A field comparison of volatile organic compound measurements using passive organic vapor monitors and stainless steel canisters

Concurrent field measurements of 10 volatile organic compounds (VOCs) were made using passive diffusion-based organic vapor monitors (OVMs) and the U.S. Federal Reference Method, which comprises active monitoring with stainless steel canisters (CANs). Measurements were obtained throughout a range of weather conditions, repeatedly over the course of three seasons, and at three different locations in the Minneapolis/St. Paul metropolitan area. Ambient concentrations of most VOCs as measured by both methods were low compared to those of other large metropolitan areas. For some VOCs a considerable fraction of measurements was below the detection limit of one or both methods. The observed differences between the two methods were similar across measurement sites, seasons, and meteorological variables. A Bayesian analysis with uniform priors on the differences was applied, with accommodation of sometimes heavy censoring (nondetection) in either device. The resulting estimates of bias and standard deviation of the OVM relative to the CAN were computed by tertile of the canister-measured concentration. In general, OVM and CAN measurements were in the best agreement for benzene and other aromatic compounds with hydrocarbon additions (ethylbenzene, toluene, and xylenes). The two methods were not in such good agreement for styrene and halogenated compounds (carbon tetrachloride, p-dichlorobenzene, methylene chloride, and trichloroethylene). OVMs slightly overestimated benzene concentrations and carbon tetrachloride at low concentrations, but in all other cases where significant differences were found, OVMs underestimated relative to canisters. Our study indicates that the two methods are in agreement for some compounds, but not all. We provide data and interpretation on the relative performance of the two VOC measurement methods, which facilitates intercomparisons among studies.

Children's exposure to volatile organic compounds as determined by longitudinal measurements in blood

Blood concentrations of 11 volatile organic compounds (VOCs) were measured up to four times over 2 years in a probability sample of more than 150 children from two poor, minority neighborhoods in Minneapolis, Minnesota. Blood levels of benzene, carbon tetrachloride, trichloroethene, and m-/p-xylene were comparable with those measured in selected adults from the Third National Health and Nutrition Examination Survey (NHANES III), whereas concentrations of ethylbenzene, tetrachloroethylene, toluene, 1,1,1-trichloroethane, and o-xylene were two or more times lower in the children. Blood levels of styrene were more than twice as high, and for about 10% of the children 1,4-dichlorobenzene levels were greater than or equal to 10 times higher compared with NHANES III subjects. We observed strong statistical associations between numerous pairwise combinations of individual VOCs in blood (e.g., benzene and m-/p-xylene, m-/p-xylene and o-xylene, 1,1,1-trichloroethane and m-/p-xylene, and 1,1,1-trichloroethane and trichloroethene). Between-child variability was higher than within-child variability for 1,4-dichlorobenzene and tetrachloroethylene. Between- and within-child variability were approximately the same for ethylbenzene and 1,1,1-trichloroethane, and between-child was lower than within-child variability for the other seven compounds. Two-day, integrated personal air measurements explained almost 79% of the variance in blood levels for 1,4-dichlorobenzene and approximately 20% for tetrachloroethylene, toluene, m-/p-xylene, and o-xylene. Personal air measurements explained much less of the variance (between 0.5 and 8%) for trichloroethene, styrene, benzene, and ethylbenzene. We observed no significant statistical associations between total urinary cotinine (a biomarker for exposure to environmental tobacco smoke) and blood VOC concentrations. For siblings living in the same household, we found strong statistical associations between measured blood VOC concentrations.

Outdoor, indoor, and personal exposure to VOCs in children

We measured volatile organic compound (VOC) exposures in multiple locations for a diverse population of children who attended two inner-city schools in Minneapolis, Minnesota. Fifteen common VOCs were measured at four locations: outdoors (O), indoors at school (S), indoors at home (H), and in personal samples (P). Concentrations of most VOCs followed the general pattern O approximately equal to S < P less than or equal to H across the measured microenvironments. The S and O environments had the smallest and H the largest influence on personal exposure to most compounds. A time-weighted model of P exposure using all measured microenvironments and time-activity data provided little additional explanatory power beyond that provided by using the H measurement alone. Although H and P concentrations of most VOCs measured in this study were similar to or lower than levels measured in recent personal monitoring studies of adults and children in the United States, p-dichlorobenzene was the notable exception to this pattern, with upper-bound exposures more than 100 times greater than those found in other studies of children. Median and upper-bound H and P exposures were well above health benchmarks for several compounds, so outdoor measurements likely underestimate long-term health risks from children's exposure to these compounds.

Evaluating differences between measured personal exposures to volatile organic compounds and concentrations in outdoor and indoor air

Accurate estimation of human exposures to volatile organic compounds (VOCs) is a key element of strategies designed to protect public health from the adverse effects of hazardous air pollutants. The focus here is on examining the capability of three different exposure metrics (outdoor community concentrations, indoor residential concentrations, and a simple time-weighted model) to estimate observed personal exposures to 14 VOCs. The analysis is based on 2-day average concentrations of individual VOCs measured concurrently in outdoor (O) air in three urban neighborhoods, indoor (I) air in participant's residences, and personal (P) air near the breathing zone of 71 healthy, nonsmoking adults. A median of four matched P-I-O samples was collected for each study participant in Minneapolis/St. Paul over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). Results show a clear pattern for the 14 VOCs, with P > I > O concentrations. Intra-individual variability typically spanned at least an order of magnitude, and inter-individual variability spanned 2 or more orders of magnitude for each of the 14 VOCs. Although both O and I concentrations generally underestimated personal exposures, I concentrations provided a substantially better estimate of measured P concentrations. Mean squared error (MSE) as well as correlation measures were used to assess estimator performance at the subject-specific level, and hierarchical, mixed effects models were used to estimate the bias and variance components of MSE by tertile of personal exposure. Bias and variance both tended to increase in the upper third of the P exposure distribution for O versus P and I versus P. A simple time-weighted model incorporating measured concentrations in both outdoor community air and indoor residential air provided no improvement over I concentration alone for the estimation of P exposure.

Comparing air dispersion model predictions with measured concentrations of VOCs in urban communities

Air concentrations of nine volatile organic compounds were measured over 48-h periods at 23 locations in three communities in the Minneapolis-St. Paul metropolitan area. Concentrations at the same times and locations were modeled using a standard regulatory air dispersion model (ISCST3). The goal of the study was to evaluate model performance by comparing predictions with measurements using linear regression and estimates of bias. The modeling, done with mobile and area source emissions resolved to the census tract level and characterized as model area sources, represents an improvement over large-scale airtoxics modeling analyses done to date. Despite the resolved spatial scale, the model did not fully capture the spatial resolution in concentrations in an area with a sharp gradient in emissions. In a census tract with a major highway at one end of the tract (i.e., uneven distribution of emissions within the tract), model predictions atthe opposite end of the tract overestimated measured concentrations. This shortcoming was seen for pollutants emitted mainly by mobile sources (benzene, ethylbenzene, toluene, and xylenes). We suggest that major highways would be better characterized as line sources. The model also failed to fully capture the temporal variability in concentrations, which was expected since the emissions inventory comprised annual average values. Based on our evaluation metrics, model performance was best for pollutants emitted mainly from mobile sources and poorest for pollutants emitted mainlyfrom area sources. Important sources of error appeared to be the source characterization (especially location) and emissions quantification. We expect that enhancements in the emissions inventory would give the greatest improvement in results. As anticipated for a Gaussian plume model, performance was dramatically better when compared to measurements that were not matched in space or time. Despite the limitations of our analysis, we found thatthe regulatory air dispersion model was generally able to predict space and time matched 48-h average ambient concentrations of VOC species within a factor of 2 on average, results that meet regulatory model acceptance criteria.

Children's exposure to environmental tobacco smoke: using diverse exposure metrics to document ethnic/racial differences

Four metrics were used to assess exposure to environmental tobacco smoke (ETS) for a probability sample (n = 152) of elementary school-age children in two economically disadvantaged neighborhoods: a) caregiver responses to a baseline questionnaire (BQ) about smoking status and behavior; b) 48-hr time-activity (T-A) data on location and time spent by children in the presence of tobacco smoke; c) total urinary cotinine as a marker for nicotine uptake; and d) urinary NNAL [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol] + NNAL-Gluc [4-(methylnitrosamino)-1- (3-pyridyl)-1-(O-beta-D-glucopyranuronosyl)butane] as a marker for uptake of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Consistent differences in ETS exposure by ethnicity and race were observed. Although data were insufficient to determine differences for NNAL + NNAL-Gluc, BQ responses, T-A data, and cotinine levels all indicated that average ETS exposure was highest for African-American children, moderately high for those designated "other" (white, Southeast Asian, Native American), moderately low for Hispanic children, and lowest for Somali immigrant children. For example, in February 2000, mean cotinine levels were 14.1 ng/mL for African Americans, 12.2 ng/mL for other, 4.8 ng/mL for Hispanics, and 4.4 ng/mL for Somalis. The BQ and T-A data together were reasonably good predictors of total cotinine levels (adjusted r2 = 0.69), and based on limited data, measured total cotinine values were a relatively good predictor of NNAL + NNAL-Gluc (adjusted r2 = 0.73). The results suggest that when children are exposed to ETS primarily in their homes, questionnaires and T-A logs might be effective screening tools for identifying those likely to experience higher uptake of nicotine.

Comparison of personal, indoor, and outdoor exposures to hazardous air pollutants in three urban communities

Two-day average concentrations of 15 individual volatile organic compounds (VOCs) were measured concurrently in (a) ambient air in three urban neighborhoods, (b) air inside residences of participants, and (c) personal air near the breathing zone of 71 healthy, nonsmoking adults. The outdoor (O), indoor (I), and personal (P) samples were collected in the Minneapolis/St. Paul metropolitan area over three seasons (spring, summer, and fall) in 1999 using charcoal-based passive air samplers (3M model 3500 organic vapor monitors). A hierarchical, mixed-effects statistical model was used to estimate the mutually adjusted effects of monitor location, community, and season while accounting for within-subject and within-time-index (monitoring period) correlation. Outdoor VOC concentrations were relatively low compared to many other urban areas, and only minor seasonal differences were observed. A consistent pattern of P > I > O was observed across both communities and seasons for 13 of 15 individual VOCs (exceptions were carbon tetrachloride and chloroform). Results indicate that ambient VOC measurements at central monitoring sites can seriously underestimate actual exposures for urban residents, even when the outdoor measurements are taken in their own neighborhoods.

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.

Recruitment, retention, and compliance results from a probability study of children's environmental health in economically disadvantaged neighborhoods

The School Health Initiative: Environment, Learning, and Disease (SHIELD) study used a probability sample of children (second through fifth grades) from two low-income and racially mixed neighborhoods of Minneapolis, Minnesota, to assess childhood environmental health. Children were eligible to participate in SHIELD regardless of whether they or their families spoke a foreign language, their household had a telephone, or they were enrolled in a special education program. The overall enrollment rate in year 1 was 57%, with a substantial disparity between children from English-speaking (42%) versus non-English-speaking (71%) families. At the end of year 1, 85% were retained in the study. A relatively high percentage of children provided the two requested blood (82%) and urine (86%) samples in year 1, and 90% provided a valid spirometry sample. Eighty-two percent provided both requested volatile organic chemical badge samples, and both time-activity logs were obtained from 66%. However, only 32% provided both peak flow measurements. All percentages increased for those participating in the second year of the study. Results indicate that a school-based research design makes it feasible and practical to conduct probability-based assessments of children's environmental health in economically disadvantaged and ethnically diverse neighborhoods. There is an ongoing need, however, to improve understanding of the cultural, economic, psychologic, and social determinants of study participation among this population.

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.

Promoting pollution prevention through community-industry dialogues: the good neighbor model in Minnesota

This article examines five attempts by communities to promote pollution prevention through direct negotiations with local manufacturing plants. These projects were Good Neighbor Dialogues spearheaded by Citizens for a Better Environment-Minnesota, an environmental advocacy organization. Three community-company partnerships (a container plant, a foundry, and a cabinet manufacturer) were successful and two (a munitions plant and a petroleum refinery) were not. Successful dialogues all shared certain characteristics: the company was open to negotiating with the community; there was an effective "champion" within the company; a skilled, independent facilitator served as moderator; community participants received independent technical assistance; and both the company and community understood the value of cooperative environmental decision making. Results suggest that Good Neighbor Dialogues can, under the right settings and circumstances, be an effective mechanism for building social capital by fostering greater understanding and trust between companies and communities. They offer the prospect of community-company partnerships that promote pollution prevention and other environmental improvements, while at the same time reinforcing and amplifying traditional pollution control strategies.

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.

Metabolites of a tobacco-specific lung carcinogen in the urine of elementary school-aged children

Limited data are available in the literature on carcinogen uptake by children exposed to environmental tobacco smoke (ETS). In this study, we quantified metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the urine of elementary school-aged children participating in the School Health Initiative: Environment, Learning, Disease study, a school-based investigation of the environmental health of children. The metabolites of NNK are 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronide (NNAL-Gluc). We also measured cotinine and its glucuronide (total cotinine). Urine samples were collected from 204 children. Seventy (34.3%) of these had total cotinine > or =5 ng/ml. NNAL or NNAL-Gluc was detected in 52 of 54 samples with total cotinine > or =5 ng/ml and in 10 of 20 samples with total cotinine < 5 ng/ml. Levels of NNAL plus NNAL-Gluc and total cotinine were significantly higher when exposure to ETS was reported than when no exposure was reported. However, even when no exposure to ETS was reported, levels of NNAL, NNAL-Gluc, and NNAL plus NNAL-Gluc were higher than in children with documented low exposure to ETS, as determined by cotinine levels < 5 ng/ml. Levels of NNAL, NNAL-Gluc, and cotinine were not significantly different in samples collected twice from the same children at 3-month intervals. Levels of NNAL plus NNAL-Gluc in this study were comparable with those observed in our previous field studies of adults exposed to ETS. There was a 93-fold range of NNAL plus NNAL-Gluc values in the exposed children. The results of this study demonstrate widespread and considerable uptake of the tobacco-specific lung carcinogen NNK in this group of elementary school-aged children, raising important questions about potential health risks. Our data indicate that objective biomarkers of carcinogen uptake are important in studies of childhood exposure to ETS and cancer later in life.

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 < 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.

Residential proximity to industrial sources of air pollution: interrelationships among race, poverty, and age

This study builds on earlier work investigating statistical relationships between sociodemographic characteristics of populations and their residential proximity to industrial sources of air pollution. The analysis uses demographic data from the 1990 U.S. Census and industrial site data from the U.S. Environmental Protection Agency (EPA)'s 1990 Toxics Release Inventory (TRI). The focus is on examining interactions among race (African Americans and Whites), poverty (above and below household poverty threshold), and age (children from birth to 5 years of age and elderly people 65 years old or older). Results from three different study areas (Kanawha Valley in West Virginia, the Baton Rouge-New Orleans Corridor in Louisiana, and the greater Baltimore metropolitan area in Maryland) suggest there are important interactions among race, poverty, and age that are likely to have consequential ramifications for efforts aimed at investigating issues related to environmental justice. Our results indicate that a substantial proportion of all demographic groups studied live within a mile of the nearest facility, with values ranging from 22% of Whites above poverty in the Baton Rouge-New Orleans Corridor to 60% of African Americans below poverty in Baltimore. Likewise, a substantial proportion of all demographic groups also live within 2 miles of four or more industrial facilities, with values ranging from 16% for Whites above poverty in the Corridor to 70% for African Americans below poverty in Baltimore. In all three study areas, African Americans were more likely than Whites to (1) live in households with incomes below the household poverty line, (2) have children 5 years of age or younger, (3) live closer to the nearest industrial emissions source, and (4) live within 2 miles of multiple industrial emission sources. Findings indicate that, compared with White children, a substantially higher proportion of African-American children 5 years of age or younger lived in poor households that were located in relatively close proximity to one or more industrial sources of air pollution.

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.

A school-based strategy to assess children's environmental exposures and related health effects in economically disadvantaged urban neighborhoods

The School Health Initiative: Environment, Learning, Disease (SHIELD) study is a novel school-based investigation of children's environmental health in economically disadvantaged urban neighborhoods of Minneapolis. This article describes the study design and summarizes lessons learned about recruiting and monitoring this historically understudied population. The SHIELD study focused on measuring children's exposures to multiple environmental stressors [volatile organic chemicals (VOCs), environmental tobacco smoke, allergens, bioaerosols, metals, pesticides, polychlorinated biphenyls (PCB), phthalates] and exploring related effects on respiratory health (e.g., lung function) and learning outcomes (e.g., standardized test scores, academic achievement). It involved intensive exposure monitoring, including environmental measurements inside and outside the children's schools and inside their homes, personal measurements with passive dosimeters worn by the children, and biological marker measurements in blood and urine. The SHIELD participants comprised a stratified random sample of 153 "index" children and 51 of their siblings enrolled in grades 2-5 at two adjacent elementary schools. The Minneapolis Public Schools (MPS) assisted with identifying, contacting, recruiting, and monitoring this population, which traditionally is difficult to study because families/children are highly mobile, speak a diversity of languages, frequently do not have a telephone, endure economic hardships, often do not trust researchers, and have a spectrum of unconventional lifestyles and living arrangements. Using a school-based approach, the overall SHIELD enrollment (response) rate was 56.7%, with a wide disparity between English-speaking (41.7%) and non-English-speaking (71.0%) families/children. Most children remained involved in the study through both monitoring sessions and exhibited an acceptable degree of compliance with study protocols, including providing blood and urine samples. Results indicate that it is both practical and affordable to conduct probability-based exposure studies in this population, but that it is also important to improve our understanding of factors (e.g., cultural, economic, psychological, social) affecting the willingness of families/children to participate in such studies, with special emphasis on developing cost-effective recruitment methods.

Assessing children's exposure to hazardous environmental chemicals: an overview of selected research challenges and complexities

There is renewed interest in the United States regarding characterization of children's exposures to hazardous environmental chemicals. Many studies are currently underway that use novel and innovative approaches to assess childhood exposures to a variety of toxic chemicals, including both persistent and nonpersistent compounds. This article reviews some of the critical challenges that can impede scientifically rigorous studies designed to measure children's environmental exposures. The discussion briefly examines three topical areas: administrative issues (IRB approval, participant incentives, community involvement, and communication of results to research participants and stakeholders); data-collection issues (identifying and recruiting children/families, measuring actual exposures/doses); and issues related to chemical analysis of biological samples (examples of chemicals and chemical classes that can be measured in human tissue and excreta, effects of a child's age on the type and amount of biological samples available for analysis). These research complexities are discussed in the context of developing more effective and efficient exposure assessment methods.

Comparison of short-term variations (15-minute averages) in outdoor and indoor PM2.5 concentrations

Measurements of 15-min average PM2.5 concentrations were made with a real-time light-scattering instrument at both outdoor (central monitoring sites in three communities) and indoor (residential) locations over two seasons in the Minneapolis-St. Paul metropolitan area. These data are used to examine within-day variability of PM2.5 concentrations indoors and outdoors, as well as matched indoor-to-outdoor (I/O) ratios. Concurrent gravimetric measurements of 24-hr average PM2.5 concentrations were also obtained as a way to compare real-time measures with this more traditional metric. Results indicate that (1) within-day variability for both indoor and outdoor 15-min average PM2.5 concentrations was substantial and comparable in magnitude to day-to-day variability for 24-hr average concentrations; (2) some residences exhibited substantial variability in indoor aerosol characteristics from one day to the next; (3) peak values for indoor short-term (15-min) average PM2.5 concentrations routinely exceeded 24-hr average outdoor values by factors of 3-4; and (4) relatively strong correlations existed between indoor and outdoor PM2.5 concentrations for both 24-hr and 15-min averages.

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).

Pesticide storage and use patterns in Minnesota households with children

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.