An assessment of the exposure of technicians working in a chemical laboratory for aromatic hydrocarbons at Neftochim, Burgas.

The average exposure to aromatic hydrocarbons per working shift of laboratory assistants at a chemical laboratory were measured. The laboratory is one of the service departments for four different production departments at Neftochim, Burgas--the largest oil refinery in Bulgaria. Long-term sampling of the air from different workplaces in the laboratory was performed by sampling charcoal sorbent tubes (type CT-CN-2), manufactured by Higitest (type NIOSH). The concentration of benzene, toluene, ethyl benzene, xylene and isopropyl benzene in the air at the laboratory was determined by gas chromatography using the Varian MEGA 1 with a flame ionisation detector and Inowax capillary column. The measured exposure levels of toxic substances in the aromatic hydrocarbons analysis laboratory were as follows: Benzene, 0.15-1.3 mg/m3, in single samples its concentration was 4.06-8.63 mg/m3; toluene, 0.15-0.46 mg/m3, in single samples its concentration was 5.5-15.62 mg/m3; ethyl benzene in most samples was 0.02 mg/ m3, in single samples its concentration was 20.68 mg/m3; xylene in most samples was 0.4 mg/m3, in single samples its concentration was 0.51-1.68 mg/m3; isopropyl benzene in most samples was 0.1 mg/m3, in single samples its concentration was 0.20-1.12 mg/m3. The results, obtained by measuring the average work-shift exposure of laboratory assistants to aromatic hydrocarbons in the air at the analytical laboratories, show that the measured concentrations are smaller than the respective threshold limit values. Bearing in mind, however, that some of these substances have an effect on the human organism, exposure to them is excessively hazardous for laboratory technicians.