Recommended Exposure Limit (REL) 1 : A National Institute for Occupational Safety and Health (NIOSH) time-weighted average (TWA) concentrations for up to a l0-hour workday during a 40-hour workweek
Department of Health and Human Services (US federal public health agency), The Agency for Toxic Substances and Disease Registry (ATSDR), Glossary (Total Petroleum Hydrocarons), GA, USA 1999. http://www.atsdr.cdc.gov/toxprofiles/tp123-c9.pdf, (Globally Harmonized Sys of Class and Labl of Chem - Brit) {635}