The Efficiency of Respiratory Protective Equipment Based on Monitoring a Biological Indicator, Urinary Ortho-Cresol, in Workers Exposed to Toluene

In most industries, including paint manufacturing, workers are exposed to toluene. Absorbed toluene in liver is metabolized and is exerted as urine metabolites, such as ortho-cresol. Due to different reasons, the only possible way to reduce exposure in some industries is using personal protective equipments. This study uses urine biological monitoring to examine the efficiency of a respiratory protective equipment in toluene exposure reduction among workers. Production line workers of three paint industries (22 Subjects) were studied. When the workers were not using respiratory protective equipment, their average respiratory exposure to toluene was measured during a shift. The next day, the average toluene respiratory exposure of the same workers during a shift was measured while they were using air purifying respirator masks with A1/organic vapor filters. In addition, their urine samples, collected at the end of the shifts, were sent to the lab for determining the amount of ortho-cresol. Urinary ortho-cresol measurement was carried out by NIOSH 8305. Sampling and measuring of existing toluene in workplace air was done by NIOSH 1501. No statistically significant difference was observed between the average toluene exposure levels on the first and second days (P = 0.026). However, the average respiratory toluene calculated by a formula based on urinary ortho-cresol revealed a significant difference between the two days (P < 0.05). Using related formulas and considering a 20% reduction in inhaled toluene, the average efficiency of respirator was found to be 42.6% with a protective factor of 1.7. According to NIOSH standard, protective factor for the respirators used should be 10. So, according to our results, this kind of respirator does not have sufficient efficiency for reducing toluene exposure and it cannot be used as a safe way for protecting workers against chemical pollutants.