1. ^aDepartment of Environmental and Occupational Health, School of Public Health, University of North Texas Health Science Center, Fort Worth, Texas, USA
2. ^bUS Environmental Protection Agency, National Exposure Research Laboratory, Human Exposure and Atmospheric Sciences Division, Research Triangle Park, North Carolina, USA
3. ^cDivision of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California, USA

Correspondence: Professor S.M. Rappaport, Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Mail Code 7360, Berkeley, California 94720, USA. Tel.: +1 510 642 4355; Fax: +1 510 642 5815; E-mail: srappaport@berkeley.edu

Received 9 May 2007; Accepted 29 August 2007; Published online 5 December 2007.

Abstract

The relationships between levels of volatile organic compounds (VOCs) in blood and air have not been well characterized in the general population where exposure concentrations are generally at parts per billion levels. This study investigates relationships between the levels of nine VOCs, namely, benzene, chloroform, 1,4-dichlorobenzene, ethylbenzene, methyl tert-butyl ether (MTBE), tetrachloroethene, toluene, and m-/p- and o-xylene, in blood and air from a stratified random sample of the general US population. We used data collected from 354 participants, including 89 smokers and 265 nonsmokers, aged 20–59 years, who provided samples of blood and air in the National Health and Nutrition Examination Survey (NHANES) 1999–2000. Demographic and physiological characteristics were obtained from self-reported information; smoking status was determined from levels of serum cotinine. Multiple linear regression models were used to investigate the relationships between VOC levels in air and blood, while adjusting for effects of smoking and demographic factors. Although levels of VOCs in blood were positively correlated with the corresponding air levels, the strength of association (R²) varied from 0.02 (ethylbenzene) to 0.68 (1,4-DCB). Also the blood–air relationships of benzene, toluene, ethylbenzene, and the xylenes (BTEX) were influenced by smoking, exposure–smoking interactions, and by gender, age, and BMI, whereas those of the other VOCs were not. Interestingly, the particular exposure–smoking interaction for benzene was different from those for toluene, ethylbenzene, and the xylenes. Whereas smokers retained more benzene in their blood at increasing exposure levels, they retained less toluene, ethylbenzene, and xylenes at increasing exposure levels. Investigators should consider interaction effects of exposure levels and smoking when exploring the blood–air relationships of the BTEX compounds in the general population.