Urinary methyl tert-butyl ether and benzene as biomarkers of exposure to urban traffic.

Methyl tert-butyl ether (MTBE) and benzene are added to gasoline to improve the combustion process and are found in the urban environment as a consequence of vehicular traffic. Herein we evaluate urinary MTBE (MTBE-U) and benzene (BEN-U) as biomarkers of exposure to urban traffic. Milan urban policemen (130 total) were investigated in May, July, October, and December for a total of 171 work shifts. Personal exposure to airborne benzene and carbon monoxide (CO), and atmospheric data, were measured during the work shift, while personal characteristics were collected by a questionnaire. A time/activity diary was completed by each subject during the work shift. Spot urine samples were obtained for the determination of MTBE-U and BEN-U. Median personal exposure to CO and airborne benzene were 3.3 mg/m(3) and 9.6 µg/m(3), respectively; median urinary levels in end-of-shift (ES) samples were 147 ng/L (MTBE-U) and 207 ng/L (BEN-U). The time spent on traffic duty at crossing was about 40% of work time. Multiple linear regression models, taking into account within-subject correlations, were applied to investigate the role of urban pollution, atmospheric conditions, job variables and personal characteristics on the level of biomarkers. MTBE-U was influenced by the month of sampling and positively correlated to the time spent in traffic guarding, CO exposure and atmospheric pressure, while negatively correlated to wind speed (R(2) for total model 0.63, P<0.001). BEN-U was influenced by the month and smoking habit, and positively correlated to urinary creatinine; moreover, an interaction between CO and smoking was found (R(2)=0.62, P<0.001). These results suggest that MTBE-U is a reliable marker for assessing urban traffic exposure, while BEN-U is determined mainly by personal characteristics.

Determination of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in human urine by HS-SPME gas chromatography/mass spectrometry.

Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/polydimethylsiloxane, polydimethylsiloxane/divinylbenzene, and polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30-4600 ng L(-1), within- and between-run precision, as coefficient of variation, <22 and <16%, accuracy within 20% the theoretical level, and limit of detection of 6 ng L(-1) for all the analytes. The influence of the matrix on the quantification of these ethers was evaluated analysing the specimens of seven traffic policemen exposed to autovehicular emissions: using the calibration curve and the method of standard additions comparable levels of MTBE (68-528 ng L(-1)), ETBE (<6 ng L(-1)), and TAME (<6 ng L(-1)) were obtained.

Comparison between urinary o-cresol and toluene as biomarkers of toluene exposure.

The characteristics of urinary o-cresol (o-C) and urinary toluene (TOL-U) as biomarkers of occupational exposure to toluene were comparatively evaluated. One hundred healthy male rotogravure printing workers and 161 male and female control subjects were studied. Personal exposure to airborne toluene (TOL-A) during the shift was determined as a time-weighted average. Simple analytical procedures based on solid phase microextraction followed by gas chromatography/mass spectometry analysis were applied to the determination of end-shift o-C and TOL-U. Median TOL-A was 48 (6.0-162.0) mg/m3 in printers and 0.021 (<0.003-0.137) mg/m3 in controls. o-C was 0.185 (0.032-0.948) mg/g creatinine in printers and 0.027 (<0.006-0.330) mg/g creatinine in the controls. TOL-U was 7.6 (1.8-23.9) microg/L in printers and 0.140 (0.094-0.593) microg/L in the controls. According to all indices, exposure to toluene was higher in printers than in the controls. Nevertheless, the distribution of o-C in the two groups partially overlapped, whereas such behavior was not found in TOL-U. Both o-C and TOL-U in printers were correlated with TOL-A (Pearson's on log10-transformed variables r = 0.704 and 0.844, respectively) and with each other (r = 0.683). Smoking habits significantly increased the excretion of o-C but not of TOL-U. From the point of view of sampling conditions and analytical requirements, TOL-U and o-C showed similar properties, but comparison of their intrinsic characteristics showed that TOL-U had higher specificity and sensitivity, lower background values, was better correlated with airborne exposure, and was not influenced by cigarette smoking. Therefore TOL-U may be considered superior to o-C as a biomarker of occupational exposure to toluene.

Biological monitoring of exposure to polycyclic aromatic hydrocarbons by determination of unmetabolized compounds in urine.

In this paper we evaluated the possibility to assess occupational exposure to polycyclic aromatic hydrocarbons (PAHs) measuring unmetabolized PAHs in urine. With this aim, 24 road paving (RP) workers, exposed to bitumen fumes, and 6 road construction workers (CW), exposed to diesel exhausts, were investigated. Median personal exposure to low boiling PAHs (from naphthalene to pyrene) during the work shift ranged from 0.5 to 369 ng/m(3), with naphthalene as the most abundant compound. Three urine samples were collected for each worker: baseline (after 2 days of vacation), before- and end-shift samples (in the second part of the work week). The following urinary compounds were measured by headspace-solid phase microextraction GC/MS: naphthalene (U-NAP), acenaphthylene (U-ACY), acenaphthene (U-ACE), fluorene (U-FLE), phenanthrene (U-PHE), anthracene (U-ANT), fluoranthene (U-FLU), pyrene (U-PYR). Urinary PAHs were detected in almost all samples. Median levels for U-NAP, U-PHE, U-PYR and U-FLE in end-shift samples were 82, 48, 54 and 21 ng/L in RP and 69, 14, 24 and 15 ng/L in CW, respectively. Significant differences in the levels of U-PHE, U-FLU and U-PYR were found between RP and CW (p<0.05). Moreover in RP samples the urinary excretion of most analytes increased during the work shift (p<0.05). These results suggest that urinary PAHs may be useful biomarkers of occupational exposure.

Determination of urinary ortho- and meta-cresol in humans by headspace SPME gas chromatography/mass spectrometry.

ortho-Cresol (o-C) and meta-cresol (m-C) are minor urinary metabolites of toluene, a widely used chemical with neurotoxicological properties. A new assay for their determination in human urine is here proposed. Urinary cresol sulphates and glucuronates are submitted to acid hydrolysis, urine is neutralized, added with o-cresols-d8, and analytes are sampled in the headspace of urine by SPME using a polydimethylsiloxane fiber. Analysis is performed by GC/MS using, for separation, either a SupelcoWax10 (for o-C) or a chiral CP Cresol (for o-C and m-C) column. The method is very specific, with a range of linearity 0-5.0 mg/l, within- and between-run precision, as coefficient of variation, <15% and <19%, limit of detection of 0.006 mg/l for o-C and 0.007 mg/l for m-C. The procedure is applied to the quantification of cresols in urine from workers exposed to toluene and from subjects belonging to the general population.