Search

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.

As part of the National Human Exposure Assessment Survey (NHEXAS), residential pesticide storage and use patterns were evaluated in a population-based sample of Minnesota households with children aged 3-13. In-home interviews and inventories were conducted to identify pesticide products stored and used in and around 308 households. This statistically based sample represents more than 49,000 urban and rural households in the census tracts sampled. More than 850 unique products were identified using Environmental Protection Agency (EPA) registration numbers. Pesticide products were found in 97% and reported used in 88% of study households. Population-weighted mean values for pesticide storage and use were 6.0 and 3.1 products per household, respectively. The most common active ingredients found were diethyl toluamide (DEET) and related compounds, piperonyl butoxide, pyrethrins, dimethylamine 2-[2-methyl-4-chlorophenoxyl propionate (MCPA) and chlorpyrifos. Household socio-demographic characteristics explained little of the variability in pesticide storage and use patterns, and there were no significant differences in residential storage and use patterns between households located in urban versus non-urban census tracts. Although the prevalence of households with pesticide products was similar to recent national surveys, observed storage and use rates were almost twice those obtained in recent national studies, reflecting improved inventory techniques used by this study and/or increased rates of pesticide presence and use in study households.

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).

The National Human Exposure Assessment Survey (NHEXAS) Phase I field study conducted in EPA Region 5 provides extensive exposure data on approximately 250 study participants selected via probability sampling. Associated environmental media and biomarker (blood, urine) concentration data were also obtained to aid in the understanding of relationships of the exposures to both contaminant sources and doses. Distributional parameters for arsenic (As), lead (Pb), and four volatile organic compounds (VOCs)--benzene, chloroform, tetrachloroethylene, and trichloroethylene--were estimated for each of the relevant media using weighted data analysis techniques. Inter-media associations were investigated through correlation analysis, and longitudinal correlations and models were used to investigate longitudinal patterns. Solid food appeared to be a major contributor to urine As levels, while Pb levels in household (HH) dust, personal air, and beverages all were significantly associated with blood Pb levels. Relatively high (>0.50) longitudinal correlations were observed for tap water Pb and As, as compared to only moderate longitudinal correlations for the personal air VOCs.

For the Phase I field test of the National Human Exposure Assessment Survey (NHEXAS) in U.S. Environmental Protection Agency (EPA) Region 5, this paper presents the survey sampling design, the response rates achieved, and the sample weighting procedure implemented to compensate for unit nonresponse. To enable statistically defensible inferences to the entire region, a sample of about 250 members of the household population in EPA Region 5 was selected using a stratified multistage probability-based survey sampling design. Sample selection proceeded in four nested stages: (1) sample counties; (2) area segments based on Census blocks within sample counties; (3) housing units (HUs) within sample segments; and (4) individual participants within sample households. Each fourth-stage sample member was asked to participate in 6 days of exposure monitoring. A subsample of participants was asked to participate in two rounds of longitudinal follow-up data collection. Approximately 70% of all sample households participated in household screening interviews in which rosters of household members were developed. Over 70% of the sample subjects selected from these households completed the Baseline Questionnaire regarding their demographic characteristics and potential for exposures. And, over 75% of these sample members went on to complete at least the core environmental monitoring, including personal exposures to volatile organic compounds (VOCs) and tap water concentrations of metals. The sample weighting procedures used the data collected in the screening interviews for all household members to fit logistic models for nonresponse in the later phases of the study. Moreover, the statistical analysis weights were poststratified to 1994 State population projections obtained from the Bureau of the Census to ensure consistency with other statistics for the Region.

Exposure issues have important consequences for regulatory decisions. Reliable answers to exposure questions are critical for site cleanup, model validation, and cumulative risk issues, as well as giving perspective on our risk estimates. This paper discusses some of the important issues in designing the National Human Exposure Assessment Survey (NHEXAS) and, by implication, other exposure-monitoring-based studies as well. Sampling design issues are discussed in terms useful to exposure assessors. These issues include simple random sample designs versus more complex multistage designs, design efficiency, how to determine the sample size for the desired precision of the estimate, and the effects of stratification and oversampling on the needed sample size. This paper also discusses several important nonsampling issues such as population definition, response rates, and several potential sources of error in interpreting the monitoring results.

Particle concentrations were measured for a probability-based sample of 178 nonsmoking individuals aged 10 or older residing in Riverside, California, in the fall of 1990. Two 12-hr personal-exposure PM10 samples were obtained for each participant, along with fixed-location PM10 and PM2.5 indoor and outdoor air samples at their residences. The particle samples were also analyzed via X-ray fluorescence (XRF) to determine elemental concentrations for selected elements, including some toxic metals, crustal elements, and combustion- and industrial-source related elements. About 25% of the target population was estimated to have 24-hr personal exposures to PM10 that exceeded the national ambient air concentration standard of 150 micrograms/m3. The daytime personal exposure levels (median of 130 micrograms/m3) tended to exceed both indoor and outdoor levels by about 50%; nighttime personal exposure levels were lower and were only slightly higher than nighttime indoor levels. Several possible reasons for the elevated daytime personal PM10 levels (relative to indoor levels) are considered. Certain activities such as house cleaning and smoking were found to be associated with elevated personal exposure levels.

Seven persons volunteered to perform 25 common activities thought to increase personal exposure to volatile organic chemicals (VOCs) during a 3-day monitoring period. Personal, indoor, and outdoor air samples were collected on Tenax cartridges three times per day (evening, overnight, and daytime) and analyzed by GC-MS for 17 target VOCs. Samples of exhaled breath were also collected before and after each monitoring period. About 20 activities resulted in increasing exposure to one or more of the target VOCs, often by factors of 10, sometimes by factors of 100, compared to exposures during the sleep period. These concentrations were far above the highest observed outdoor concentrations during the length of the study. Breath levels were often significantly correlated with previous personal exposures. Major exposures were associated with use of deodorizers (p-dichlorobenzene); washing clothes and dishes (chloroform); visiting a dry cleaners (1,1,1-trichloroethane, tetrachloroethylene); smoking (benzene, styrene); cleaning a car engine (xylenes, ethylbenzene, tetrachloroethylene); painting and using paint remover (n-decane, n-undecane); and working in a scientific laboratory (many VOCs). Continuously elevated indoor air levels of p-dichlorobenzene, trichloroethylene, 1,1,1-trichloroethane, carbon tetrachloride, decane, and undecane were noted in several homes and attributed to unknown indoor sources. Measurements of exhaled breath suggested biological residence times in tissue of 12-18 hr and 20-30 hr for 1,1,1-trichloroethane and p-dichlorobenzene, respectively.

Comparison with administrative records or "best estimate file" enables an evaluation of the accuracy of household reports of mental health use in the four-State Medicaid Household Survey conducted as part of the National Medical Care Utilization and Expenditure Survey. Underreporting of probability of ambulatory mental health use ranged from 14 to 24% compared to 5 to 7% for ambulatory health visits; household estimates of number of mental health visits seemed to be more accurate than administrative records. Household reporting of provider type seemed to be very accurate for psychiatrist visits, but there seemed to be a tendency to report psychologist visits as psychiatrist visits.

Personal and telephone interview surveys were conducted simultaneously during 1981 in the same area (four counties in the area of Tampa Bay, Florida) and utilizing the same interview schedule. Following completion of the surveys, validity checks were made with the medical providers reported by a subsample of respondents to each mode. The telephone survey yielded a lower response rate but cost less than half the personal interview. There was some evidence of nonresponse bias in the telephone survey, and some relatively minor differences in responses were found between the two modes, but there was no conclusive evidence that the response differences resulted from mode effects. Telephone respondents appeared to be somewhat more accurate in their reporting of visits to medical providers, although accuracy comparisons must be interpreted with caution in view of the disparate success experienced for the two modes in securing permission forms for the release of medical record information.