Kanala Chanvirat¹, Naesinee Chaiear^1,, Thitiworn Choosong²

Objective: Our aim was to determine the occupational exposure level for respirable crystalline silica (RCS) and respirable dust (RD) among sandstone workers. Materials and methods: This study was a descriptive analysis of the occupational exposure to respirable crystalline silica (RCS) and respirable dust (RD), utilizing personal air sampling from the breathing zone. The samples were collected throughout the 8-h working day: 88 samples were collected from workers performing stone cutting in mines and at home (wetting system), as well as stone chiseling and stone carving (22 samples each). Twenty-two samples were collected of the RD using the Gravimetric method (NIOSH 600), while for occupational exposure, the level of RCS was measured using a NIOSH7601 spectrophotometer. Results: Sand-stone workers had a geometric mean occupational exposure to RD of GM 1.84 mg/m³. The highest respiratory dust (RD) concentration (2.83 mg/m³) was found among the stone carvers. Those cutting stone at the mines had the next highest GM (2.65 mg/m³), while the lowest occupational exposure was seen among those chiseling stone(GM 0.9 mg/m3). The occupational exposure to RCS had a geometric mean of 0.10 mg/m³. The highest exposure group was for those cutting stone in the mines (GM = 0.14 mg/m³) followed by those carving stone (GM = 0.10 mg/m³). The moderate exposure group was for those chiseling stone (GM 0.05 mg/m³ ) followed by those cutting stone at home (GM = 0.03 mg/m³). The low exposure group had a GM of 0.03 mg/m³ for RCS. We found the quartz silica concentrations of the sandstone used in this area high (≤90%) as was the percentage of quartz silica in the airborne particulates for stone carving (≤71.4% by volume). Conclusion: The stone cutting in mines group and the stone carving group reached occupational exposure limits to RCS which exceeded the 0.05 mg/m³ OSHA PEL. It is essential to prevent such high exposure through engineering controls, by adapting tools and implementing medical surveillance. All groups had a RCS occupational exposure which would warrant medical surveillance as each group exceeded the OSHA action level of 0.0025 mg/m³.

silica, respirable crystalline silica, respirable dust, pneumoconiosis, sand stone