Environmental and biological monitoring of benzene during self-service automobile refueling

Although automobile refueling represents the major source of benzene exposu re among the non-smoking public, few data are available regarding such expo sures and the associated uptake of benzene. We repeatedly measured benzene exposure and uptake (via benzene in exhaled breath) among 39 self-service c ustomers using self-administered monitoring, a technique rarely used to obt ain measurements from the general public (130 sets of measurements were obt ained). Benzene exposures averaged 2.9 mg/m(3) (SD = 5.8 mg/m(3); median du ration = 3 min) with a range of < 0.076-36 mg/m(3), and postexposure breath levels averaged 160 <mu>g/m(3) (SD = 260 mug/m(3)) with a range of < 3.2-1 ,400 <mu>g/m(3). Log-transformed exposures and breath levels were significa ntly correlated (r = 0.77, p < 0.0001). We used mixed-effects statistical m odels to gauge the relative influences of environmental and subject-specifi c factors on benzene exposure and breath levels and to investigate the impo rtance of various covariates obtained by questionnaire. Model fitting yield ed three significant predictors of benzene exposure, namely, fuel octane gr ade (p = 0.0011), duration of exposure (p = 0.0054), and season of the year (p = 0.032). Likewise, another model yielded three significant predictors of benzene concentration in breath, specifically, benzene exposure (p = 0.0 001), preexposure breath concentration (p = 0.0008), and duration of exposu re (p = 0.038). Variability in benzene concentrations was remarkable, with 95% of the estimated values falling within a 274-fold range, and was compri sed entirely of the within-person component of variance (representing expos ures of the same subject at different times of refueling). The correspondin g range for benzene concentrations in breath was 41-fold and was comprised primarily of the within-person variance component (74% of the total varianc e). Our results indicate that environmental rather than interindividual dif ferences are primarily responsible for benzene exposure and uptake during a utomobile refueling. The study also demonstrates that self-administered mon itoring can be efficiently used to measure environmental exposures and biom arkers among the general public.