EXPOSURE TO METHYL TERT-BUTYL ETHER AND TERT-AMYL METHYL-ETHER FROM GASOLINE DURING TANK LORRY LOADING AND ITS MEASUREMENT USING BIOLOGICALMONITORING

Objective and methods: The exposure of Finnish tank lorry drivers to m ethyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) during loading of gasoline was studied using biological and breathing-zone s ampling. During the field measurements - in October 1994 and august 19 95 - the gasolines (95, 98, 99 RON) contained MTBE to 5.2-11.8% and TA ME to 0-6%. Results: The geometric mean (GM) breathing-zone concentrat ion of MTBE was 4.3 mg/m(3) (n = 15) in October and 6.4 mg/m(3) (n = 2 0) in August. The GM concentration of TAME, measured only in August, w as 0.98 mg/m(3). The mean loading/sampling times were 37 and 35 min, t he mean wind speeds were 0.8 and 0.6 m/s, and the mean air temperature s were -4.9 degrees and +14.1 degrees C, respectively. Blood samples c ollected on average at 20 min after gasoline loading/exposure showed a n MTBE concentration of 143 nmol/l (GM, n = 14) in October and 213 nmo l/l (GM, n = 20) in August. Pearson's coefficient of correlation (r) b etween the MTBE breathing-zone concentrations and MTBE in blood was 0. 86 (P = 0.0001) in October and 0.81 (P = 0.00001) in August. No correl ation was found between MTBE in air and the metabolite tertbutanol (TB A) in blood. MTBE, but not TEA, in urine samples collected on average at 2.5 h after exposure showed a correlation with MTBE in air. The con centrations of TAME and its metabolite tert-amyl alcohol were below th e quantitation limits (<7 and <100 nmol/l, respectively) in most blood and urine samples. Conclusions: The breathing-zone measurements showe d low levels of exposure to the two oxygenates, the concentrations bei ng well below the current hygienic standards for MTBE (250-360 mg/m(3) for 15 min and 90-180 mg/m(3) for 8 h). The linear correlations obtai ned for MTBE suggest that MTBE in blood or urine can be adopted as a v alid biological exposure index.