Drugs and alcohol are not dealt with by any specific health and safety law although, of course, drug and alcohol abuse affects people’s health, safety and welfare.
Under the Health and Safety at Work etc. Act 1974, employers have a duty to ensure the health, safety and welfare of their employees.
Misusing drugs and alcohol can put the user and other people at risk, and the Management of Health and Safety at Work Regulations 1999 state that employers must assess risk to their employees.
Of course, it is widely known that using controlled substances is illegal, whether at work or elsewhere. Specifically, it is an offence under the Misuse of Drugs Act 1971 for anyone to allow drugs to be used on their premises, which means that legal proceedings could be brought against an employer who knowingly allowed drugs to be used at work.
Where the worker with a drug or alcohol problem drives as part of their job, they could be committing an offence under the Road Traffic Act 1988 by being in charge of a vehicle when under the influence.
If somebody under the influence of drugs or alcohol works on a guided transport system such as a railway, they could be prosecuted under the Transport and Works Act 1992 for working whilst affected, and the employer could be liable for prosecution because it falls to them to ensure that their workers are fit to operate the system.