Occupational Exposure to Rock Wool and Glass Wool and Risk of Cancers of the Lung and the Head and Neck: A Systematic Review and Meta-Analysis

Objective: To conduct a review and meta-analysis of risks of cancers of the lung and head and neck (HN) from exposure to rock wool (RW) and glass wool (GW). Methods: We performed a systematic review and meta-analysis of risk estimates of lung and HN cancer in epidemiologic studies of workers exposed to man-made vitreous fibers (MMVF), specifically RW and GW. Results: Sixteen estimates of lung cancer risk yielded a summary relative risk (RR) of 1.21 (95% CI = 1.11 to 1.32, based on 1662 exposed cases). Corresponding RRs were 1.26 (95% CI = 1.10 to 1.44) in studies of production workers (with similar risk for RW and GW workers), 1.06 (95% CI = 0.77 to 1.48) in studies of end users, and 1.18 (95% CI = 0.98 to 1.42) in community-based studies. The summary RR for HN cancer was 1.36 (95% CI = 1.13 to 1.63, 414 exposed cases). With a few exceptions, all studies that assessed the risk of lung or HN cancer according to various indices of MMVF exposure failed to detect a dose-risk relation. There was limited evidence of a confounding effect of tobacco smoking. No clear excess of pleural mesothelioma has been reported in MMVF-exposed workers. Conclusions: Despite a small elevation in RR for lung cancer among MMVF production workers, the lack of excess risk among end users, the absence of any dose-risk relation, the likelihood of detection bias, and the potential for residual confounding by smoking and asbestos exposure argue against a carcinogenic effect of MMVF, RW, or GW at this time. Similar conclusions apply to HN cancer risk among workers exposed to MMVF.