Exposure to methyl tert-butyl ether and tert-amyl methyl ether from gasoline during tank lorry loading and its measurement using biological monitoring

Abstract

Objective and methods: The exposure of Finnish tank lorry drivers to methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME) during loading of gasoline was studied using biological and breathing-zone sampling. During the field measurements – in October 1994 and August 1995 – the gasolines (95, 98, 99 RON) contained MTBE to 5.2–11.8% and TAME to 0–6%. Results: The geometric mean (GM) breathing-zone concentration of MTBE was 4.3 mg/m³ (n= 15) in October and 6.4 mg/m³ (n= 20) in August. The GM concentration of TAME, measured only in August, was 0.98 mg/m³. The mean loading/sampling times were 37 and 35 min, the mean wind speeds were 0.8 and 0.6 m/s, and the mean air temperatures were −4.9° and +14.1 °C, respectively. Blood samples collected on average at 20 min after gasoline loading/exposure showed an MTBE concentration of 143 nmol/l (GM, n= 14) in October and 213 nmol/l (GM, n= 20) in August. Pearson's coefficient of correlation (r) between 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 correlation was found between MTBE in air and the metabolite tert-butanol (TBA) in blood. MTBE, but not TBA, in urine samples collected on average at 2.5 h after exposure showed a correlation with MTBE in air. The concentrations of TAME and its metabolite tert-amyl alcohol were below the quantitation limits (<7 and <100 nmol/l, respectively) in most blood and urine samples. Conclusions: The breathing-zone measurements showed low levels of exposure to the two oxygenates, the concentrations being well below the current hygienic standards for MTBE (250–360 mg/m³ for 15 min and 90–180 mg/m³ for 8 h). The linear correlations obtained for MTBE suggest that MTBE in blood or urine can be adopted as a valid biological exposure index.