COSHH legislation is a systematic approach to the control of risk presented by substances in the workplace. It is defined under the Health and Safety at Work Act 1974. Important information regarding the control of hazardous substances is found in the Control of Substances Hazardous to Health Regulations 1999 and 2002 and 2020. New or revised workplace exposure limits for 13 substances have been introduced from 17 January 2020. This latest version of EH40/2005 workplace exposure limits has been updated to include the new and revised workplace exposure limits (WELs) as introduced by the Carcinogens and Mutagens Directive (EU) 2017/2398 amending Directive (2004/37/EC). This new version will guide those responsible for controlling exposure to hazardous substances at work. Important note: The WELs listed in EH40/2005 workplace exposure limits supersede any WELs contained in other HSE guidance or publications.