128 Assessing potential health risks from multi-exposure to chemicals in U.S. workplaces: findings from the OSHA database

Introduction The combined effects of occupational exposure to multiple chemicals on health can be substantial. However, the most prevalent multi-exposure situations and their toxic effects remain understudied. We assessed the health risks from multi-exposure to chemicals in U.S. workplaces using the Occupational Safety and Health Administration’s (OSHA) measurement database. Methods We analysed personal air measurements for the period 1971-2021 summarized by workplace situation (WS), corresponding to measurements taken for the same job title, within a company, within a year. We calculated hazard quotients (HQ) by dividing the agents’ concentrations by their ACGIH® threshold limit value. We calculated the mixtures’ hazard indices (HI) by summing the HQs of agents by combination of WS and toxicological class (n=24) using the MiXie tool, which identifies classes of toxic effects for >700 chemicals. Results We extracted 609,233 measurements of 206 chemicals from 162,473 WSs. Workers in 58,252 WSs were exposed to ≥2 agents, of which 21,563 had an HI>1, indicating overexposure for at least one toxicological class. Toxicological classes with the highest HIs among multi-exposed WSs were lower airway damage (median 0.41; interquartile interval 0.05-1.9; percentage of overexposed WSs 35%), ototoxicity (0.28; 0.04-1.1; 26%) and central nervous system (CNS) damage (0.26; 0.02-1.2; 28%). For these three classes respectively, the most frequent multi-exposures leading to high values of HI were manganese-iron oxides, toluene-xylene and manganese-lead. Conclusions Although the OSHA database does not necessarily represent a random sample of U.S. workplaces, our approach provides insights into the health risks of occupational exposures to prevalent chemical mixtures.