Assessment of the Dermal Bioavailability of Soil-Aged Benzo(a)pyrene

Exposure to polycyclic aromatic hydrocarbons (PAHs) in soil is a major health concern because of their mutagenic and carcinogenic properties. The aim of this research was to determine the dermal bioavailability of benzo(a)pyrene (BaP) aged in either a sandy or a clay soil in order to assess the health risks and remediation goals for the chemical. In vitro flow-through diffusion cell studies were conducted utilizing dermatomed male pig skin. The amount of radioactive chemical was measured that penetrated skin into receptor fluid and which was bound to skin following soap and water decontamination. BaP bioavailability was decreased by 95 to 98% after 3 months of aging in soil relative to the pure compound. Less than 0.3% of the dose was detected in receptor fluid for all treatments. While most of the dose was bound to skin after administering the pure compound, the majority of the radioactivity was found in the soil and decontaminate after aging. The results indicate that the health risk from exposure to BaP is significantly reduced as the compound ages in soil and that less soil cleanup would be needed at sites contaminated with aged BaP.     

Impact of Aging Time on the Dermal Penetration of Phenol in Soil

Phenol is released to soil through accidental spills, manufacturing processes, and waste disposal. With time, chemicals can become more sequestered in soil (aging). Since skin is the body's primary route of entry for phenol, the impact of aging time on the dermal penetration of phenol was assessed in Atsion and Keyport soils. In vitro studies were conducted on dermatomed male pig skin using a flow-through diffusion cell methodology and radiolabeled phenol. After 3 and 6 months of aging in the Atsion soil, dermal penetration decreased from 84% of the initial dose for pure phenol (without soil) to 15% and 8%, respectively, while the dermal penetration of phenol aged in the Keyport soil was reduced to 22% and 17%, respectively. Atsion soil has a higher organic matter content (4.4%) than Keyport soil (1.6%) suggesting that the lower bioavailability of phenol aged in the Atsion soil may be due to the amount of organic matter in that soil. Although the data indicate that the potential health risk from dermal exposure to phenol would be lower after aging in soil than to pure chemical, further experiments are warranted at lower soil loads and with additional concentrations of phenol to quantify the risk.     

Prevalence of Soil Mouthing/Ingestion among Healthy Children Aged 1 to 6

Ingestion of non-food items/mouthing behavior results in exposure of children to contaminants in soil/dust. We characterize the prevalence of such behaviors in healthy children. The relative frequency of such behaviors was assessed by parent interviews for 533 children age 1 to 6. Thirty-eight percent of children put soil in their mouths at least monthly, 24% at least weekly, and 11% daily. High-risk behavior decreased quickly for children aged 2 or more, but was still reported at least monthly by 3 to 9% of parents of children up through age 6. Highest outdoor object mouthing rates occur among 1-year-old children, who are reported to play daily in sand/dirt and have generally high levels of mouthing. Such children may have higher soil/dust ingestion and higher exposure to contaminants when soil/dust contains lead or other agents. These high-risk groups may help focus educational interventions and/or risk assessments.     

Bioavailability of Metals in Soil and Health Risk Assessment for Populations Near an Indian Chromite Mine Area

Soils contaminated with toxic metals may be environmental hazards and sources of exposure to human population. Soils in mining areas are among the most heavily contaminated by metals from the mining activity. This study was focused on metals of interest in bioavailability studies using single and sequential extraction methods. Results of geochemical fractionation suggest that changes in soil characteristics may enhance the mobilization of Cu, Cr, Zn, and Al. The observed metals’ availability pattern was Cr > Cu > Zn > Al. However, the pattern of total contents of metals in soils was Al > Cr > Zn > Cu. Risks to human adults and children from selected metals through soil ingestion was assessed in terms of incremental lifetime average daily dose (LADD), hazard quotient (HQ), and hazard index (HI). The estimated LADDs and HI were within acceptable reference doses and less than 1, respectively, indicating low risk to human populations from the studied metals through soil ingestion in the studied mine area. The generated data may be useful in remediation of contaminated soils with metals.     

A Tiered Approach for Assessing Dermal Exposure to Constituents in Latex Paint

Latex paint is commonly used by professional and consumer painters. Potential inhalation exposure to chemical vapors from paint has been studied extensively. Potential dermal exposure is not as well studied and existing exposure evaluation methods assume the paint remains wet for the duration of skin contact. However, latex paint may dry quickly and this limits the bioavailability of paint constituents due to the decreased diffusion through a dry film. This study presents a tiered in silico (i.e., computer modeling) approach to evaluate potential dermal exposure to nonvolatile substances using a technique that begins with exposure to a wet paint film and transitions to a dry film. Experiments were performed to help quantify a key parameter, latex paint drying time, and the experimental results were used in a case study to demonstrate the tiered approach. The predicted dermal penetration ranged from 100% of the applied substance for a simple conservative approach to 5% of the applied substance for the refined wet/dry film approach. Assuming the paint film was partially wiped further reduced the predicted penetration to 2%. This study addresses only latex paint but the tiered approach could be modified to evaluate other products.     

Bioavailability of Soil-borne Chemicals: A Regulatory Perspective

U.S. Environmental Protection Agency (USEPA) risk assessment guidance documents dating back to 1989 have articulated the principles for incorporating information on bioavailability into the risk assessment process. However, in the interim period both the methods for obtaining media or route specific measures of bioavailability and the corresponding guidance to incorporate these data have languished. Presently, USEPA is developing guidance to address both of these concerns. This article outlines the broad framework for systematically evaluating the role of bioavailability in site-specific risk assessment from a regulatory perspective. At the same time, in appreciation of the vast horizon of uncharted territory ahead, the focus of USEPA's draft guidance, and consequently this report, is on bioavailability adjustments for soil-borne metals. The article describes a two-stage process. The first stage outlines a paradigm for screening sites to determine if generating site-specific data on the bioavailability of a metal in soil is of technical utility and economically justifiable. The second stage focuses on the collection, analysis, and incorporation of these data into the risk assessment for decision-making purposes.     

Potential Dermal Exposure and Risk Assessment for Applicators of Chlorothalonil and Chlorpyrifos in Cucumber Greenhouses in China

Occupational exposure to pesticides has not been conducted in depth so far in China. The potential dermal exposure and risk assessment were conducted for applicators through application with a knapsack power sprayer in cucumber greenhouses. The spray suspension was prepared with 75% chlorothalonil WP and 48% chlorpyrifos EC. The dermal patch method was applied to assess the potential dermal exposure (PDE) of applicators during application. The average total PDE on the whole body of applicators during application of chlorothalonil and chlorpyrifos was 83.2 mL h^?1 and 85.1 mL h^?1, respectively. The most exposed part of the body was arms, especially the right arm. For risk assessment, the margin of safety (MOS) was calculated from the PDE. The MOS values were 0.1 and 0.2 for application of chlorothalonil and chlorpyrifos, respectively, both less than 1, which indicated low possibility of health risk.     

The Effects of Salts and Grease on BTEXs Gas/Sweat Equilibrium Partition: The Effects on Human BTEX Dermal Exposures

Human dermal exposure to volatile organic compounds (VOCs) occurs via absorption through sweat on the skin surface. Those working under hot conditions with VOCs are most susceptible. To assess dermal exposure risk to gaseous VOCs, equilibrium partitioning coefficients (p_c) at the air–sweat interface must be analyzed. This study determined the p_c values of benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene (BTEXs) in liquid concentrations of around 0.5–5 mg/l at the air–water and air–sweat interfaces at 27–47°C. The salt contents (sodium chloride, urea, ammonia, and sodium lactate) in the artificial sweat increased the p_c values of BTEXs. However, the mixture of grease (triolein and Tween 85) and salts decreased the p_c values of BTEXs. The values of p_c at 27–37°C decreased to about 21.68–60.53% for BTEXs in artificial sweat than those in pure water. The co-effect of salt and grease on p_c was elucidated further using the n-octanol-water partitioning constants (K_ow) of BTEXs. According to analytical results, the p_c of BTEXs at the air–water interfaces were larger than those for air–sweat, and the p_c data were utilized to assess risk for human dermal exposure to BTEXs.     

Risk Assessment for Dermal Exposure of Organochlorine Pesticides for Local Fishermen in the Rangsit Agricultural Area,Central Thailand

Organochlorine pesticides (OCPs) used in agriculture and for public health purposes were banned in Thailand over the past decade; however, their persistent residues have been found in several agricultural areas of the country. This may result in adverse effects to human populations. This study investigated the concentration of organochlorine pesticides residues (OCPRs) in surface water and evaluated the potential cancer risk associated with dermal contact of the local fisherman fishing in the Khlong 7 canal, Rangsit agricultural area, central Thailand. Water samples were extracted using liquid-liquid extraction (LLE) and then analyzed by gas chromatography with microelectron capture detector (μ -ECD). The results show that low concentrations of OCPRs were detected in parts per billion (ppb or ng/ml) levels, that is, ∑ Endosulfan (α -, β -, and -sulfate) 0.082 ng/ml > DDT and derivatives 0.019 ng/ml > ∑ HCH (α -, γ -, β -, and δ -HCH) 0.014 ng/ml > aldrin and dieldrin 0.007 ng/ml > heptachlor and heptachlor epoxide 0.0068 ng/ml > endrin and endrin aldehyde 0.005 ng/ml > methoxychlor 0.001 ng/ml, respectively. Using the worst-case scenario defined as the reasonable maximum exposure (RME) to assess the potential cancer risk, five OCPs (dieldrin, 4,4′ -DDT, β -HCH, heptachlor, and heptachlor epoxide) may pose a risk of concern on a lifetime human carcinogenesis greater than one in a million.     

Incorporating Information on Bioavailability of Soil-Borne Chemicals into Human Health Risk Assessments

Definition of the term bioavailability varies in the environmental sciences. In human health risk assessment, bioavailability is defined as the fraction of the dose of chemical delivered that is absorbed into the systemic circulation. Bioavailability can be expressed as either absolute or relative bioavailability, and both are important in calculating risks from contaminants in soils. Bioavailability of chemicals is addressed in all risk assessments, although not always in a transparent manner. Because data on bioavailability are limited, approximations and assumptions regarding chemical uptake are extensively used. The risk assessment process could benefit from new information on the bioavailability of chemicals, but there are important questions about the best means to develop this information and how it should be used. To foster discussion on these issues, three articles are presented in this issue of the journal offering different perspectives on bioavailability method development, validation, and use.     

An Epidemiologic Study of Arsenic-Related Skin Disorders and Skin Cancer and the Consumption of Arsenic-Contaminated Well Waters in Huhhot,Inner Mongolia,China

Well-use histories were obtained and dermatological examinations were conducted for 3,179 of the 3,228 (98.5%) residents of 3 villages in Inner Mongolia with well water arsenic levels as high as 2,000 ppb (ug/L). Eight persons were found to have skin cancer, 172 had hyperkeratoses, 121 had dyspigmentation, 94 had both hyperkeratoses and dyspigmentation, and, strikingly, none had Blackfoot disease. All 8 subjects with skin cancer also had both hyperkeratoses and dyspigmentation. Arsenic levels were measured for 184 wells and individual well-use histories were obtained. Arsenic exposure histories were summarized as both highest arsenic concentration (highest exposure level for at least 1-year duration) and cumulative arsenic exposure (ppb-years). Sixty-nine percent of the participants had highest arsenic concentrations below 100 ppb; 71% had cumulative arsenic exposures below 2,000 ppb-years. Exposure-response analyses included frequency-weighted, simple linear regression, and most-likely estimate (hockey-stick) models. Skin cancer cases were only found for those with a highest arsenic concentration greater than 150 ppb, and those with exposure less than 150 ppb had a statistically significant deficit. A frequency-weighted model showed a threshold at 150 ppb, and a hockey-stick model showed a threshold at 122 ppb. Considerations of duration, age, latency, and misclassification did not appear to markedly affect the analysis. The non-malignant skin findings showed thresholds of 40–50 ppb in the hockey-stick models. Application of these analytic models to the data from other epidemiological studies of arsenic ingestion and malignant and non-malignant skin disorders can be used to examine patterns of arsenic carcinogenicity.     

Estimation of Cd,Pb, and Zn Bioavailability in Smelter-Contaminated Soils by a Sequential Extraction Procedure

Chemical fractionation methods may be capable of providing an inexpensive estimate of contaminant bioavailability and risk in smelter-contaminated soil. In this study, the relationship between metal fractionation and methods used to estimate bioavailability of these metal contaminants in soil was evaluated. The Potentially BioAvailable Sequential Extraction (PBASE) was used for Cd, Pb, and Zn fractionation in 12 soils contaminated from Pb and Zn mining and smelting activities. The PBASE procedure is a four-step sequential extraction: extraction 1 (E1) is 0.5 M Ca(NO₃)₂, E2 is 1.0 M NaOAc, E3 is 0.1 M Na₂EDTA, and E4 is 4 M HNO₃. Metal bioavailability for two human exposure pathways, plant uptake (phytoavailability) and incidental ingestion (gastrointestinal, Gl, availability), was estimated using a lettuce (Lactuca sativa L.) bioassay and the in vitro-Gl Physiologically Based Extraction Test(PBET). Metal in the PBASE E1 fraction was correlated with lettuce Cd (P < 0.001) and Zn (P < 0.05) and was the best predictor of Cd and Zn phytoavailability. Only total metal content or the sum of all PBASE fractions, ΣE_1–4, were correlated (P < 0.001) with PBET gastric phase for Pb. The sum of the first two PBASE fractions, ΣE_1–2, was strongly correlated (P < 0.001) with Pb extracted by the PBET intestinal phase. The PBASE extraction method can provide information on Cd and Zn phytoavailability and Gl availability of Pb in smelter-contaminated soils.     

Protective Effect of Detoxified Rhus verniciflua Stokes on Human Keratinocytes and Dermal Fibroblasts against Oxidative Stress and Identification of the Bioactive Phenolics

Oxidative stress due to the over-production of reactive oxygen species (ROS) is associated with human skin aging. This study was designed to identify the bioactive phenolics in detoxified Rhus verniciflua Stokes (DRVS) that may protect human skin against oxidative stress. Under oxidative stress caused by H₂O₂, the 40% (v/v) aqueous methanol extract of DRVS protected human keratinocytes in a dose-dependent manner. The expression of matrix metalloproteinase-1 (MMP-1) was also inhibited by the DRVS extract in human dermal fibroblasts-neonatal cells exposed to ultraviolet A. The major bioactive phenolics of DRVS were tentatively identified by LC/Q-TOF-ESI-MS/MS, and included gallic acid, 2-(ethoxymethoxy)-3-hydroxyphenol, fustin, a fustin isomer, tetragalloyl glucose, pentagalloyl glucose, fisetin, sulfuretin, a sulfuretin isomer, and butein. The results suggest that a DRVS extract may be effective in slowing skin aging through its antioxidative properties and by down-regulating MMP-1 expression. Further studies are needed to examine whether this effect would be mediated by the phenolics identified in this study.     

Overview of Toxicity Data and Risk Assessment Methods for Evaluating the Chemical Effects of Depleted Uranium Compounds

In the United States, depleted uranium is handled or used in several chemical forms by both governmental agencies and private industry (primarily companies producing and machining depleted uranium metal for military applications). Human exposure can occur as a result of handling these compounds, routine low-level effluent releases to the environment from processing facilities, or materials being accidentally released from storage locations or during processing or transportation. Exposure to uranium can result in both chemical and radiological toxicity, but in most instances chemical toxicity is of greater concern. This article discusses the chemical toxic effects from human exposure to depleted uranium compounds that are likely to be handled during the long-term management and use of depleted uranium hexafluoride (UF₆) inventories in the United States. It also reviews representative publications in the toxicological literature to establish appropriate reference values for risk assessments. Methods are described for evaluating chemical toxicity caused by chronic low-level exposure and acute exposure. Example risk evaluations are provided for illustration. Preliminary results indicate that chemical effects of chronic exposure to uranium compounds under normal operating conditions would be negligibly small. Results also show that acute exposures under certain accident conditions could cause adverse chemical effects among the populations exposed.     

Investigation of Dermal Contact with Soil in Controlled Trials

A series of laboratory, greenhouse, and field experiments have been conducted at the University of Washington to improve the empirical grounding of dermal/soil pathway risk calculations. This article presents results from controlled trials, conducted in a greenhouse, in which volunteers engaged in activities in soil amended with a fluorescent marker. Activities included transplanting of bedding plants and laying of pipe by adults and children's play. Soil contact on hands, forearms, lower legs, and faces was examined using both fluoro-metric and gravimetric measurements. Results provide information on pre- and postactivity loadings, the extent of contact associated with the selected activities, and the effects of clothing, activity duration, and soil moisture. Preactivity loadings were consistent with previously reported observations. Following activity, skin coverage was found to be substantially incomplete except on hands. Local soil loadings may therefore deviate markedly from mean values obtained by washing skin surfaces. A protective effect of clothing was observed but may reflect the relatively short duration of the experiments and the use of freshly laundered clothing. No significant trend in soil loading with exposure duration was found, although some evidence of increasing surface area involvement with time was observed. Finally, wet soil activities produced consistently higher loadings on volunteers' hands than dry soil activities.     

The Changing Focus of the Ecological Risk Assessment of Aquaculture Operations: From Local to Cumulative Risk Assessment

Ecological risk assessment (ERA) methodologies must be continually improved so that resource managers, activity proponents, and stakeholders can better manage the environmental impacts of human activities. One of the largest challenges facing ERA methodologies and approaches is to develop the ability to encompass cumulative and far-field effects of human activities. It is argued here that the ERAs of industrial aquaculture activities have been an example of where ERA practitioners and researchers have responded to the challenge of managing the cumulative risks of a new and rapidly growing industry by developing innovative ERA approaches that can be applied elsewhere.     

Health risk assessment of volatile organic compounds in urban areas

The atmosphere is the first medium containing hazardous compounds entering the living environment. Metropolitan areas contain many industrial complex areas with high emissions of volatile organic compounds (VOCs), and consequently also large-scale exposure groups. As respiration is the most important part of the human exposure pathway, the atmosphere should be treated with greater importance than other media. It is therefore very important to monitor the emission of hazardous air pollutants (HAPs) and measure the concentration of VOCs in the atmosphere of such areas. It is essential to establish basic measures in order to protect public health as part of overall national safety management. This study utilized the national air pollution monitoring network data from Seoul, Incheon, and Gyeonggi, and investigated the differences in risk levels for humans considering various factors of the receptors, including gender and age. A total of 13 VOCs were categorized into carcinogens and noncarcinogens for risk assessment. The carcinogens 1,3-butadiene and benzene demonstrated a high level of cancer risk, ranging between 10^?4 and 10^?6, respectively. Noncarcinogens did not exceed Hazard Quotient (HQ) 1 in any area. The results will serve as important references for managing urban air environments and setting air quality standards.     

Health Risks of Metals in Soil,Water, and Major Food Crops in Hamedan Province,Iran

Food, drinking water, soil, and air are the main routes of exposure to trace metals, thus the assessment of the risks posed to humans by these elements is important. Wheat, potatoes, and maize are very important parts of the Iranian diet. The objectives of this study were to estimate the non-carcinogenic and carcinogenic health risks of Hg, Pb, Cd, Cr, Se, As, and Ni to adults and children via soil, water, and major food crops consumed in Hamedan Province, northwest Iran, using the total non-cancer hazard quotient (THQ) and cancer risk assessment estimates. Total non-cancer hazard of Ni and Hg, were greater than 1, and total cancer risk of As and Pb was greater than 1 × 10^?6. Food consumption was identified as the major route of human exposure to metals, and consuming foodstuff threatens the health of the studied population. In Hamedan Province, consumption of wheat is the main source of intake of metals from foodstuff for adults, and in children, the soil ingestion route is also important.     

Soil ingestion rates in children identified by parental observation as likely high soil ingesters

Soil ingestion was estimated over seven consecutive days in a soil tracer‐based mass‐balance methodology in 12 children, aged 1 to 3 years. The children had been identified by parents as likely high soil ingesters based on retrospective observation of daily soil ingestion behavior over the past 30 d. While one of the 12 children displayed high soil ingestion (0.5 to 3.05 g/d) on 4 of 7 d, median soil ingestion rates for the 12 children were comparable to those published in other soil ingestion studies of young children selected for studies based on age and not assumed or observed soil ingestion behavior. The lack of ability of parental judgments to predict high soil ingestion rates represents both an important observation and a significant limitation in current methods to efficiently and accurately identify children who ingest high amounts of soil.