Will worker DNELs derived under the European REACH regulation extend the landscape of occupational exposure guidance values?

Derived no-effect levels for workers (wDNELs) under the European REACH legislation have many aspects in common with occupational exposure limits (OELs). In an attempt to examine under which circumstances wDNELs might be used as exposure guidance outside their intended application, we compared derivation methods, coverage of substances and numerical values of wDNELs against two regulatory OEL lists (European Commission and Sweden) and three sets of recommendations (European SCOEL, German MAK and US ACGIH). Finally, we looked closer at wDNELs where SCOEL concluded that data were insufficient to derive an OEL. Major differences between wDNELs and OELs include regulatory background, intended use, actors involved, substance selection criteria, transparency and procedure of derivation, and operationalisation in terms of risk management measures. As of summer 2018, approximately five times more substances were covered by wDNELs than by the five sets of OELs examined herein. Meanwhile, many occupationally relevant pollutants were not covered by wDNELs, e.g. one-third of Swedish OELs lack corresponding wDNELs. We also note that wDNELs and OELs for the same substance may vary considerably, up to several orders of magnitude. In conclusion, with extensive substance coverage, wDNELs extend the landscape beyond the OELs. That said, important limitations are (1) that many air pollutants relevant for workers' health are not covered by REACH, and (2) concerns for inconsistencies in the derivation of wDNELs and in their level of protection. In particular, that route-to-route extrapolation is a common practice that may be grossly misleading when the effect of concern is local, e.g. sensitisation.