Car Air Fresheners as a Source of Ethnic Differences in Exposure to 1,4-Dichlorobenzene

Abstract

To the Editor: 1,4-Dichlorobenzene (1,4-DCB) is a volatile organic compound used in mothballs and some air fresheners, and a common contaminant of indoor air. It has been classified as a possible carcinogen1 and may be related to decreased pulmonary function in adults.2 According to data from the National Health and Nutrition Examination Surveys (NHANES), personal exposure to 1,4-DCB is higher for nonwhites than for whites, measured both in blood and air.3–5 This difference is not explained by self-reported exposures. In the 1999–2000 NHANES survey, 4% of participants with personal 1,4-DCB measurements reported recent exposure to mothballs, while 50% reported recent exposure to air fresheners3; the frequency of self-reported exposure did not differ by race. It is possible that whites and nonwhites select different products or use them in different ways, contributing to variation in measured exposures to 1,4-DCB. Air fresheners used in vehicles are one group of products that may contribute to increased exposures to 1,4-DCB and other volatile organic compounds. Although air fresheners come in a variety of forms, a common type used in vehicles is an odorant-impregnated paper cutout that hangs from the rear view mirror. In this location, the scent-producing compounds may be volatilized by exposure to sunlight or warm air from the vehicle's defroster, and closed windows may lead to further increases in concentration. We conducted a case-control study to assess the possibility that the presence of air fresheners in motor vehicles varies by race. We collected data while traveling on US Interstate Highways 40 (I-40) and 85 (I-85) between Raleigh and Winston-Salem, North Carolina, on 2 consecutive weekends in March 2006 and also in May 2006. Eligible participants included all motor vehicles traveling in the same direction that passed our car or were passed by us. Each vehicle with at least one air freshener hanging from the rear view mirror was considered a “case,” while the next passing or passed vehicle without an air freshener was considered a “control.” Information on the driver's apparent race (white vs. nonwhite, based on skin color, facial features, and hair) and sex was collected for all cases and controls. During the approximate 8-hour study period, 81 vehicles with air fresheners (“cases”) were observed. The odds of a nonwhite driver having an air freshener was 7.8 (95% confidence interval = 3.9–16) (Table 1). The majority of the air fresheners were shaped like pine trees or leaves.TABLE 1: Distribution of Apparent Race and Sex for Drivers of Vehicles With and Without Air Fresheners, US Interstate Highways 40 and 85, North Carolina, 2006Our observation that air fresheners are more common in vehicles driven by nonwhites suggests that ethnic differences in exposure to 1,4-DCB may be explained in part by use of these products. The question in NHANES about recent exposure to air fresheners does not differentiate between household and vehicle use, and the exposures to 1,4-DCB at home and in cars may be different. The classification of race-ethnicity is a limitation of this study. Self-report is generally preferred, but was not possible with our sampling approach. We may have failed to identify air fresheners in some vehicles, although under-ascertainment of cases is unlikely to be related to race. We also could not determine whether the air fresheners we observed contained 1,4-DCB. However, laboratory analysis of representative car air fresheners confirmed the presence of this compound (data not shown). The widespread use of these products suggests that quantitative levels of volatile organic compounds from air fresheners in vehicles is worth investigating. Leslie Elliott Washoe County District Health Department Reno, NV [email protected] Dana Loomis Department of Environmental and Occupational Health School of Public Health University of Nevada Reno, NV