Crotonaldehyde exposure in U.S. tobacco smokers and nonsmokers: NHANES 2005-2006 and 2011-2012

Abstract

Introduction: Crotonaldehyde is an α,β-unsaturated carbonyl compound that is a potent eye, respiratory, and skin irritant. Crotonaldehyde is a major constituent of tobacco smoke and its exposure can be quantified using its urinary metabolite N-acetyl-S-(3-hydroxypropyl-1-methyl)-L-cysteine (HPMM). A large-scale biomonitoring study is needed to determine HPMM levels, as a measure of crotonaldehyde exposure, in the general U.S.

Materials and methods: Urine samples were obtained as part of the National Health and Nutrition Examination Survey 2005-2006 and 2011-2012 from participants who were at least six-years-old (N = 4692). Samples were analyzed for HPMM using ultra performance liquid chromatography - tandem mass spectrometry. Exclusive tobacco smokers were distinguished from non- tobacco users through a combination of self-reporting and serum cotinine data.

Results: Detection rate of HPMM among eligible samples was 99.9%. Sample-weighted, median urinary HPMM levels for smokers and non-users were 1.61 and 0.313 mg/g creatinine, respectively. Multivariable regression analysis among smokers showed that HPMM was positively associated with serum cotinine, after controlling for survey year, urinary creatinine, age, sex, race, poverty level, body mass index, pre-exam fasting time, and food intake. Other significant predictors of urinary HPMM include sex (female > male), age (children > non-user adults), race (non-Hispanic Blacks < non-Hispanic Whites).

Conclusions: This study characterizes U.S. population exposure to crotonaldehyde and confirms that tobacco smoke is a major exposure source. Urinary HPMM levels were significantly higher among exclusive combusted tobacco users compared to non-users, and serum cotinine and cigarettes per day were significant predictors of increased urinary HPMM. This study also found that sex, age, ethnicity, pre-exam fasting time, and fruit consumption are related to urinary HPMM levels.

Keywords: Biomonitoring; Crotonaldehyde; HPMM; NHANES; Tobacco smoke exposure.

Fig. 1

Percentage distribution (not sample-weighted) of urinary HPMM concentrations (μg/g creatinine) among non-users and exclusive combusted tobacco users. Urinary HPMM concentration data were log (base 10) transformed.

Fig. 2

Least-square means of urinary HPMM concentrations for different numbers of cigarettes smoked per day (CPD) categories, adjusted for all other regression variables (e.g., age, sex, race/ethnicity, etc.).

Fig. 3

Scatterplot diagrams showing correlations between HPMA and HPMM (a) & CEMA and HPMM (b). Data were adjusted for urinary creatinine and log (base 10) transformed.