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

Abstract

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.

Determinants of temporal variability in NHEXAS-Maryland environmental concentrations, exposures, and biomarkers

“…Biomarkers include parent compounds and metabolites in urine or blood. Analytical results are not available for every chemical in every medium for technical and/or logistical reasons (Pang et al, 2002). This investigation concentrates on lead (PB) from the metals, phenanthrene (PHEN) from the PAHs, and chlorpyrifos (CPF) from the pesticides based on a high detection frequency in multiple media (Table 1).…”

“…Sample collection and analysis protocols varied by media, have been described elsewhere (MacIntosh et al, 1999a(MacIntosh et al, , 2001bRyan et al, 2000;Williams et al, 2001;Pang et al, 2002), and are summarized in Table 2.…”

“…Clayton et al (1999) evaluated correlations among pairs of longitudinal observations in the NHEXAS-Region 5 study and concluded that a single measurement provided a reasonable estimate of long-term exposure for some compounds (e.g., arsenic and lead in tap water) but not for others (e.g., VOCs in personal air). We followed the lead of others (Fleiss, 1986;Lemasters et al, 1996;Ryan et al, 2000;Symanski et al, 2001;Pang et al, 2002) in partitioning variance into between-and within-person components (Table 6) to evaluate the reliability of a single measurement with respect to a long-term average. The high intraclass correlation coefficient (r r ) of 0.76 for both lead in blood and chlorpyrifos in dust indicates that the observed variance was largely due to subject-specific differences and that measurements for a given individual were consistent over the study period of 1 year.…”

Pesticide loadings of select organophosphate and pyrethroid pesticides in urban public housing

“…More recently, studies have focused on urban settings and have highlighted the widespread use of pesticides indoors (Quackenboss et al, 2000;Pang et al 2002;Whyatt et al 2002;Berkowitz et al 2003).…”

Multimedia measurements and activity patterns in an observational pilot study of nine young children

“…Although recent research efforts have collected much needed data to improve our understanding of the potential exposures of young children in their homes, child care centers, and other environments (Zartarian et al, 1995(Zartarian et al, , 1997(Zartarian et al, , 1998Bradman et al, 1997Bradman et al, , 2007Byrne et al, 1998;Gurunathan et al, 1998;Landrigan et al, 1999;Adgate et al, 2000Adgate et al, , 2001Fenske et al, 2000bFenske et al, , 2002Freeman et al, 2001;Lu et al, 2001;MacIntosh et al, 2001;Pang et al, 2002;Clayton et al, 2003;Curl et al, 2003;Duggan et al, 2003;Shalat et al, 2003;Wilson et al, 2003Wilson et al, , 2004Hore et al, 2005;Morgan et al, 2005;Perera et al, 2006), it is not clear what factors most influence a child's potential exposure to pesticides.…”