Article pubs.acs.org/est
Environmental Determinants of Polychlorinated Biphenyl Concentrations in Residential Carpet Dust Curt T. DellaValle,*,† David C. Wheeler,‡ Nicole C. Deziel,† Anneclaire J. De Roos,§ James R. Cerhan,∥ Wendy Cozen,⊥ Richard K. Severson,# Abigail R. Flory,▽ Sarah J. Locke,† Joanne S. Colt,† Patricia Hartge,○ and Mary H. Ward† †
Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-5465, United States ‡ Department of Biostatistics, Virginia Commonwealth University, Richmond, Virginia 23219, United States § Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, United States ∥ Division of Epidemiology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, United States ⊥ University of Southern California, Los Angeles, California 90089, United States # Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, Michigan 48201, United States ▽ Westat Corporation, Rockville, Maryland 20850, United States ○ Biostatistics Branch , Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, 20892-5465, United States S Supporting Information *
ABSTRACT: Polychlorinated biphenyls (PCBs), banned in the United Sates in the late 1970s, are still found in indoor and outdoor environments. Little is known about the determinants of PCB levels in homes. We measured concentrations of five PCB congeners (105, 138, 153, 170, and 180) in carpet dust collected between 1998 and 2000 from 1187 homes in four sites: Detroit, Iowa, Los Angeles, and Seattle. Home characteristics, occupational history, and demographic information were obtained by interview. We used a geographic information system to geocode addresses and determine distances to the nearest major road, freight route, and railroad; percentage of developed land; number of industrial facilities within 2 km of residences; and population density. Ordinal logistic regression was used to estimate the associations between the covariates of interest and the odds of PCB detection in each site separately. Total PCB levels [all congeners < maximum practical quantitation limit (MPQL) vs at least one congener ≥ MPQL to < median concentration vs at least one congener > median concentration] were positively associated with either percentage of developed land [odds ratio (OR) range 1.01−1.04 for each percentage increase] or population density (OR 1.08 for every 1000/mi2) in each site. The number of industrial facilities within 2 km of a home was associated with PCB concentrations; however, facility type and direction of the association varied by site. Our findings suggest that outdoor sources of PCBs may be significant determinants of indoor concentrations.
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INTRODUCTION Polychlorinated biphenyls (PCBs) are manmade compounds found in older electrical equipment, hydraulic machinery, fluorescent lighting fixtures, and numerous construction materials such as plasticizers, adhesives, flame retardants, caulk, and paints.1−3 Ecological concerns, the probable carcinogenicity of PCBs,4 and links to diseases of the immune, reproductive, nervous, and endocrine systems led to the banning of manufacturing and use of PCBs in the United States in 1977 and 1979, respectively.3 However, PCBs remain environmental contaminants due to their persistence and bioaccumulation through the food chain. PCBs are found in many older buildings and can persist for long periods of time indoors because they are not susceptible to environmental and microbial degradation.5,6 In fact, despite cessation of use for © 2013 American Chemical Society
several decades, there has been little change in PCB concentrations in indoor air, where levels can be approximately 30 times higher than in ambient air.7 These findings are important given that people of all ages spend up to 90% of their time indoors.8,9 A recent study of 24 schools, residences, and other public use buildings in the Boston area found that 33% contained caulking material with PCB content exceeding 50 parts per million (ppm),10 the established U.S. Environmental Protection Agency (EPA) limit for PCBs in construction materials and Received: Revised: Accepted: Published: 10405
April 4, 2013 July 15, 2013 August 16, 2013 August 16, 2013 dx.doi.org/10.1021/es401447w | Environ. Sci. Technol. 2013, 47, 10405−10414
Environmental Science & Technology
Article
other nonliquid products. The breakdown of construction materials, especially in buildings constructed in the middle part of the 20th century, in which PCB concentrations were found to be highest,2,5,11 may act as a source of PCB emissions to indoor and ambient environments. While many sources of PCBs in the indoor environment have been identified, characterization of these sources remains incomplete.12 Many studies have found higher atmospheric and soil PCB levels associated with greater proximity to urban centers, particularly industrial complexes.13−22 Specifically, industrial complexes such as waste facilities, coal-fired power plants, and various types of incinerators have been identified as PCB sources in the United States20 and worldwide.21,23−26 Electrical and power equipment, hydraulic machinery, and other materials that may contain PCBs are also found along roads and within railyards, which have been identified as areas with PCB contamination.27 In addition, roads may facilitate PCB dispersion by serving as corridors for transportation of contaminated soils by wind.28 Soils act as a major reservoir and sink for many persistent organic pollutants (POPs), including PCBs.29 Therefore, soil−air exchange processes, such as deposition and volatilization, may also be relevant to the movement of PCBs in the environment.14 PCBs persist in carpet dust due to their resistance to degradation, semivolatile nature, and high propensity to bind to particles.29−31 Levels in carpet dust may therefore be a good measure of long-term indoor exposure.30,32 Specifically, ingestion and inhalation of carpet dust may represent relevant exposure pathways.33 House dust may also be an especially important source of exposure for small children as it represents a greater proportion of overall PCB exposure in toddlers (6−24 months) than adults.33 When carpet dust was used as an exposure metric, higher PCB concentrations were associated with an increased risk of non-Hodgkin lymphoma (NHL) in the National Cancer Institute’s (NCI) Surveillance, Epidemiology and End Results (SEER) NHL case-control study.2 In light of the potential health risks associated with PCBs and the importance of dust as an exposure pathway, we sought to identify home and community characteristics, demographic, and environmental factors that may be determinants of PCB levels in carpet dust samples collected in the NCI SEER-NHL study.
subjects review boards at all participating institutions, and written informed consent was obtained from each participant. Computer-assisted personal interviews were conducted in each participant’s home. Interviewers asked about housing type, age of the home, number of rooms that were usually vacuumed with the sampled vacuum cleaner, and presence of Oriental rugs. Complete occupational histories and demographic information on race and education were also obtained. Dust Samples and Laboratory Analysis. As described in detail previously,2,34 dust was collected between February 1999 and May 2001 from vacuum cleaners of participants who gave permission (93% of cases, 95% of controls) and who had used their vacuum cleaner within the past year and owned at least half their carpets or rugs for 5 years or more [695 cases (57%), 521 controls (52%)]. Dust samples from 682 cases (98%) and 513 controls (98%) were successfully analyzed between September 1999 and September 2001. We analyzed 2 g dust aliquots for five PCB congeners (105, 138, 153, 170, and 180) using gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode; concentrations were quantified via the internal standard method. The congeners were chosen because they are among the most commonly detected in house dust.36 The usual detection limit (UDL) was 20.8 ng/g, although samples weighing
