%0 Journal Article
%T Carpet-dust chemicals as measures of exposure: Implications of variability
%A Todd P Whitehead
%A John R Nuckols
%A Mary H Ward
%A Stephen M Rappaport
%J Emerging Themes in Epidemiology
%D 2012
%I BioMed Central
%R 10.1186/1742-7622-9-2
%X We analyzed 9 polycyclic aromatic hydrocarbons, 6 polychlorinated biphenyls, and nicotine in 68 carpet-dust samples from 21 households in agricultural communities of Fresno County, California collected from 2003-2005. Chemical concentrations (ng per g dust) ranged from < 2-3,609 for 9 polycyclic aromatic hydrocarbons, from < 1-150 for 6 polychlorinated biphenyls, and from < 20-7,776 for nicotine. We used random-effects models to estimate variance components for concentrations of each of these carpet-dust chemicals and calculated the variance ratio, ¦Ë, defined as the ratio of the within-household variance component to the between-household variance component. Subsequently, we used the variance ratios calculated from our data, to illustrate the potential effect of measurement error on the attenuation of odds ratios in hypothetical case-control studies. We found that the median value of the estimated variance ratios was 0.33 (range: 0.13-0.72). Correspondingly, in case-control studies of associations between these carpet-dust chemicals and disease, given the collection of only one measurement per household and a hypothetical odds ratio of 1.5, we expect that the observed odds ratios would range from 1.27 to 1.43. Moreover, for each of the chemicals analyzed, the collection of three repeated dust samples would limit the expected magnitude of odds ratio attenuation to less than 20%.Our findings suggest that attenuation bias should be relatively modest when using these semi-volatile carpet-dust chemicals as exposure surrogates in epidemiologic studies.Semi-volatile chemicals can accumulate in carpets over years and decades [1-3], and thus their concentrations in carpet dust could be useful surrogates for long-term indoor exposures in epidemiological studies [2,4-6]. Moreover, because dust ingestion or inhalation could be responsible for significant chemical exposures in young children [7-9], levels of chemicals in dust may be particularly relevant in studies of childhood
%U http://www.ete-online.com/content/9/1/2