Abstract
A total of 29 tank cleaners and 31 referent controls participated in the study. In most cases, the tank cleaners were employed in small companies, usually specialized subcontractors such as firms only working in refineries cleaning oil tanks and handling oil spills. The air concentrations of hydrocarbons (HCs) in tanks containing residuals from heavy fuel oil were generally low, unless the oil was still warm. Addition of light fuel oil to facilitate the cleaning of tanks containing viscous, heavy fuel oils resulted in total airborne HC levels of 1000–1500 mg/m3 High levels of HC were measured in tanks with low-boiling petroleum fractions (naphtha and light fuel oils) of 1000–2600 mg/m3 (maximum). Today, most cleaners use air-supplied respirators or air-purifying respirator cartridges inside tanks with petroleum products or other chemicals. The exception is small firms handling fuel oils for heating purposes where only 50% of the workers use protective equipment regularly; the other workers only occasionally use protective equipment even if the air concentrations of HC are high. Protective equipment is rarely used in small, domestic tanks. Measurements of heart rate showed that tank cleaning is, at times, a highly strenuous job. No differences between tank cleaners and controls were found with respect to spirometry, liver enzymes, or frequency of micronuclei. Acute intoxications were not frequently reported in this group. However, this investigation may underestimate the true risk, as it is a cross-sectional study that found that exposures were highly variable, both quantitively and qualitatively. In many cases, the tank cleaners knew very little about the potential hazards or the proper use of protective equipment. Implementation of training programs, protective equipment, better ventilation, and more automated cleaning techniques are needed. Medical attention and industrial hygiene surveillance of these workers is also recommended.