Spatial distributions of arsenic exposure and mining communities from NHEXAS Arizona. National Human Exposure Assessment Survey.

Within the context of the National Human Exposure Assessment Survey (NHEXAS), metals were evaluated in the air, soil, dust, water, food, beverages, and urine of a single respondent. Potential doses were calculated for five metals including arsenic. In this paper, we seek to validate the potential dose calculations through spatial analysis of the data. Others report elevated arsenic concentrations in biological and environmental samples from residents of mining towns, particularly Ajo, Arizona. These reports led us to expect potential arsenic doses above the 90th percentile of the NHEXAS exposure distribution to be from residents of mining communities. Arsenic dose was calculated using media concentrations, time activity patterns, and published exposure factors. Of the 179 homes evaluated, 54 were in mining communities; 11 of these were considered separately for reasons of population bias. Of the 17 homes with the greatest potential arsenic doses, almost half (47%) were in mining communities. We evaluated the potential doses by media from nonmining and mining areas using the nonparametric Mann-Whitney U test. Statistically significant (p = 0.05) differences were found between mining (n = 43) and nonmining sites (n = 122) for total exposure and for each of the following media: house dust, yard soil, outdoor air, beverage consumed, and water consumed. No differences were found in either food or indoor air of mining and nonmining areas. We eliminated outliers and repeated the test for all media; significance increased. Dietary, organic arsenic from fish consumption contributed to elevated arsenic exposure among people from nonmining communities and acted as an initial confounder. When controlling for fish consumption, we were able to validate our potential dose model using arsenic, particularly in Ajo. Further, we identified three mining communities lacking elevated arsenic exposure. Additional work is needed speciating the arsenic and evaluating health risks. The utilization of Geographic Information System facilitated spatial this project and paves the way for more sophisticated future spatial analyses.     

Contributions of inhalation and dermal exposure to chlorpyrifos dose in Egyptian cotton field workers

Abstract

Objective: Chlorpyrifos exposures were assessed in 12 Egyptian cotton field workers.

Methods: 3,5,6-trichloro-2-pyridinol (TCPy) was measured in 24-hour urine samples to estimate absorbed dose. Workshift air samples were used to calculate chlorpyrifos inhalation dose.

Results: Patches on legs had the highest chlorpyrifos loading rates among body regions sampled. Geometric mean chlorpyrifos air concentrations were 5·1, 8·2, and 45·0 μg/m³ for engineers, technicians, and applicators, respectively; peak TCPy urinary concentrations were 75–129, 78–261, and 487–1659 μg/l, respectively; geometric mean doses were 5·2–5·4, 8·6–9·7, and 50–57 μg/kg, respectively, considering TCPy excretion half-life values of 27 and 41 hours. All worker doses exceeded the acceptable operator exposure level of 1·5 μg/kg/day. An estimated 94–96% of the dose was attributed to dermal exposure, calculated as the difference between total dose and inhalation dose.

Discussion: Interventions to reduce dermal exposure are warranted in this population, particularly for the hands, feet, and legs.     

Assessment of human exposure to copper: a case study using the NHEXAS database

Copper is an essential trace element and adverse health effects can potentially be associated with both very low and very high intakes. Accurate estimates of inhalation and ingestion (food and drinking water) exposures are therefore needed in order to realistically assess any effects of the distribution of copper intakes within the general population. The work presented here demonstrates an application of a customized subset of the MENTOR/SHEDS-4M computational system (Modeling ENvironment for TOtal Risk studies, employing the Stochastic Human Exposure and Dose Simulation approach, for Multimedia, Multipathway, Multiroute exposures to Multiple co-occurring contaminants. The application utilized data from the National Human Exposure Assessment Survey (NHEXAS) for USEPA Region V as well as from a variety of other available databases. The case study, using a statistical population-based modeling framework, was performed for Eaton County, MI. The results of the simulations, aggregated for six age subgroups of the general population, suggest that food intake is the major pathway for total copper exposure, while drinking water can have significant contributions at the tail of the distribution of intakes. Specifically, it was estimated that over 80% of the county population received potential doses of copper from food that were lower than the Institute of Medicine (IOM) Recommended Dietary Allowance (RDA) value of 900 microg/day. Furthermore, the total combined potential dose from food and water was only about two times greater than the recommended value only for individuals with intakes in the range above the 99th percentile of both food and water intakes. The values were well below the upper tolerable intake value of 10,000 microg/day. The inhalation route consistently acted as only a minor contributor to the total exposure.     

A modeling framework for estimating children's residential exposure and dose to chlorpyrifos via dermal residue contact and nondietary ingestion

To help address the Food Quality Protection Act of 1996, a physically based probabilistic model has been developed to quantify and analyze dermal and nondietary ingestion exposure and dose to pesticides. The Residential Stochastic Human Exposure and Dose Simulation Model for Pesticides (Residential-SHEDS) simulates the exposures and doses of children contacting residues on surfaces in treated residences and on turf in treated residential yards. The simulations combine sequential time-location-activity information from children's diaries with microlevel videotaped activity data, probability distributions of measured surface residues and exposure factors, and pharmacokinetic rate constants. Model outputs include individual profiles and population statistics for daily dermal loading, mass in the blood compartment, ingested residue via nondietary objects, and mass of eliminated metabolite, as well as contributions from various routes, pathways, and media. To illustrate the capabilities of the model framework, we applied Residential-SHEDS to estimate children's residential exposure and dose to chlorpyrifos for 12 exposure scenarios: 2 age groups (0-4 and 5-9 years); 2 indoor pesticide application methods (broadcast and crack and crevice); and 3 postindoor application time periods (< 1, 1-7, and 8-30 days). Independent residential turf applications (liquid or granular) were included in each of these scenarios. Despite the current data limitations and model assumptions, the case study predicts exposure and dose estimates that compare well to measurements in the published literature, and provides insights to the relative importance of exposure scenarios and pathways.     

Evaluations of primary metals from NHEXAS Arizona: distributions and preliminary exposures. National Human Exposure Assessment Survey.

NHEXAS AZ is a multimedia, multipathway exposure assessment survey designed to evaluate metals and other analytes. This paper reports the analyte-specific concentration distributions in each of the media examined (air, soil, house dust, food, beverage, and water), for various methodologies used (inductively coupled plasma-atomic emission spectroscopy and hydride generation-atomic absorption spectroscopy). Results are reported for the five primary metals (Pb, As, Cd, Cr, and Ni). Ingestion was the most important pathway of exposure. Metal concentrations in air were very low (ng/m3) and found only above the 90th percentile. Metals were commonly found in house dust and soil. Exposure transfer coefficients minimize the importance of this component for those over the age of 6 years. When ranked by exposure, food, beverage, and water appeared to be the primary contributors of metal exposure in NHEXAS AZ. For instance, at the 90th percentile, Pb was undetected in air, found at 131 and 118 microg/m3 in floor dust and soil, respectively, and measured at 16 microg/kg in food, 7.1 microg/kg in beverage, and 2.0 and 1.3 microg/l in drinking and tap water, respectively. We calculated preliminary estimates of total exposure (microg/day) for each participant and examined them independently by age, gender, and ethnicity as reported by the subjects in the NHEXAS questionnaire. At the 90th percentile for Pb, total exposures were 64 microg/day across all subjects (n=176); adult men (n=55) had the greatest exposure (73 microg/day) and children (n=35) the least (37 microg/day). Hispanics (n=54) had greater exposure to Pb (68 microg/day) than non-Hispanics (n=119; 50 microg/day), whereas non-Hispanics had greater exposure for all other metals reported. These results have implications related to environmental justice. The NHEXAS project provides information to make informed decisions for protecting and promoting appropriate public health policy.     

Improving cancer incidence estimates for American Indians in Minnesota.

OBJECTIVES: The purpose of this study was to estimate cancer incidence for American Indians in Minnesota. METHODS: Indian Health Service enrollment data were linked to the Minnesota tumor registry to identify cancers among American Indians in Minnesota. Incidence rates for the 5 most common cancers in this population, estimated after the linkage, were compared with rates estimated before the linkage and with rates for the total population of Minnesota. RESULTS: The linkage identified 302 cancer cases not previously identified as occurring among American Indians in Minnesota. Postlinkage estimates suggested that incidence rates for prostate and colorectal cancer are similar to those for the total population of Minnesota, but that rates of lung and cervical cancer are significantly higher. Breast cancer rates are slightly lower than those for the total population of Minnesota but more than twice as high as previous estimates for American Indians. CONCLUSIONS: The postlinkage estimates suggest different priorities for cancer education, prevention, and control than might be assumed from either prelinkage estimates or previously published data, and underscore the importance of using accurate and specific data for setting these priorities.     

Mass data massage: an automated data processing system used for NHEXAS, Arizona. National Human Exposure Assessment Survey.

Data entry and management are critical components of all large survey projects; data quality objectives must be met and data must be quickly and readily accessible. We developed a comprehensive system for data entry and management utilizing scannable forms with bubble fields and handwriting recognition. This 'Mass Data Massage' (MDM) system had three components: (1) form creation and database definition; (2) programming of data dictionaries for documentation and preliminary logic and range checks; and (3) data entry, management and documentation using the 'Mass Data Cleaning Program' (MDCP). Scannable forms were written in Teleform, where the data field definition, variable names and ranges were defined as the form was created. Completed forms were returned from the field, subjected to final field quality control (QC) checks, and transferred to the data management section. They were batched and coded as necessary. Once a batch of data was scanned and visually verified, the operator called up the menu for the MDCP. The MDCP had 31 program modules with 500-1200 lines of code each. The operator could select and run the appropriate dictionary on each data batch 'correcting' apparent errors in responses. This process was iterative until the data batch passed all dictionary checks. Proposed 'changes' were forwarded to the data coordinator (DC) for acceptance or rejection. After all errors had been resolved, each data batch was subjected to a 10% quality assurance (QA) check. The original data batch and associated file of applied changes were archived. Time expenditure using the scanning approach varied with the number of questions and the types of responses (handwritten or bubble fields). One-page forms took 42-60% of the time needed for hand entry; forms longer than 10 pages took 35-38% of the time. Use of faster machines will further speed the process. The main advantage of the system was the reduction of systematic errors. Scanning alone reduced errors found on 995 NHEXAS Baseline Questionnaires. Overall, the dictionary identified 0.55% errors on the scanned forms. Ten percent QC checks, performed on corrected batches ready for appendage to the master database, revealed an overall error rate of 0.02%. Similar checks on a laboratory form scanned from numeric handwriting detected 0.3% errors following dictionary application and 0.2% errors during the 10% QA check. This system was faster, more accurate, and more cost-effective than hand entry of data. A batch of data that took >1 week to process using the hand entry method was processed within 1 day using MDM. Human coding of specific answers and the final verification were the most time-consuming processes.     

Ecotoxicological evaluation of chlorpyrifos exposure on the nematode Caenorhabditis elegans

To investigate the effects of chlorpyrifos (CP), an organophosphorus insecticide, on the soil nematode Caenorhabditis elegans, the toxicity of the insecticide on the molecular, biochemical, and physiological levels were investigated upon sublethal exposure, and an acute toxicity test was conducted using lethality as an endpoint. To assess the molecular-level effect, stress-related gene expression was investigated, and the neurotoxicity indicator, acetylcholinesterase (AChE) activity was assessed as the biochemical-level response. Growth, reproduction and development were also studied as physiological-level responses. The overall results indicate that CP exposure leads to the alteration of the expression of some stress genes, such as of heat shock protein, metallothionein, vitellogenin and C. elegans p53-like protein genes; the inhibition of AChE activity; and the retardation of development. These data suggest that the toxicity of CP on C. elegans occurred in multiple biological organizations; nevertheless this is not sufficient to conclude that there is a casual relationship between them. Thus, direct experimental demonstrations of the wider relationships between the molecular/biochemical effects of CP exposure and their consequences at higher levels of biological organization are needed to fully understand the effects of this compound on C. elegans.     

Analysis of aggregate exposure to chlorpyrifos in the NHEXAS-Maryland investigation

As part of the National Human Exposure Assessment Survey (NHEXAS) in Maryland, we collected indoor air, carpet dust, exterior soil, and duplicate diet samples from a stratified random sample of 80 individuals to evaluate aggregate daily exposure, contributions of specific pathways of exposure, and temporal variation in exposure to chlorpyrifos. We collected samples from each participant in up to six equally spaced sampling cycles over a year and analyzed them for chlorpyrifos. We used chlorpyrifos concentrations in each medium and self-reported rates of time spent inside at home, time and frequency of contact with carpet, frequency of contact with soil, and weights of the duplicate diet samples to derive exposure to chlorpyrifos from each medium as well as average daily aggregate exposure (nanograms per day). The mean aggregate daily exposure to chlorpyrifos of 36 measurements obtained from 31 people was 1,390 ng/day (SD, 2,770 ng/day). Exposure from inhalation of indoor air accounted for 84.7% of aggregate daily exposure to chlorpyrifos on average. Chlorpyrifos concentrations in indoor air and carpet dust and the corresponding exposure rates were significantly correlated. Repeated short-term measurements of chlorpyrifos in carpet dust from individual residences were strongly correlated over time (reliability coefficient, R = 0.90), whereas the short-term measurements of chlorpyrifos in indoor air (R = 0.55) and solid food (R = 0.03) had moderate to weak reliability. Exposure to chlorpyrifos through those media and in aggregate based on direct measurements reported in this study can be used to understand better the accuracy of pesticide safety assessments.     

Estimating populations for collective dose calculations

The collective dose provides an estimate of the effects of facility operations on the public based on an estimate of the population in the area. Geographic information system software, electronic population data resources, and a personal computer were used to develop estimates of population within 80-km radii of two sites.     

Pesticide dose estimates for children of Iowa farmers and non-farmers

Farm children have the potential to be exposed to pesticides. Biological monitoring is often employed to assess this exposure; however, the significance of the exposure is uncertain unless doses are estimated. In the spring and summer of 2001, 118 children (66 farm, 52 non-farm) of Iowa farm and non-farm households were recruited to participate in a study investigating potential take-home pesticide exposure. Each child provided an evening and morning urine sample at two visits spaced approximately 1 month apart, with the first sample collection taken within a few days after pesticide application. Estimated doses were calculated for atrazine, metolachlor, chlorpyrifos, and glyphosate from urinary metabolite concentrations derived from the spot urine samples and compared to EPA reference doses. For all pesticides except glyphosate, the doses from farm children were higher than doses from the non-farm children. The difference was statistically significant for atrazine (p<0.0001) but only marginally significant for chlorpyrifos and metolachlor (p = 0.07 and 0.1, respectively). Among farm children, geometric mean doses were higher for children on farms where a particular pesticide was applied compared to farms where that pesticide was not applied for all pesticides except glyphosate; results were significant for atrazine (p = 0.030) and metolachlor (p = 0.042), and marginally significant for chlorpyrifos (p = 0.057). The highest estimated doses for atrazine, chlorpyrifos, metolachlor, and glyphosate were 0.085, 1.96, 3.16, and 0.34 microg/kg/day, respectively. None of the doses exceeded any of the EPA reference values for atrazine, metolachlor, and glyphosate; however, all of the doses for chlorpyrifos exceeded the EPA chronic population adjusted reference value. Doses were similar for male and female children. A trend of decreasing dose with increasing age was observed for chlorpyrifos.     

Human exposure and risk from indoor use of chlorpyrifos.

The toxicity, exposure, and risk from chlorpyrifos are briefly discussed in juxtaposition with two recent articles in Environmental Health Perspectives concerning potential exposures to children. In studies conducted according to EPA guidelines, chlorpyrifos has been shown not to be mutagenic, carcinogenic, or teratogenic, nor does it adversely affect reproduction. Chlorpyrifos toxicity does not occur in the absence of significant cholinesterase inhibition. If exposures are less than those that cause significant cholinesterase depression, then no signs or symptoms related to chlorpyrifos exposure occur. The weight of empirical evidence indicates that the risk of adults or children experiencing an adverse health effect from exposure to chlorpyrifos through both nondietary and dietary sources is negligible. Both the research supporting the registration of these products and their long history of widespread use suggest that unless these products are seriously misused, their margins of safety are wide enough to protect everyone with the potential to be exposed. A weight-of-evidence review of the entire scientific knowledge base relating to chlorpyrifos products supports these conclusions.     

煤矿及粘土矿氡暴露和矿工吸入氡子体剂量估算

对2个煤矿(A、B)、2个粘土矿(C、D)矿区的监测点进行氡含量测定。结果 4个矿区的氡浓度、氡子体浓度、氡子体所致年有效剂量当量均低于国家标准,但粘土矿浓度普遍高于煤矿。小型私有粘土矿内氡等环境问题有待改善。