Underestimation of respirable crystalline silica (RCS) compliance status among the granite crusher operators in Malaysian quarries

Abstract

The aim of this study is to determine exposure levels as well as compliance status on respirable dust and respirable crystalline silica (RCS)-quartz exposure among crusher operators at Malaysian quarries. The exposure level at each crushing process was compared. Monitoring was performed among 70 crusher operators at nine quarries. Eight hours long-term personal samples were collected according to the National Institute of Occupational Safety and Health (NIOSH) Manual Analytical Method (NMAM) 0600 for respirable dust and NMAM 7500 for respirable crystalline silica (RCS-quartz). A questionnaire on silica dust monitoring and control was also sent to all granite quarries in Malaysia. The results indicated that the mean percentage of RCS-quartz in silica dust was 23.7 %. The mean value for crusher operators’ exposure was 0.426 mg m−3 for respirable dust and 0.091 mg m−3 for RCS-quartz. Around 30.5 % of crusher operators were exposed to RCS-quartz levels above the permissible exposure limit (PEL) based on Malaysian’s Occupational Safety and Health Regulations 2000. Operators in charge of combined secondary and tertiary crusher plants were exposed to 0.116 mg m−3 of RCS-quartz, which was higher compared to those operating individual plants. Results on posted questionnaire indicate that Malaysian quarries are more preferred to perform respirable dust monitoring (37 %) instead of specific RCS-quartz monitoring (22.6 %). Low exposure to respirable dust may conceal the need to justify comprehensive crystalline silica dust monitoring and lead to underestimation of RCS-quartz exposure. A high percentage of non-compliance exposure on personal RCS-quartz exposure should establish the need for quarry management to focus on better implementation of dust control systems.