Abstract  When studying the density of skin lesions, calculations of relative density are based on charts of proportion of skin surface area. However, the current source of information is derived from skewed data obtained at the beginning of the twentieth century. Using more recent data from a population-based sample of children in the United States, we propose a new set of tables. Data from measurements taken in the United States in the 1970s for design and safety were applied to the computer-based model MAN3D. This model, originally created for ergonomic studies in the automotive industry, allowed us to obtain a precise estimate of the main surface areas of children. Compared with previously published studies, our estimates increased the relative proportion of arms and of the trunk and allowed for differentiation of these proportions by sex. New tables are proposed for epidemiological studies of skin lesion density in children.

Abstract  Dermal contact with sediment is sometimes identified as a pathway of concern in risk assessments. Dermal exposure to sediment is poorly characterized and exposure assessors may rely on default soil adherence values. The purpose of this study was to obtain sediment adherence data for a genuine exposure scenario, child play in a tide flat. This study reports direct measurements of sediment loadings on five body parts (face, forearms, hands, lower legs and feet) after play in a tide flat. Each of nine subjects participated in two timed sessions and pre- and post-activity sediment loading data were collected. Geometric mean (geometric standard deviation) dermal loadings (mg/cm(2)) on the face, forearm, hands, lower legs and feet for the combined sessions were 0.04 (2.9), 0.17 (3.1), 0.49 (8.2), 0.70 (3.6) and 21 (1.9), respectively. Participants' parents completed questionnaires regarding their child's typical activity patterns during tide flat play, exposure frequency and duration, clothing choices, bathing practices and clothes laundering. Data presented in this paper supplement very limited prior adherence data for sediment contact scenarios. Results will be useful to risk assessors considering exposure scenarios involving child activities at a coastal shoreline or tide flat.

Abstract  Sediment contamination is common and assessment of potential dermal exposure to sediments is of interest to risk assessors. However, few measurements of coastal sediment (as opposed to terrestrial soil) adherence to skin have been reported in the literature. Results are reported here for sediment loads on the skin of 18 adults engaged in clam digging for periods of up to 90 minutes in a tide flat in Rhode Island. Post-activity geometric mean loads were 0.02, 0.12, 0.16, 0.58 and 0.88 mg/cm2 on faces, forearms, lower legs, feet and hands, respectively. Pre-activity loadings were less than 0.01 mg/cm2 on all body parts except feet. These results are similar to very limited previously reported data obtained from four persons gathering reeds for basketry in a tide flat in Washington State.

Abstract  Impact/Purpose: The goal of this task is to contribute to a better understanding of human exposure to pesticides, especially for small children by developing methods to characterize sources and pathways in and around the residential environment. We will support the science behind FQPA and assist the Office of Pesticide Programs (OPP) in the development of guidelines for the assessment of residential exposure to pesticides. Specific research objectives include: (i) to evaluate and develop methods for measuring pesticides in air using passive/diffusive samplers. Assess and refine devices for the collection of surface transferable pesticide residues and to establish transfer efficiencies; (ii) to develop and apply analytical methods for new and emerging pesticides using both gas and liquid chromatographic methods in support of the National Exposure Research Laboratory's (NERL) Human Exposure Measurement Project; and, (iii) to conduct pilot studies investigating chiral chromatographic methods. Description: This report presents results of a study to determine the distribution of pesticides, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) between dust and carpet components in aged carpeting. Carpeting in eight homes in the Research Triangle Area, which were recruited on the bases of carpet age . In each household, two 1 m2 areas, one high-traffic and one low-traffic, were selected for sampling prior to carpet replacement. Each area was first subjected to sampling with the PUF Roller to determine dislodgeable residues, then sequentially vacuumed with the HVS3 and Hoover Deep-dust vacuum systems and the collected dust samples separately analyzed. Subsequently, the carpet areas were excised and the pile removed from the backing for separate extraction and analysis. The carpet pad under the sampled areas was likewise extracted and analyzed, as was dust collected from the flooring beneath the pad. Analyses of all samples for 39 neutral-extractable pesticides, PAHs and PCBs revealed that the major portions of the pollutants were within the carpet fibers, backing and pad. The work reported in this document was performed for the Exposure Methods and Monitoring Branch, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC, during the period July 1997 to April 1999 under Work Assignments 47 and 76 of Contract 68-5-0049 by ManTech Environmental Technology, Inc., and by Southwest Research Institute under Subcontract 96-0049-01 to ManTech. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.

Abstract  A computer-controlled mechanical chamber was used to control the contact between carpet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. Mass soil transfers were converted to adherence factors (mg/cm(2)) for use in models that estimate dermal exposure to contaminants found in soil media. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 sec) were varied for 369 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 mu m and >= 139.7 < 381) were used. Chamber probes were used to record temperature and humidity. Log transformation of the sand/soil transfers was performed to normalize the distribution. Estimated adjusted means for experimental conditions were exponentiated in order to express them in the original units. Mean soil mass transfer to cadaver skin (0.74 mg/cm(2)) was higher than to cotton sheets (0.21 mg/cm(2)). Higher pressure (p < 0.0001), and larger particle size (p < 0.0001) were also all associated with larger amounts of soil transfer. The original model was simplified into two by adherence material type (i.e., cadaver skin and cotton sheets) in order to investigate the differential effects of pressure, time, soil size, and soil type on transfer. This research can be used to improve estimates of dermal exposure to contaminants found in home carpets.

Abstract  The Office of Research and Development of the U.S. EPA has completed a guidance document entitled: "Dermal Exposure Assessment: Principles and Applications" to provide the principles of dermal absorption and outline procedures on how to apply these principles to actual dermal exposure scenarios including water, air and soil exposures. For all three media, experimental values of dermal absorption constants of environmental pollutants are summarized from the literature. Where data is lacking, predictive structure-activity correlations are recommended for pollutants in aqueous media and in air. For dermal exposure to soil, several approaches are suggested for evaluation.

Abstract  The lead content of air, house dust, dirt, dirt on hands, food, and water was investigated in order to ascertain the cause of the chronically elevated blood lead levels in ten 2–6 year old Hartford children. Recent ingestion of leaded paint had been eliminated as a significant factor. The mean ambient air levels at 2 and 5 ft. from the ground where the children played varied from 1.7–7 μg/m3. On the basis of “mouthing” behavior observed among the ten subject children, the mean lead levels in dirt (1200) μg/g) and dust (11,000 μg/g) and the mean lead concentration of lead on hands (2400) μg/g), it is likely that the “hands in mouth” exposure route is the principal cause of the excessive lead accumulation in these children.

Abstract  The California Site Mitigation Decision Tree Manual, 1985, was developed by the California Department of Health Services to provide a detailed technical basis for managing uncontrolled hazardous waste sites. The Decision Tree describes a process that relies on criteria, Applied Action Levels (AALs) to evaluate and, if necessary, mitigate the impact of uncontrolled hazardous waste sites on the public health and the environment. AALs are developed for individual substances, species, and media of exposure. AALs have been routinely developed for the media of air and water; however, an approach for developing AALs for soil contact was lacking. Given that the air pathway for soil contact is addressed in AALs for air, two routes of exposure, ingestion and dermal contact, are addressed in developing AALs for soil contact. The approach assumes a lifetime of exposure to soil in a residential setting. Age-related changes in exposure are included in the scenario. Exposure to soil due to ingestion and dermal contact are quantitated independently and then integrated in the final exposure scenario. A mass balance approach using four elements is employed to quantitate soil ingestion for a young child. Changes in soil ingestion with age are based on age-related changes in blood lead concentration and mouthing behavior. Dermal exposure to soil was determined from studies that reported skin soil load and from estimates of exposed skin surface area. Age-related changes in the dermal exposure to soil are also based on changes with age of blood lead concentration and mouthing behavior. The estimates of exposure to soil due to ingestion and dermal contact are integrated, and an approach for developing AALs is advanced. AALs are derived by allocating the Maximum Exposure Level as described in the Decision Tree to the average daily exposure to soil. Toxicokinetic considerations for the two routes of exposure must be included in deriving AALs for the soil medium of exposure.

Abstract  The U.S. Environmental Protection Agency (EPA) developed Risk Assessment Guidance for Superfund: Volume I Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) ("Part E") to address human health risk related to dermal exposures. Parts A, B, C and D of RAGS address other aspects of a human health risk assessment on a Superfund site. Part E uses a consistent methodology for assessing the exposures from the dermal pathway for Superfund human health risk assessments. It incorporates and updates principles of the EPA (1992) interim report, "Dermal Exposure Assessment: Principles and Applications". Part E does not address dermal exposure to vapors.

Abstract  NIOSH abstract: Laboratory studies on the effects of soil particle size and moisture content on soil adherence were conducted to quantify soil load, as a risk factor in skin contact with soil contaminants. Five locally obtained soils were characterized for testing. Hand press trials were done by placing a hand palm down in a pan of soil and gently agitating for 30 seconds. Hands were washed in 2% detergent, with a 4 liter garden sprayer providing water pressure. Wash water was filtered with 47 millimeter glass fiber filters with a 0.5 micrometer (microm) pore size. Filters were oven dried overnight, at 100 degrees-C, in tared aluminum weigh boats and cooled in a desiccator prior to weighing. Adherence and post adherence tests were performed on soils fractionated by size, through dry sieving, for 30 minutes. Comparisons were made with the Mannhitney U-test and t-tests. Adherence of dry soil, defined as less than 2% moisture, varied inversely with particle size and soil specific differences were significant by Mann/Whitney test (two tailed p-values less than 0.05) and for all but one case by t-test. Adherence of wet soils (12 to 18% moisture) varied directly with size. Within three of the five soils, paired differences between size fractions were significant by Mann/Whitney test and in all but one case by t-test. The differences between wet and dry samples, within size fractions, showed that most wet soils showed significantly greater adherence for larger particle sizes (greater than 150microm). The authors conclude that larger particle sizes are relevant in assessing exposure to contaminants when soil moisture exceeds 10%. In soils with less than 10% moisture content, particles less than 150microm in diameter are primarily responsible for adherence.

Abstract  Many dermal exposure models use stochastic techniques to sample parameter distributions derived from experimental data to more accurately represent variability and uncertainty. Transfer efficiencies represent the fraction of a surface contaminant transferred from the surface to the skin during a contact event. Although an important parameter for assessing dermal exposure, examination of the literature confirms that no single study is large enough to provide a basis for a transfer efficiency distribution for use in stochastic dermal exposure models. It is therefore necessary to combine data sets from multiple studies to achieve the largest data set possible for distribution analysis. A literature review was conducted to identify publications reporting transfer efficiencies. Data sets were compared using the Kruskal-Wallis test to determine whether they arise from the same distribution. Combined data were evaluated for several theoretical distributions using the Kolmogorov-Smirnov and chi(2)-goodness-of-fit tests. Our literature review identified 35 studies comprising 25 different sampling methods, 25 chemicals, and 10 surface types. Distributions were developed for three different chemicals (chlorpyrifos, pyrethrin I, and piperonyl butoxide) on three different surface types (carpet, vinyl, and foil). Only the lognormal distribution was consistently accepted for each chemical and surface combination. Fitted distributions were significantly different (Kruskal-Wallis test; P<0.001) across chemicals and surface types. In future studies, increased effort should be placed on developing large studies, which more accurately represent transfer to human skin from surfaces, and on developing a normative transfer efficiency measure so that data from different methodologies can be compared.

Abstract  Stratum corneum thickness was estimated from water concentration profiles of the skin measured by a confocal Raman spectrometer. Stratum corneum apparent thickness (SCAT) was defined as the depth where the water content reached an almost constant value. Site variations were determined using 15 healthy Japanese subjects (6 males, 9 females), and age variations at the cheek and forearm were examined using 27 female Japanese subjects. There were marked site variations in mean SCAT; 16.8 microm for cheek, 22.6 microm for volar forearm, 29.3 microm for back of the hand, and 173.0 microm for palm. These variations were similar to reported stratum corneum thickness values obtained in biopsy tissues. The SCAT tended to become age-dependently thicker at the forearm, but not at the cheek. In addition, SCAT was increased up to two-fold by hydration for 90 min, while lesser increases were seen with shorter hydration periods.

Abstract  A handwipe sampling and analysis procedure was developed for the measurement of dermal contact to pesticides. This procedure utilizes cellulose dressing sponges wetted with 2-propanol. A two-step wiping procedure is described that ensures that the entire hand is sampled. Removal efficiency experiments show that dry residues of the pesticides chlorpyrifos and pyrethrin I are quantitatively removed from hands immediately following contact. Results suggest that the procedure may remove pesticide residues that are deeply embedded in the skin and not removed by soap-and-water washing. Extraction efficiency studies for 29 other pesticides show that the proposed extraction method may be applicable for a wide range of pesticides including phenoxy-acid herbicides. Field testing of the procedure indicates that it is easily implemented by sampling personnel and readily accepted by children.

Abstract  Despite its heterogeneity, stratum corneum (SC) has been described as a homogeneous membrane for water diffusion. We measured water flux across the SC, transepidermal water loss (TEWL), in six women, in vivo. At four anatomical sites--back, abdomen, forearm, and thigh--we took measurements during sequential tape stripping. The inverse of TEWL (1/TEWL) and removed SC thickness yielded a highly linear correlation (Pearson's r ranging between 0.88 and 0.99). Applying Fick's law of diffusion, we calculated SC thickness (H), and SC water diffusion coefficient (D). Comparing the results, SC of all women was significantly thicker (p < 0.05) at the extremities (12.7 +/- 4.2 microm, mean +/- SD, n = 12) than the abdomen (7.7 +/- 1.8 microm, n = 6). The calculated diffusion coefficient approximated 2.16 +/- 1.14x10(-9) cm2/s. Compared with the diffusion constant found for SC depleted of lipids, our value was 100-fold lower. In agreement with previous findings that intercellular lipids are a rate determining component of the SC barrier, we suggest that water diffuses mainly through the intercellular space. The calculation of H and/or D, however, is based on several variables: SC density, the water concentration difference, and the partition coefficient of water between viable epidermis and SC. The literature values vary widely. It is desirable to determine these parameters more precisely, especially if discrete differences, such as between anatomical sites, are to be revealed.

Abstract  It has recently been suggested that “standard” data distributions for key exposure variables should be developed wherever appropriate for use in probabilistic or “Monte Carlo” exposure analyses. Soil‐on‐skin adherence estimates represent an ideal candidate for development of a standard data distribution: There are several readily available studies which offer a consistent pattern of reported results, and more importantly, soil adherence to skin is likely to vary little from site‐to‐site. In this paper, we thoroughly review each of the published soil adherence studies with respect to study design, sampling, and analytical methods, and level of confidence in the reported results. Based on these studies, probability density functions (PDF) of soil adherence values were examined for different age groups and different sampling techniques. The soil adherence PDF developed from adult data was found to resemble closely the soil adherence PDF based on child data in terms of both central tendency (mean = 0.49 and 0.63 mg‐soil/cm2‐skin, respectively) and 95th percentile values (1.6 and 2.4 mg‐soil/cm2‐skin, respectively). Accordingly, a single, “standard” PDF is presented based on all data collected for all age groups. This standard PDF is lognormally distributed; the arithmetic mean and standard deviation are 0.52 ± 0.9 mg‐soil/cm2‐skin. Since our review of the literature indicates that soil adherence under environmental conditions will be minimally influenced by age, sex, soil type, or particle size, this PDF should be considered applicable to all settings. The 50th and 95th percentile values of the standard PDF (0.25 and 1.7 mg‐soil/cm2‐skin, respectively) are very similar to recent U.S. EPA estimates of “average” and “upper‐bound” soil adherence (0.2 and 1.0 mg‐soil/cm2‐skin, respectively).

Abstract  Homeowners and professional applicators frequently use chemicals to control insect pests in urban environments. The identification and evaluation of determinants of human exposure are critical to conduct reliable and responsible human exposure assessments following indoor residential chemical applications. The effect of sweat on absorbed dose in humans was evaluated with human volunteers who participated in a structured activity program (SAP). Participants (n=20) performed a warm-up exercise to induce light sweating prior to an SAP on chlorpyrifos(cp)-treated nylon carpet. Absorbed daily dosages (ADDs) were calculated using urinary biomonitoring of trichloropyridinol. In two separate exposures, participation in the warm-up exercise prior to the exposure SAP resulted in an increased ADD of CP equivalents by approximately 50%. Measured ADDs averaged 2.8 (SAP 1) and 2.0 (SAP 2) microg CP equivalents/kg/day in volunteers who participated in the warm-up exercise. In participants who rested prior to the exposures, ADDs were significantly lower at 1.9 (SAP 1) and 1.3 (SAP 2) microg CP equivalents/kg/day. Perspiration may also be a determinant of exposure in active children and field workers. Measured ADDs were less than estimates of ADD made from environmental measurements including CP deposition, the California roller, and clothing dosimeters worn by participants.

Abstract  Protocols used to assess human exposure to chemicals in soils at contaminated sites often include a dermal pathway. Use of default parameters to assess dermal exposure to soil can easily lead to risk projections that appear to warrant remedial action. However, because those default parameters are typically highly uncertain, risk estimates based upon them inspire little confidence. To better characterize assumptions regarding dermal exposures, a telephone survey instrument was developed to elicit information on behaviors relevant to assessment of dermal contact with soil and dust. Participation in four activities--gardening, other yard work, outdoor team sports, and home construction or repair involving digging--was investigated. Questions were also asked regarding clothing choices and post-activity bathing practices. The survey was administered to two populations of approximately 450 adult respondents each using random digit dialing. The first was a national (U.S.) sample. The second sample was drawn from counties surrounding the Hanford Nuclear Reservation. Seventy-nine percent of the regional respondents and 89% of the national respondents reported participating in at least one of the four targeted activities. Responses of doers regarding clothing choices suggest that median fractions of skin exposed during warm-weather activities typically exceed the 25% often assumed. The Hanford sample differed from the national sample in the fraction residing in single-family homes, the fraction describing their residential surroundings as rural, and in ethnic makeup. The Hanford population displayed greater rates of participation than the national sample in three activities that have an obvious link to residence in a single-family dwelling: home repair involving digging, gardening, and other yard work, but differences were not explained entirely by residence type. The regional population also reported greater frequency of participation in multiple activities. In contrast, clothing choices among doers could not be distinguished between the two groups.

Abstract  Estimates of soil adherence to skin are required for assessment of dermal exposures to contaminants in soils. Previously available estimates depend heavily on indirect measurements and/or artificial activities and reflect sampling of hands only. Results are presented here from direct measurement of soil loading on skin surfaces of volunteers before and after normal occupational and recreational activities that might reasonably be expected to lead to soil contact. Skin surfaces assayed included hands, forearms, lower legs, faces and/or feet. Observed hand loadings vary over five orders of magnitude (roughly from 10(-3) to 10(2) mg/cm2) and are dependent upon type of activity. Hand loadings within the current default range of 0.2 to 1.0 mg/cm2 were produced by activities providing opportunity for relatively vigorous soil contact (rugby, farming). Loadings less than 0.2 mg/cm2 were found on hands following activities presenting less opportunity for direct soil contact (soccer, professional grounds maintenance) and on other body parts under many conditions. The default range does not, however, represent a worst case. Children playing in mud on the shore of a lake generated geometric mean loadings well in excess of 1 mg/cm2 on hands, arms, legs, and feet. Post-activity average loadings on hands were typically higher than average loadings on other body parts resulting from the same activity. Hand data from limited activities cannot, however, be used to conservatively predict loadings that might occur on other body surfaces without regard to activity since non-hand loadings attributable to higher contact activities exceeded hand loadings resulting from lower contact activities. Differences between pre- and post-activity loadings also demonstrate that dermal contact with soil is episodic. Typical background (pre-activity) geometric mean loadings appear to be on the order of 10(-2) mg/cm2 or less. Because exposures are activity dependent, quantification of dermal exposure to soil will remain inadequate until data describing relevant human behavior (type of activity, frequency, duration including interval before bathing, clothing worn, etc.) are generated.

Abstract  The size distributions of the soil particles adhered to children's hands were preliminarily investigated and compared with a cutoff soil particle size recently specified in the official analytical method in Japan. To facilitate fieldworks involving child participants, we tested a methodology using a laser scattering particle size distribution analyzer and validated it for field applications. The laboratory experiments using this method showed finer soil particles tended to be adhered more efficiently to human hands. Meanwhile, our preliminary field survey revealed large variations in mass (mean 26.2 mg/hand, median 15.2 mg/hand, max 162.5 mg/hand) and size distributions (particle mode diameter of 39 +/- 26 mu m) of the particles adhered to children's hands after various playing activities. Even though the ways the particles adhered were noticeably varied under actual playing situations, the adhered particles were consistently and considerably smaller than the 2-mm cutoff diameter defined by the Ministry of the Environment, Japan. Since soil contaminant concentrations are generally higher for finer soil particles, measurement of contaminant concentrations for the soil fraction including the non-adherent millimeter particles may underestimate the risk of direct soil contaminant intakes.