The main effect of the 1999 regulations was to sort out a technical problem. Previous COSHH regulations needed frequent reissues to update the list of substances assigned maximum exposure limits ("MELs") - the list doubled from 30 to 60 substances over the last 10 years. In 1999 the list was removed from the COSHH regulations themselves and put into an annual Health & Safety Executive publication.

The 2002 COSHH regulations revoke (by reg 18) the 1999 regulations with effect from 21st November 2002 and then effectively re-enact them with modifications designed to ensure that they conform to current EC requirements (2002/11/01 - HSE Press Release re "New regulations will protect workers from dangerous substances" refers). The regulations impose duties on employers to protect employees and other persons who may be exposed to substances hazardous to health and also impose certain duties on employees concerning their own protection from such exposure, and prohibit the import into the United Kingdom of certain substances and articles from outside the European Economic Area.

The regulations have been subsequently amended by the Control of Substances Hazardous to Health (Amendment) Regulations 2003 SI 2003/978 made in March 2003 and by the Control of Substances Hazardous to Health (Amendment) Regulations 2004 SI 2004/3386 which came fully into effect on 6th April 2005. They provide amongst other things for a single system of "Workplace Exposure Limits" (WEL) to replace the previous two-tier system of "MELs" (maximum exposure limits) and "OESs" (Occupational Exposure Standards).

The HSE also runs a structured HSE CoSHH Essentials website - "Easy steps to control health risks from chemicals" with useful examples and publishes a useful Brief guide to the COSHH regulations.

For general notes see Health and Safety at work .