EXPOSURE OF GASOLINE ROAD-TANKER DRIVERS TO METHYL TERT-BUTYL ETHER AND METHYL TERT-AMYL ETHER

Organic oxygenates, namely, methyl tert-butyl ether (MTBE) and methyl tert-amyl ether (MTAE), are added to gasoline to reduce carbon monoxid e in exhausts and to enhance the octane number. The aim of this study was to investigate road-tanker drivers' exposure to oxygenate vapors d uring road-tanker loading and unloading as well as to evaluate the mea surements of these ethers and their metabolites in the urine as a mean s of assessing the uptake of the ethers. A total of 11 drivers in diff erent parts of Finland were trained to monitor their exposure with per sonal samplers, to report their working conditions, and to collect the ir whole-day urine samples. Charcoal tubes of the air samples were ana lyzed for MTBE, MTAE, benzene, toluene, and aliphatic hydrocarbons. Fo r biological monitoring purposes the two main oxygenates, tertiary eth ers MTBE and MTAE, as well as their main metabolites, tertiary alcohol s tert-butanol (TEA) and tert-amyl alcohol (TAA), were determined in u rine specimens. On average the drivers were exposed to vapors for shor t periods (21 +/- 14 min) three times during a work shift. The mean co ncentrations of MTBE and MTAE (mean +/- SD) were 8.1 +/- 8.4 and 0.3 /- 0.4 mg/m(3). The total MTBE uptake during the shift was calculated to be an average of 106 +/- 65 mu mol. The mean concentrations of MTBE , TEA, MTAE and TAA detected in the first urine after the work shift w ere 113 +/- 76, 461 +/- 337, 16 +/- 21, and 40 +/- 38 nmol/l, and thos e found the next morning, 16 h later, were 18 +/- 12, 322 +/- 213, 9 /- 10, and 20 +/- 27 nmol/l. The good relationship (r = 0.84) found be tween MTBE exposure and postshift excretion suggests that urinary MTBE can be used for biological monitoring of exposure, but at the present low level of exposure the corresponding metabolite TEA is not equally reliable. The determination of MTAE and its metabolite TAA in urine i s sensitive enough to detect the low degree of exposure to MTAE, but i n this study the data were too scarce to allow calculation of the corr elations due to very low levels of MTAE exposure.