The California Division of Occupational Safety and Health’s (Cal/OSHA) Health Effects Advisory Committee (HEAC) for the Development of Permissible Exposure Limits (PEL) will meet on June 4, 2019. According to the meeting agenda, HEAC will discuss the selection of Priority 1 substances for HEAC review. HEAC has posted a draft 2019 Priority 1 List consisting of ten chemical substances. The draft List includes titanium dioxide, ultrafine (<100 nanometers (nm)). According to HEAC, the eight-hour threshold limit value is 0.3 milligrams per cubic meter (mg/m3). Although California has adopted PELs for a number of airborne contaminants, for titanium dioxide, Table AC-1 in Section 5155 of Title 8 of the California Code of Regulations refers to particulates not otherwise regulated. The respirable fraction for particulates not otherwise regulated is 5.0 mg/m3. The draft Priority 1 List includes a factor for each substance that is the key consideration used for the ranking. Titanium dioxide, ultrafine (<100 nm) is listed with a factor of 2, “[a] substantial change in the value of an [occupational exposure limit (OEL)] that could contribute to increased protection of workers if adhered to by employers.”