (OR 2.95, 95% CI 1.30–6.70). No food-associated risk factors were identified as sources of STEC infection. E. coli O157:H7 caused 100/113 (88.5%) of clinical STEC infections in this study, and 97/100 isolates were available for molecular analysis. PFGE profiles of isolates revealed three distinctive clusters of genotypes, and these were strongly correlated with SBI type. The variable 'Island of residence’ (North or South Island of New Zealand) was significantly associated with PFGE genotype (p = 0.012).ConclusionsOur findings implicate environmental and animal contact, but not food, as significant exposure pathways for sporadic STEC infections in humans in New Zealand. Risk factors associated with beef and dairy cattle suggest that ruminants are the most important sources of STEC infection. Notably, outbreaks of STEC infections are rare in New Zealand and this further suggests that food is not a significant exposure pathway.

Linking geological and health sciences to assess childhood lead poisoning from artisanal gold mining in Nigeria.

Background: In 2010, Médecins Sans Frontières discovered a lead poisoning outbreak linked to artisanal gold processing in northwestern Nigeria. The outbreak has killed approximately 400 young children and affected thousands more.Objectives: Our aim was to undertake an interdisciplinary geological- and health-science assessment to clarify lead sources and exposure pathways, identify additional toxicants of concern and populations at risk, and examine potential for similar lead poisoning globally.Methods: We applied diverse analytical methods to ore samples, soil and sweep samples from villages and family compounds, and plant foodstuff samples.Results: Natural weathering of lead-rich gold ores before mining formed abundant, highly gastric-bioaccessible lead carbonates. The same fingerprint of lead minerals found in all sample types confirms that ore processing caused extreme contamination, with up to 185,000 ppm lead in soils/sweep samples and up to 145 ppm lead in plant foodstuffs. Incidental ingestion of soils via hand-to-mouth transmission and of dusts cleared from the respiratory tract is the dominant exposure pathway. Consumption of water and foodstuffs contaminated by the processing is likely lesser, but these are still significant exposure pathways. Although young children suffered the most immediate and severe consequences, results indicate that older children, adult workers, pregnant women, and breastfed infants are also at risk for lead poisoning. Mercury, arsenic, manganese, antimony, and crystalline silica exposures pose additional health threats.Conclusions: Results inform ongoing efforts in Nigeria to assess lead contamination and poisoning, treat victims, mitigate exposures, and remediate contamination. Ore deposit geology, pre-mining weathering, and burgeoning artisanal mining may combine to cause similar lead poisoning disasters elsewhere globally.

The effect of misunderstanding the chemical properties of environmental contaminants on exposure beliefs: A case involving dioxins

Chemical properties of contaminants lead them to behave in particular ways in the environment and hence have specific pathways to human exposure. If residents of affected communities lack awareness of these properties, however, they could make incorrect assumptions about where and how exposure occurs. We conducted a mailed survey of 904 residents of Midland and Saginaw counties in Michigan, USA to assess to what degree residents of a community with known dioxin contamination appear to understand the hydrophobic nature of dioxins and the implications of that fact on different potential exposure pathways. Participants assessed whether various statements about dioxins were true, including multiple statements assessing beliefs about dioxins in different types of water. Participants also stated whether they believed different exposure pathways were currently significant sources of dioxin exposure in this community. A majority of residents believed that dioxins can be found in river water that has been filtered to completely remove all particulates, well water, and even city tap water, beliefs which are incongruous with the hydrophobic nature of dioxins. Mistrust of government and personal concern about dioxins predicted greater beliefs about dioxins in water. In turn, holding more beliefs about dioxins in water predicted beliefs that drinking and touching water are currently significant exposure pathways for dioxins. Ensuring that community residents' mental models accurately reflect the chemical properties of different contaminants can be important to helping them to adjust their risk perceptions and potentially their risk mitigation behaviors accordingly.

Effects of microbial processes on the fate of arsenic in paddy soil

Arsenic (As) is a metalloid toxic to organisms including humans. Arsenic in rice represents a significant exposure pathway for the general population, particularly for those subsisting on rice. Arsenic transformation, namely reduction, oxidation and methylation, in soil-rice systems has fundamental impacts on its mobility and toxicity. In addition to soil chemical properties (pH, Eh, metallic oxides, organic matter), microorganisms play critical roles in As transformation and mobility in paddy soil, such as through ArsM (As(III) S-adenosylmethyltransferase) and interactions with iron oxides or organic matters. Arsenic species in paddy soil directly influence As speciation in rice grain because the methylated As species in rice are mainly derived from microbial methylation in paddy soil. This paper aims to provide an overview on the status of the knowledge and gaps on the chemical aspects of As transformation in soil-rice system in conjunction with microbial ecology and functional genes. In addition, potential pathways (manipulation of microorganisms in paddy soil and genetic engineering) to decrease total As and/or inorganic As in rice grain are proposed.

Human health risks of Pb and As exposure via consumption of home garden vegetables and incidental soil and dust ingestion: A probabilistic screening tool

The consumption of home grown vegetables may represent a significant exposure pathway for arsenic (As) and lead (Pb) relative to direct incidental ingestion of soil, thus a probabilistic screening tool for estimating these exposures was developed using regression models relating co-located soil and home garden (HG) vegetable concentrations of Pb and As established from multiple independent studies and 2-dimensional Monte Carlo analyses. For high-quantity consumers of HG vegetables (i.e., the upper 95th percentile of consumers in the general population), the HG consumption pathway can be as significant as incidental soil and dust ingestion for inorganic As and, therefore, should be considered when developing generic health-based soil criteria in residential settings. Predicted Pb Hazard Quotient (HQ) estimates among young children resulting from HG consumption were 4- to 10-fold lower than exposures resulting from direct incidental soil and dust ingestion. The difference in soil/dust ingestion rates used to characterize young children (the 95th percentile of 202mg/d) versus a lifetime residential receptor (the 95th percentile of 30mg/d) was a primary factor contributing to the relative differences observed between HQ and incremental lifetime cancer risk (ILCR) resulting from these two exposure pathways for lead Pb and inorganic arsenic As, respectively.

Evaluation of Two In Vitro Protocols for Determination of Mercury Bioaccessibility: Influence of Mercury Fractionation and Soil Properties

Soil ingestion by children can be a significant exposure pathway to mercury (Hg). Unfortunately, no reliable in vivo results for Hg oral bioavailability determination in soils have been published. In vitro extractions enable the assessment of metals' bioaccessibility, which is an estimate of oral bioavailability. Therefore, the goal of this study was to evaluate two in vitro protocols (CDM (Camp Dresser and Mc Kee Inc.) and IVG (In Vitro Gastrointestinal)) for determination of Hg bioaccessibility in soils using pure Hg-compounds, reference materials (CRM 025-050 and ERM-CC580), and field-collected soils with elevated Hg concentrations. The influence of Hg fractionation and soil properties on Hg bioaccessibility was also investigated. In the field-collected soils, IVG bioaccessibility ranged from 1.5 to 7.5%, and was always below 3.15%, using the CDM method. Mercury bioaccessibility in CRM 025-050 was 61.5 and 34.7%, using IVG and CDM protocols, respectively, whereas Hg bioaccessibility was much lower in the certified sediment sample ERM-CC580 (<7%). Overall, the CDM protocol resulted in lower Hg bioaccessibility values. The water-soluble and exchangeable Hg fraction was highly correlated with gastrointestinal bioaccessibility (r=0.99, p<0.001 for both methods) and this fraction could be a potentially good indicator of Hg bioaccessibility. Because the IVG method is less time-consuming than the CDM protocol and includes organic physiological components which seem to increase Hg bioaccessibility, it might be preferred for determination of Hg bioaccessibility.

Particle size fractionation and human exposure of polybrominated diphenyl ethers in indoor dust from Chicago

The objective of this study was to investigate the concentration level, the mass distribution based on dust particle size, and the associated human exposure of polybrominated diphenyl ethers (PBDEs) in indoor dust. The total concentration of 13 PBDEs Σ13(BDEs) was found to be 500–6,944 ng/g in indoor dusts, 4,000 ng/g in car interior dust, 260–300 ng/g in outdoor ambient air particles, 30 ng/g in carpet fibers, and as high as 0.5% in carpet padding. Selected dust samples were fractionated based on particle size, and over 80% of the Σ13BDEs were associated with particles < 150 μm in diameter. Mass ratios of BDE206/BDE209 are higher in both indoor and outdoor samples than in commercial deca products; and mass ratio BDE47/BDEs(85+99+100) was much higher in outdoor than in indoor samples. Using EPA software ProUCL, the exposure of Americans to PBDEs via hand-to-mouth transfer of house dust was estimated under the central tendency exposure and reasonable maximum exposure scenarios. The results suggest that ingestion of PBDE-laden house dust via hand-to-mouth contact is likely a significant exposure pathway, especially for children.

The Health Risk Assessment of Pb and Cr leachated from fly ash monolith landfill

As of 2004, nearly two hundred thousand tons of fly ash monoliths are created each year in Taiwan to confine heavy metals for reducing the leaching quantity by precipitation. However, due to abnormal monolith fracture, poorly liner quality or exceeding usage over designed landfill capacity, serious groundwater pollution of the landfills has been reported. This research focuses on Pb and Cr leaching from monolithic landfill to assess the risk of groundwater pollution in the vicinity. The methodology combines water budget simulations using HELP model with fate and risk simulations using MMSOILS model for 5 kinds of landfill structures and 2 types of leaching models, and calculates the risk distribution over 400 grids in the down gradient direction of groundwater. The results demonstrated that the worst liner quality will cause the largest risk and the most significant exposure pathway is groundwater intake, which accounted for 98% of the total risk. Comparing Pb and Cr concentrations in the groundwater with the drinking water standards, only 14.25% of the total grids are found to be under 0.05 mg/L of Pb, and over 96.5% of the total grids are in the safety range of Cr. It indicates that Pb leaching from fly ash monolithic landfills may cause serious health risks. Without consideration of the parameters uncertainty, the cancer and noncancer risk of Pb with the sanitary landfill method was 4.23E−07 and 0.63, respectively, both under acceptable levels. However, by considering the parameters uncertainty, the non-carcinogenic risk of Pb became 1.43, exceeding the acceptable level. Only under the sealed landfill method was the hazard quotient below 1. It is important to use at least the sealed landfill for fly ash monoliths containing lead to effectively reduce health risks.