Exposure-response relationships for platinum salt sensitization in precious metal refinery workers: a 16-yr retrospective study

Abstract

BACKGROUND: Occupational allergy to soluble chlorinated platinum (Pt) salts, also known as chloroplatinates, poses a serious health problem in precious metal refineries. We aimed to assess the exposure-response relationship between soluble Pt salts exposure and Pt salt sensitization (PSS) in a 16-yr retrospective cohort study (2000 to 2015). METHODS: We analyzed routinely collected data from 5 Pt refineries. In total, 1,614 newly hired workers who entered the industry since 2000 regularly underwent skin prick tests. Exposure to soluble Pt salts was modeled using 2,982 personal air samples. The relationship between time-varying exposure levels and PSS development was analyzed by Cox proportional hazards regression, adjusting for smoking, atopy, and facility. RESULTS: PSS was diagnosed in 117 workers (1.48 per 100 person-years of follow-up time) with median time to PSS of 1.9 yr, and with an estimated median exposure level of 53 ng/m3 (P5-P95: 8 to 302 ng/m3) at the time of PSS development. Statistically significant quantitative exposure-response relationships between PSS and cumulative and current exposure were found. Exposure-response curves showed a steep increase in PSS incidence at exposure levels up to 100 ng/m3, with no or only a slight further increase at higher levels. CONCLUSIONS: We found a clear exposure-response relationship between soluble Pt salts exposure and PSS incidence among newly hired workers. Despite the limitations inherent to the retrospective study design, this cohort study contributes to the growing body of evidence that the widely adopted occupational exposure limit of 2,000 ng/m3 does not adequately prevent PSS and should be reevaluated.