Urinary biomonitoring of subjects with different smoking habits. Part II: an untargeted metabolomic approach and the comparison with the targeted measurement of mercapturic acids.

BACKGROUND: Although thousands of different chemicals have been identified in cigarette smoke, the characterization of their urinary metabolites still requires significant research. The aim of this work was to perform an untargeted metabolomic approach to a pilot cross-sectional study conducted on subjects with different smoking habits and to compare the results with those of the targeted measurement of mercapturic acids. METHODS: Urine samples from 67 adults, including 38 non-smokers, 7 electronic cigarette users, and 22 traditional tobacco smokers were collected. Samples were analysed by liquid chromatography/time-of flight mass spectrometry. Data were processed using the R-packages IPO and XCMS to perform feature detection, retention time correction and alignment. One-way ANOVA test was used to identify different features among groups. Quantitative determination of 17 mercapturic acids was available from a previous study. RESULTS: One hundred and seventeen features, out of 3613, were different among groups. They corresponded to 91 potential metabolites, 5 of which were identified vs authentic standards, 43 were putatively annotated and 13 were attributed to chemical classes. Among identified compounds there were the mercapturic acids of acrolein, 1,3-butadiene, and crotonaldehyde; among putatively annotated compounds there were the glucuronide conjugated of 3-hydroxycotinine and the sulfate conjugate of methoxyphenol; with the lowest degree of confidence several sulfate conjugates of small molecules were annotated. Considering mercapturic acids, the coherence between the targeted and untargeted approach was found for a limited number of chemicals, typically the most abundant. CONCLUSIONS: Differences in the urinary levels of several compounds were associated to the different smoking habits, suggesting that the proposed approach is useful for the investigation of the metabolite patterns related to the exposure to toxicants. However, limitations were highlighted, in particular regarding the identification of low concentration compounds.

Urinary biomonitoring of subjects with different smoking habits. Part I: Profiling mercapturic acids.

BACKGROUND: While tobacco smoke contains thousands of chemicals, some of which are carcinogenic to humans, the content of electronic cigarette smoke is less known. This work aimed to assess and compare the exposure associated with different smoking habits by profiling urinary mercapturic acids as biomarkers of toxic compounds. METHODS: In this pilot study, sixty-seven healthy adults with different smoking habits were investigated: 38 non-smokers (NS), 7 electronic cigarette users (ECU), and 22 traditional tobacco smokers (TTS). Seventeen urinary mercapturic acids, metabolites of 1,3-butadiene (DHBMA, MHBMA), 4-chloronitrobenze (NANPC), acrolein (3-HPMA), acrylamide (AAMA, GAMA), acrylonitrile (CEMA), benzene (SPMA), crotonaldehyde (CMEMA, HMPMA), ethylating agents (EMA), methylating agents (MMA), ethylene oxide (HEMA), N,N-dimethylformamide (AMCC), propylene oxide (2-HPMA), styrene (PHEMA), and toluene (SBMA), were quantified, along with urinary nicotine and cotinine. RESULTS: Median urinary cotinine was 0.4, 1530 and 1772 µg/L in NS, ECU and TTS, respectively. Most mercapturic acids were 2-165 fold-higher in TTS compared to NS, with CEMA, MHBMA, 3-HPMA and SPMA showing the most relevant increases. Furthermore, some mercapturic acids were higher in ECU than NS; CEMA and 3-HPMA, in particular, showed significant increases and were 1.8 and 4.9 fold-higher, respectively. CONCLUSIONS: This study confirms that tobacco smoking is a major source of carcinogenic chemicals such as benzene and 1,3-butadiene; electronic cigarette use is a minor source, mostly associated with exposure to chemicals with less carcinogenic potential such as acrylonitrile and acrolein.

An LC-MS/MS method to profile urinary mercapturic acids, metabolites of electrophilic intermediates of occupational and environmental toxicants.

INTRODUCTION: Mercapturic acids are urinary metabolites of occupational and environmental toxicants. The aim of this work was to develop and validate an analytical assay for the determination of several urinary mercapturic acids to be used as biomarkers of exposure. METHOD: An isotope dilution tandem mass spectrometric method, coupled with reversed-phase liquid chromatography, was developed for the analysis of mercapturic acids derived from several compounds, including those of benzene, toluene, 1,3-butadiene, styrene, acrylonitrile, 4-chloronitrobenzene, acrylamide, acrolein, propylene oxide, N,N-dimethylformamide, crotonaldehyde, ethylene oxide, and methylating and ethylating agents. Samples were prepared by simple filtration after dilution. A validation was carried out, including the assessment of calibration curves, sensitivity, accuracy, precision, process efficiency, and stability, along with external verification. The assay was applied to the analysis of 14 end-of-shift urine samples from unexposed workers and gasoline station attendants. RESULTS: The chromatographic run lasted 18 min. Limits of quantitation ranged from 0.01 to 3.2 µg/L; precision, expressed as relative standard deviation, ranged from 0.6 to 20.9%; and accuracy ranged from 93.4 to 114.9% of theoretical values. The use of deuterated internal standards was suitable for control of the matrix effect. The assay allowed the simultaneous quantitation of urinary mercapturic acids at different concentration ranges. The external verification exercise produced good results. The application of the assay to urine samples from workers revealed differences in mercapturic acid profiles in agreement with the expected patterns of exposure. CONCLUSION: This high-throughput method is valid and useful for the quantitation of urinary mercapturic acids, and is suitable for human biomonitoring of occupational and environmental exposure.