Children's Pesticide Exposure Study Research Articles

Measured versus simulated dietary pesticide intakes in children

Children's dietary pesticide intakes can be measured directly through duplicate diet samples, but instead are frequently estimated using national residue data. We compared organophosphorus and pyrethroid pesticide intakes from conventional fruit, fruit juices and vegetables measured for two cohorts of children aged 3–11 years in the Children's Pesticide Exposure Study (CPES) with corresponding intakes simulated using CPES consumption and body weight data and residue data from the US Pesticide Data Program (PDP). We calculated daily measured pesticide intakes by multiplying grams eaten with measured concentrations and dividing by body weight. For the simulated intakes we combined the CPES consumption and PDP residue data, randomly sampling the PDP data 500 times in order to create distributions of daily intakes for each cohort, including 95% uncertainty intervals for each percentile. In all cases, the measured medians fell below the lower uncertainty bounds of the simulated medians, reflecting the lower detection limits of CPES versus PDP and the high number of non-detects in each. Upper percentile measured intakes were generally lower as well, except for higher measured intakes of phosalone from watermelon. This work shows that using PDP data could generate probabilistic estimates of dietary pesticide intakes that do not differ appreciably from measured intakes except in some cases.

Assessing Childrenʼs Dietary Pesticide Exposures—Pesticide Residues Measured in 24-Hour Duplicate Food Samples

ISEE-0849 Background and Objective: Characterizing dietary pesticide exposure among young children has become an essential component of cumulative risk assessment since the passage of the Food Quality Protection Act in the US, in part due to a recent reporting identifying dietary intake as a predominant source of pesticide exposure among children, particularly for organophosphorus (OP) pesticides. The objective of this study is to quantify OP and pyrethroid insecticide residues in the 24-hour duplicate food samples collected from the Children Pesticide Exposure Study (CPES). Method: We have established two CPES study groups with children ages 3–11 years, 19 and 20 children residing in Seattle, Washington (CPES-WA), and in Atlanta, Georgia (CPES-GA), respectively. The 24-hour duplicate food samples, mainly fresh vegetables, fruits, and juices, were collected from these study participants three times over a 6-month period and analyzed by US Food and Drug Administration labs in Atlanta GA and College Park MD for OP and pyrethroid insecticides. Results: The frequencies of detection for at least one pesticide in the food samples are 14.7% for CPES-WA and 22.7% for CPES-GA. For food samples that contained detectable pesticide residues, we found 42% and 24% of those contain multiple residues in CPES-WA and CPES-GA, respectively. We found most of the OP residues in the fruit category, whereas pyrthroids were commonly detected in vegetables. The highest residues that we found in all the food samples were 350 ppb of Acephate (OP) in celery and 921 ppb of Permethrin (pyrethroids) in a composite food sample of strawberries and spinach. Conclusion: We found 19 out of 100 food samples that children commonly consumed that contained at least one insecticide that is known as neurotoxin. These data will be valuable for validating urinary exposure biomarkers for the respective insecticides, as well as dietary risk assessment.

Comparison of food consumption frequencies among NHANES and CPES children: Implications for dietary pesticide exposure and risk assessment

Characterizing food consumption patterns among children is critical to dietary pesticide exposure assessment. We have used public release data from the US National Health and Nutrition Examination Survey (NHANES) and the longitudinal Children's Pesticide Exposure Study (CPES) to illustrate the magnitude of potential error introduced by using national-scale, cross-sectional data to estimate the consumption frequencies for smaller cohorts. We focused on foods commonly consumed by children in the target CPES age and income group (3-11 years; annual household income >$75,000) and foods likely to contain organophosphorus or pyrethroid pesticide residues. We defined "percent eaters" as the percentage of study participants who reported eating a particular food in a 24-h period. We computed the weighted percent eaters and 95% confidence limits (CL) for the target age/income group using the NHANES 24-h dietary recall data and compared these with the CPES percent eaters by sampling day and season. For certain foods, particularly the seasonally available produce (for example, apples, peaches/nectarines, melon, grapes, pears, strawberries), soy milk, and peanut butter, the CPES percent eaters fell outside the NHANES 95% CLs on many sampling days. For other foods (for example, orange juice and cow's milk), differences were not readily apparent. Although the differences we observed for certain foods may be, in part, because of measurement error, they also likely reflect seasonal and geographic patterns among the CPES data that the public release NHANES data do not capture. Using NHANES data to estimate pesticide intakes from strawberries, for example, may underestimate the exposure of the CPES children, as significantly more CPES than NHANES children ate strawberries on many sampling days. For other sampling days or other foods, overestimation is also possible.

Multiresidue Analysis of 102 Organophosphorus Pesticides in Produce at Parts-per-Billion Levels Using a Modified QuEChERS Method and Gas Chromatography with Pulsed Flame Photometric Detection

A multiresidue method for the analysis of organophosphorus pesticides in fresh produce at levels down to 1.0 microg/kg (ppb) has been developed using a modification of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. The procedure entails extraction of pesticides from the sample with acetonitrile, salting-out with magnesium sulfate (MgSO4) and sodium chloride, and cleanup of the resulting extracts with dispersive solid-phase extraction using primary-secondary amine, graphitized carbon black, and MgSO4. Fortification studies were performed for 102 organophosphorus pesticides at 1.0, 10, and 100 ppb in 4 different pesticide-free commodities (grape, orange, spinach, and tomato). Recoveries ranged from 63-125%, with >80% being achieved for most of the pesticides tested in each commodity. The procedure was applied to the analysis of 400 produce samples collected from a cohort of children that participated in the Children's Pesticide Exposure Study and the Longitudinal Dietary Pesticide Exposure Study in which selected 24 h duplicate food items were collected throughout a 12-month period. Residues of 15 of the 102 pesticides were detected at levels ranging from <1 to 526 ppb.

A novel system for collecting longitudinal self-reported dietary consumption information: The internet data logger (iDL)

As diet has been considered as the major exposure pathway for toxic chemicals, such as heavy metals and pesticides, we have developed a web-based questionnaire system, the internet data logger (iDL), in order to facilitate the collection of detailed self-recording of standardized daily dietary consumption. An iDL prototype optimized for hand-held devices was tested in the on-going Children's Pesticide Exposure Study (CPES) in Atlanta, GA in which 15 consecutive days of dietary consumption information were recorded by 11 children or their parents and transmitted to a server via broadband wireless internet connection. Participants spent an average of 6.2 min in day 1 to enter a meal into iDL and approximately 4 min per meal for the remaining 14 study days. Approximately 75% of 446 total meals were entered into iDL on the date of consumption. A within-person comparison revealed that many food items recorded on paper diary were later classified as "unknown" according to iDL standards due to the lack of detailed information provided by the participants. The development of iDL represents a novel and pioneering tool, which integrates dietary data collection, transmission, and management in a real-time and automated manner. iDL provides the needed flexibility and mobility for research focused on collecting not only dietary consumption data but also other time-sensitive behavior data. This study has demonstrated that iDL can be deployed to collect long-term dietary consumption information in a population-based study, though future modifications/enhancements will undoubtedly improve its usability and application.

Comparison of recruitment, retention, and compliance results for three children's exposure monitoring studies

The School Health Initiative: Environment, Learning, Disease (SHIELD) study, the Minnesota Children's Pesticide Exposure Study (MNCPES), and the National Cooperative Inner-City Asthma Study (NCICAS) are three of the most intensive and invasive exposure-monitoring projects ever undertaken in children. An intrinsic facet of each study was the need to recruit children and their families, retain them for the duration of the project, and ensure that they completed monitoring protocols successfully. All of the studies used fiscal incentives to encourage participation, retention, and compliance. Recruitment rates varied from 40% in MNCPES, to 57% in SHIELD, to 64% in NCICAS, while retention rates varied from 85% in SHIELD, to 94% in MNCPES, to 95% in NCICAS. Rates of compliance with exposure sampling procedures were typically >80% for each study. For example, > or =85% of the enrolled children provided all requested urine samples (1 for NCICAS, 2 for SHIELD, 3 for MNCPES), and 82% of the children in SHIELD provided two out of two blood samples (optional in MNCPES and NCICAS). However, compliance rates were substantially lower (34% SHIELD, 40% NCICAS, not applicable to MNCPES) for the more complex and time-consuming protocol used to collect peak flow data. Overall, results demonstrate that it is practical and affordable to conduct demanding exposure-monitoring studies in children, including children from poor minority communities.

Constraining uncertainties about the sources and magnitude of polycyclic aromatic hydrocarbon (PAH) levels in ambient air: the state of Minnesota as a case study

Emissions data are often lacking or uncertain for many airborne contaminants. Polycyclic aromatic hydrocarbons (PAHs) emitted from combustion sources fall into this category. Currently available ambient-air emission inventories of PAHs either fail to account for population-based activities, such as residential wood combustion (RWC) and motor vehicle (MV) activity, and/or report “total PAH” or particulate organic matter emissions, instead of individual compound emissions. We assess the degree of overlap between predicted concentrations from estimated emissions with measured concentrations. Our analysis is based on probabilistic analysis of measured outdoor air concentrations with those predicted from mass-balance models. Based on available information, we estimate the relative magnitude of emissions from three major sources of PAHs to outdoor air: (1) on-road MVs, including light-duty gasoline vehicles and diesel-powered buses and medium and heavy-duty trucks; (2) RWC; and (3) power generation from external combustion boilers. We use the CalTOX regional multimedia mass-balance model to evaluate our emissions estimates in rural and urban regions of the state of Minnesota, USA. We compare model estimates of outdoor PAH airborne concentrations with those reported by the Minnesota Children's Pesticide Exposure Study (MNCPES). With these measured concentrations we probabilistically evaluate the reliability of our emissions estimates for specific PAHs. The median estimates of our predicted outdoor air concentrations agree within an order of magnitude of measured concentrations. For four representative PAHs, we obtain a reasonable degree of overlap between empirical and predicted distributions of outdoor air concentrations. Our combination of models, emissions estimates, and empirical concentration data estimate exposure in a manner that is more reliable than any of these tools alone. Thereby, we increase our confidence about our plausible ranges of emissions and predicted concentrations.

Personal, indoor, and outdoor VOC exposures in a probability sample of children.

As part of the Minnesota Children's Pesticide Exposure Study we measured volatile organic compound (VOC) concentrations in a probability sample of households with children. The 6-day average concentrations for 10 common VOCs were obtained in urban and nonurban residences twice during this multiphase study: screening-phase indoor measurements were collected in 284 households, and in the intensive-phase matched outdoor (O), indoor (I), and personal (P) measurements were collected in a subset (N=72) of the screened households. Screening-phase households with smokers had significantly higher concentrations of benzene and styrene compared to nonsmoking households; households with an attached garage had significantly higher levels of benzene, chloroform, styrene, and m/p- and o-xylene compared to households without an attached garage; and nonurban residences, which had a greater prevalence of smokers and attached garages, had significantly higher 1,1,1-trichloroethane, styrene, and toluene and significantly lower tetrachloroethylene concentrations compared to urban households. The screening-phase weighted distributions estimate the mean and variability in indoor VOC concentrations for more than 45,000 households with children in the census tracts sampled. Overall, median indoor concentrations of most VOCs measured in this study were similar to or lower than indoor levels measured previously in the United States. Intensive-phase outdoor VOC concentrations were generally lower than other major metropolitan areas, but urban concentrations were significantly higher than nonurban concentrations for all compounds except 1,1,1-trichloroethylene. A consistent pattern of P>I>O was observed for nine of 10 VOCs, with 1,1,1-trichloroethylene (I>P>O) being the only exception to this pattern. For most children, the indoor at-home microevironment was strongly associated with personal exposure after controlling for important covariates, but the ratio of median to upper bound exposures was smaller than that observed in studies of adults. There are relatively little data on VOC exposures in children, so these results are useful for estimating the central tendency and distribution of VOC exposures in locations where children spend a majority of their time.

Erratum: Assessment of the data quality for the NHEXAS—Part II: Minnesota children's pesticide exposure study (MNCPES)

Journal of Exposure Analysis and Environmental Epidemiology (2003) 13, 465–479. doi: 10.1038/sj.jea.7500315

Distributions, associations, and partial aggregate exposure of pesticides and polynuclear aromatic hydrocarbons in the Minnesota Children's Pesticide Exposure Study (MNCPES).

The Minnesota Children's Pesticide Exposure Study (MNCPES) provides exposure, environmental, and biologic data relating to multipathway exposures of children for four primary pesticides (chlorpyrifos, malathion, diazinon, and atrazine), 14 secondary pesticides, and 13 polynuclear aromatic hydrocarbons (PAHs). Monitoring was performed on a probability-based sample of 102 children aged 3-12 in Minneapolis/St. Paul and in a nearby rural area (Goodhue and Rice counties). This paper provides estimated distributions of this population's exposures and exposure-related measurements and examines associations among the various measures via rank (Spearman) correlations. In addition, it provides some aggregate and cumulative exposure estimates for pesticides, and compares the relative intakes from inhalation and dietary ingestion. Intakes for the four primary pesticides appeared to come principally from the ingestion rather than the inhalation route; this was clearly true for chlorpyrifos but was less certain for the other three primary pesticides because of their higher degree of nondetects. Solid food rather than beverages was clearly the main contributor to the ingestion intake. Despite the dominance of the ingestion route, the urinary metabolite of chlorpyrifos exhibited a stronger association with the air measurements than with the dietary measures. Personal-air samples exhibited strong rank correlations with indoor air samples for chlorpyrifos, malathion, and diazinon (0.81, 0.51, and 0.62, respectively), while personal-air atrazine levels correlated well with outdoor levels (0.69); personal-air diazinon levels also correlated well with outdoor levels (0.67). For the PAHs, many significant associations were evident among the various air samples and for the air samples with the dust samples, especially for those compounds with consistently high percent measurable values (particularly fluoranthene, phenanthrene, and pyrene).

Predicting children's short-term exposure to pesticides: results of a questionnaire screening approach.

The ability of questionnaires to predict children's exposure to pesticides was examined as part of the Minnesota Children's Pesticide Exposure Study (MNCPES). The MNCPES focused on a probability sample of 102 children between the ages of 3 and 13 years living in either urban (Minneapolis and St. Paul, MN) or nonurban (Rice and Goodhue Counties in Minnesota) households. Samples were collected in a variety of relevant media (air, food, beverages, tap water, house dust, soil, urine), and chemical analyses emphasized three organophosphate insecticides (chlorpyrifos, diazinon, malathion) and a herbicide (atrazine). Results indicate that the residential pesticide-use questions and overall screening approach used in the MNCPES were ineffective for identifying and oversampling children/households with higher levels of individual target pesticides.

Quantitative analysis of children's microactivity patterns: The Minnesota Children's Pesticide Exposure Study.

The National Human Exposure Assessment Survey (NHEXAS)/Minnesota Children's Pesticide Exposure Study (MNCPES) was a population-based study designed to characterize children's exposure to residential pesticides and to evaluate the contribution of residential and children's activities to children's exposure. Families of 168 children were surveyed for residential use of pesticides and children's activities. From these homes, families of 102 children between the ages of 3 and 13 years participated in a week-long intensive exposure study. Of the 102 children, 19 children were videotaped for four consecutive hours in their normal daily activities. The survey responses indicated that the youngest children were more likely to exhibit behaviors that would foster exposure to environmental contaminants. Comparison of questionnaire responses indicated that the videotaped subsample was representative of the exposure study population. The microactivities of the videotaped children that might contribute to their exposure via ingestion or dermal routes were quantified. Hand-to-mouth and object-to-mouth activities were observed most frequently among the youngest children. The youngest children were also most likely to be barefoot both indoors and outside. Gender differences were found in mouthing behavior and the proportion of observed time spent outdoors.

Measurement of children's exposure to pesticides: analysis of urinary metabolite levels in a probability-based sample.

The Minnesota Children's Pesticide Exposure Study is a probability-based sample of 102 children 3-13 years old who were monitored for commonly used pesticides. During the summer of 1997, first-morning-void urine samples (1-3 per child) were obtained for 88% of study children and analyzed for metabolites of insecticides and herbicides: carbamates and related compounds (1-NAP), atrazine (AM), malathion (MDA), and chlorpyrifos and related compounds (TCPy). TCPy was present in 93% of the samples, whereas 1-NAP, MDA, and AM were detected in 45%, 37%, and 2% of samples, respectively. Measured intrachild means ranged from 1.4 microg/L for MDA to 9.2 microg/L for TCPy, and there was considerable intrachild variability. For children providing three urine samples, geometric mean TCPy levels were greater than the detection limit in 98% of the samples, and nearly half the children had geometric mean 1-NAP and MDA levels greater than the detection limit. Interchild variability was significantly greater than intrachild variability for 1-NAP (p = 0.0037) and TCPy (p < 0.0001). The four metabolites measured were not correlated within urine samples, and children's metabolite levels did not vary systematically by sex, age, race, household income, or putative household pesticide use. On a log scale, mean TCPy levels were significantly higher in urban than in nonurban children (7.2 vs. 4.7 microg/L; p = 0.036). Weighted population mean concentrations were 3.9 [standard error (SE) = 0.7; 95% confidence interval (CI), 2.5, 5.3] microg/L for 1-NAP, 1.7 (SE = 0.3; 95% CI, 1.1, 2.3) microg/L for MDA, and 9.6 (SE = 0.9; 95% CI, 7.8, 11) microg/L for TCPy. The weighted population results estimate the overall mean and variability of metabolite levels for more than 84,000 children in the census tracts sampled. Levels of 1-NAP were lower than reported adult reference range concentrations, whereas TCPy concentrations were substantially higher. Concentrations of MDA were detected more frequently and found at higher levels in children than in a recent nonprobability-based sample of adults. Overall, Minnesota children's TCPy and MDA levels were higher than in recent population-based studies of adults in the United States, but the relative magnitude of intraindividual variability was similar for adults and children.

Measurement of Children's Exposure to Pesticides: Analysis of Urinary Metabolite Levels in a Probability-Based Sample

The Minnesota Children's Pesticide Exposure Study is a probability-based sample of 102 children 3-13 years old who were monitored for commonly used pesticides. During the summer of 1997, first-morning-void urine samples (1-3 per child) were obtained for 88% of study children and analyzed for metabolites of insecticides and herbicides: carbamates and related compounds (1-NAP), atrazine (AM), malathion (MDA), and chlorpyrifos and related compounds (TCPy). TCPy was present in 93% of the samples, whereas 1-NAP, MDA, and AM were detected in 45%, 37%, and 2% of samples, respectively. Measured intrachild means ranged from 1.4 microg/L for MDA to 9.2 microg/L for TCPy, and there was considerable intrachild variability. For children providing three urine samples, geometric mean TCPy levels were greater than the detection limit in 98% of the samples, and nearly half the children had geometric mean 1-NAP and MDA levels greater than the detection limit. Interchild variability was significantly greater than intrachild variability for 1-NAP (p = 0.0037) and TCPy (p &lt; 0.0001). The four metabolites measured were not correlated within urine samples, and children's metabolite levels did not vary systematically by sex, age, race, household income, or putative household pesticide use. On a log scale, mean TCPy levels were significantly higher in urban than in nonurban children (7.2 vs. 4.7 microg/L; p = 0.036). Weighted population mean concentrations were 3.9 [standard error (SE) = 0.7; 95% confidence interval (CI), 2.5, 5.3] microg/L for 1-NAP, 1.7 (SE = 0.3; 95% CI, 1.1, 2.3) microg/L for MDA, and 9.6 (SE = 0.9; 95% CI, 7.8, 11) microg/L for TCPy. The weighted population results estimate the overall mean and variability of metabolite levels for more than 84,000 children in the census tracts sampled. Levels of 1-NAP were lower than reported adult reference range concentrations, whereas TCPy concentrations were substantially higher. Concentrations of MDA were detected more frequently and found at higher levels in children than in a recent nonprobability-based sample of adults. Overall, Minnesota children's TCPy and MDA levels were higher than in recent population-based studies of adults in the United States, but the relative magnitude of intraindividual variability was similar for adults and children.

Measurement of multi-pollutant and multi-pathway exposures in a probability-based sample of children: practical strategies for effective field studies.

The purpose of this manuscript is to describe the practical strategies developed for the implementation of the Minnesota Children's Pesticide Exposure Study (MNCPES), which is one of the first probability-based samples of multi-pathway and multi-pesticide exposures in children. The primary objective of MNCPES was to characterize children's exposure to selected pesticides through a combination of questionnaires, personal exposure measurements (i.e., air, duplicate diet, hand rinse), and complementary monitoring of biological samples (i.e., pesticide metabolites in urine), environmental samples (i.e., residential indoor/outdoor air, drinking water, dust on residential surfaces, soil), and children's activity patterns. A cross-sectional design employing a stratified random sample was used to identify homes with age-eligible children and screen residences to facilitate oversampling of households with higher potential exposures. Numerous techniques were employed in the study, including in-person contact by locally based interviewers, brief and highly focused home visits, graduated subject incentives, and training of parents and children to assist in sample collection. It is not feasible to quantify increases in rates of subject recruitment, retention, or compliance that resulted from the techniques employed in this study. Nevertheless, results indicate that the total package of implemented procedures was instrumental in obtaining a high percentage of valid samples for targeted households and environmental media.

House dust levels of selected insecticides and a herbicide measured by the EL and LWW samplers and comparisons to hand rinses and urine metabolites.

During the Minnesota Children's Pesticide Exposure Study (MNCPES), comparisons were made between the insecticide/herbicide loadings obtained with two household dust/insecticide or herbicide samplers: the Edwards and Lioy (EL) press sampler (used for dust collection from carpets or other surfaces) and the Lioy, Waimnan and Weisel (LWW) surface wipe sampler. The results were compared with hand rinse levels, and urine metabolite levels obtained from 102 children (ages 3-13). All measurements were made during a 1-week sampling period, and information was obtained on household pesticide use and each child's activities. Of the homes, <5% had recent spot uses of a pesticide but none had recent general applications. The analyses focused primarily on atrazine (a herbicide), and malathion, diazinon, and chlorpyrifos (insecticides). Metabolites were measured for atrazine, malathion and chlorpyrifos. The atrazine levels obtained using the EL indicate that this compound was transported into the home by an unquantified transport mechanism (e.g. tracking of soil). Two malathion hand rinse values exceeded >170 ng/cm2, suggesting that since indoor surface levels were low, these children had other sources of exposure. Atrazine, chlorpyrifos and malathion were detectable in >30% of the homes by the EL, LWW or hand rinse. Only chlorpyrifos had detectable levels in > or = 50% of the samples for all types, i.e. compound or metabolite, which is consistent with it being a common household pesticide. The median (and maximum) chlorpyrifos levels for the EL surface, EL carpet, LWW surface (two rooms), hand rinse, and urine metabolites were: 0.07 (32.6) ng/cm2; 0.07 (44.5) ng/cm2; 0.34 (3.64) ng/cm2; 0.42 (14.4) ng/cm2; 0.03 (2.14) ng/hand and 6.9 (59.0) microg/g, respectively. A strong correlation was found for chlorpyrifos between the EL surface and carpet samples. Chlorpyrifos levels detected by LWW had a different distribution and concentration range than the EL, indicating that it collected more than the surface dislodgeable insecticide. EL was directly comparable to the hand rinse or urine levels, but only the LWW had a weak correlation with hand rinse levels, suggesting that the children had other sources of chlorpyrifos exposure. Thus, mechanistic exposure studies are needed to more accurately establish exposure dose relationships in residential settings.

Design strategy for assessing multi-pathway exposure for children: the Minnesota Children's Pesticide Exposure Study (MNCPES).

Although children are exposed to a variety of environmental hazards, including pesticides, there is a scarcity of information available to estimate exposures realistically. This article reports on one of the first attempts to measure multi-pathway pesticide exposures in a population-based sample of urban and non-urban children. A design strategy was developed to assess multi-pathway pesticide exposures in children using personal exposure measurements in combination with complimentary measurements of biological markers of exposure, concentrations in relevant environmental media, and time spent in important microenvironments and participating in exposure-related activities. Sample collection and analysis emphasized measurement of three insecticides (i.e., chlorpyrifos, diazinon, and malathion) and one herbicide (i.e., atrazine). These compounds were selected because of their frequent use, presence in multiple environmental media, expected population exposures, and related hazard/toxicity. The study was conducted during the summer of 1997 in Minnesota and involved a stratified sample of households with children ages 3-12 years. Participants resided in either (a) the cities of Minneapolis and St. Paul (urban households), or (b) Rice and Goodhue Counties just south of the metropolitan area (non-urban households). Results from a residential inventory documenting storage and use of products containing the target pesticides were used to preferentially select households where children were likely to have higher exposures. The study successfully obtained pesticide exposure data for 102 children, including measurements of personal exposures (air, hand rinse, duplicate diet), environmental concentrations (residential indoor/outdoor air, drinking water, residential surfaces, soil), activity patterns (obtained by questionnaire, diary, videotaping), and internal dose (metabolites in urine).