Résumé
The aim of this cross-sectional study was to explore the association of crystalline silica aerosols exposure with malondialdehyde in blood serum and urinary neopterin and explore their potential as biomarkers of their external exposure. Nonsmoking and healthy male glass sandblasters and control population were randomly selected for this study. All groups were monitored for their personal exposure to crystalline silica according to NOISH method No. 7601. High Performance Liquid Chromatography [HPLC] was used to for analysis of malondialdehyde of blood serum and urinary neopterin, and creatinine in all study participants. The mean of personal exposure to crystalline silica aerosols in glass sanbalsters was 164 microg/m3 [SD: 112] compared with less than 0.006 mg/m3 for control group that was even below detection limit. The mean of blood serum malondialdehyde of sandblasters [49.08 +/- 19.05micromole/l] was significantly higher than that of control population 1.92 +/- 0.33 micromole/l [p<0.001]. Urinary neopterin of sandblasters was 10.85 +/- 3.61 mmole/mole creatinine which was also significantly higher than control group 4.71 +/- 1.88 mmole/mole creatinine [p<0.001]. Correlation between occupational exposures of glass sandblasters to crystalline silica with blood serum malondialdehyde was significant [r2=0.279, p<0.01]. Malondialdehyde of blood serum and urinary neopterin could be regarded as biomarkers of exposure to crystalline silica aerosols
Résumé
The term "crystalline silica" refers to crystallized form of SiO2 and quartz, as the most abundant compound on earth crust, is capable of causing silicosis and lung cancer upon inhaling large doses in course of occupational exposure. In this study, airborne respirable dust samples were collected on mixed cellulose filters [25 mm diameter, 0.8 mm pore size], by using a cyclone separator at the flow rate of 2.2 l/min for a maximum volume of 800 liters. Infrared absorption spectrometry was used according to the "National Institute of Occupational Safety and Health" [NIOSH] method No. 7602 for analysis of samples. Risk assessment techniques predictive of silicosis and lung cancer were employed. The geometric mean of workers' exposure to crystalline silica in ten industrial fields [stone milling and cutting, foundry work, glass manufacturing, asphalt, construction, sand and gravel mining, sand blast, ceramics, bricks and cement manufacturing] was in the range of 0.132 to 0.343 mg/m[3]. Mortality rate of silicosis was predicted to be in range of 1 to 52 per one thousand exposed individuals. Risk of lung cancer mortality in exposed workers in the east zone of Tehran based on geometric mean exposure of industrial activity and 45 years of exposure was in range of 50 to 129 per one thousand. In terms of risk assessment of silicosis mortality, cumulative exposure of 21 percent of population complied with the notion of acceptable risk. In regard to lung cancer mortality, 100 percent of the population were expected to have an unacceptable risk after 45 years of active work experience. This study is the first of its kind in Iran demonstrating a profile of exposure in different groups of workers in the east zone of Tehran's greater city, covering 5.5 million populations. Considering the total population of one hundred thousand workers exposed to quartz in east zone of Tehran and aging of the current young workforce, numerous cases of silicosis and lung cancer are forecasted in near future