In the second of a two-part article, Gordon Tranter now examines the legal information related to drug and alcohol testing at work. He will also outline some of the issues involved in creating a drug and alcohol policy.

Employers have a general duty under the Health and Safety at Work etc Act 1974 (HSWA) to ensure, as far as is reasonably practicable, the health, safety and welfare of employees. If an employer knowingly allows an employee under the influence of drugs or excess alcohol to continue working, and this places the employee or others at risk, they could be prosecuted. Similarly, the HSWA requires employees to take reasonable care of themselves and others who could be affected by what they do.

The Misuse of Drugs Act 1971 covers nearly all drugs with misuse and/or dependence liability. The Act makes the production, supply and possession of these controlled drugs unlawful except in certain specified circumstances. If an employer knowingly permits the production or supply of any controlled drugs, the smoking of cannabis or certain other activities to take place on their premises they could be committing an offence.

The law on testing for alcohol and drugs at work

Drug and alcohol testing are highly controversial and raise issues of privacy and human rights. Employees cannot be forced to take drug and/or alcohol tests unless it is a condition of their employment and is set out in their contract of employment, or the employee has given their consent. Obtaining samples without consent could constitute the criminal offences of assault or battery. Employers who carry out unnecessary tests could be open to legal challenge, particularly under the Human Rights Act 1998, which includes the right to respect for private and family life and home.

Testing in safety critical industries

Provisions included in health and safety legislation, together with transport legislation, may lead employers in safety-critical industries to drug test. Drug and alcohol testing is carried out on employees carrying out jobs in which impairment due to drugs or alcohol could have disastrous effects for the individual, colleagues, members of the public and the environment, eg drivers, pilots and some machinery operators.

The Transport and Works Act 1992 makes it a criminal offence for certain workers to be unfit through drink and/or drugs while working on railways, tramways and other guided transport systems. The operators of the transport system would also be guilty of an offence unless they had shown all due diligence in trying to prevent such an offence being committed. The Road Traffic Act 1988 states that any person who, when driving or attempting to drive a motor vehicle on a road or other public place or when in charge of a motor vehicle on a road or other public place, is unfit to drive through drink or drugs is guilty of an offence.

Random testing

Drug testing should only be introduced following proper consultation with staff and their representatives and should be even-handed. HSE recommends in INDG 240 that for alcohol screening “in addition to changes to the contract of employment, you should obtain the written consent of the individual for each test”. The employer needs to demonstrate that testing for drugs and/or alcohol is necessary to combat a risk(s) and is limited to those employees that need to be tested to deal with the risk. The employer must obtain informed consent from the employee before carrying out a drug test.

An employer could be liable to prosecution under the Equality Act 2010 for targeting drug testing at a particular group or for implementing drug testing in a discriminatory way. Selection for testing must be genuinely random.

Data protection of drug and alcohol testing results

Information about an employee's health, which includes the results of alcohol and drug testing, is sensitive personal data. Employers must, therefore, ensure they adhere to the Information Commissioner's Code of Practice when carrying out drug or alcohol testing to avoid breaching the Data Protection Act 1998. The results of a drug test must remain confidential, even if the test is failed.


If an employee fails a drug test, their employer may be able to dismiss them summarily for gross misconduct, particularly if they work in a safety-critical profession and their drug use has noticeably impacted their job performance. However, the employer must always ensure that they follow the statutory disciplinary procedures, together with any of their own policies and procedures, before taking a decision to dismiss. Failure to follow the statutory procedures will result in the dismissal being automatically unfair.

The case for/against drug and alcohol testing

Although the evidence for a link between drug use and accidents at work is not conclusive, it is clear that drug- and alcohol-induced intoxication is a source of risk in the workplace. Workplace testing for alcohol and drugs is appealing. It can provide speedy on-site results, although positive results have to be confirmed by a laboratory if action against the donor is intended.

The use of alcohol and drugs testing to address the risks from alcohol and drug consumption in the workplace is contentious. It is complex, with scientific, ethical, economic, legal and social dimensions.

No consensus on effectiveness

It is accepted that drugs do impair cognition, perception and motor skills and consequently are likely to have adverse consequences in the workplace. However, at present there is no consensus on whether there is a link between drug use and accidents at work, or whether testing has a significant deterrent effect on drug and alcohol consumption or that it reduces accident rates. However, proving the existence of a deterrent effect is difficult, if not impossible.

There is little or no conclusive evidence on the effectiveness or otherwise of drug and alcohol testing as a means of enhancing performance. Even if testing has beneficial effects upon performance, there can be adverse effects including the impact on staff morale and workplace relationships and the cost of excluding illicit drug users from jobs that they may be well-qualified to perform.

Other criticisms

Drug testing is not a measure of current intoxication or impairment and the test is unable to determine:

  • when the drug was consumed and consequently how much was consumed

  • the level of impairment experienced as a result of consumption.

Different drugs are detectable in urine for different lengths of time, dependent upon factors such as age, height, sex, weight, purity of drug, the dose and how often the drug is used. Consequently, the test can reveal information about drug use that have no impact on safety, productivity or performance. For some drugs a person may still test positive after taking a drug days, weeks or months before.

Cheating the urine test

There are numerous strategies used by cheats for passing the urine drug or alcohol test, which is the most commonly used method of testing. This can be achieved by substitution, dilution or the addition of adulterants including so called “masking agents” sold commercially.

The use of adulterants can cause false negative results in drug tests by either interfering with the screening test and/or destroying the drugs present in the urine. Dilution may be employed in an attempt to dilute the concentration of drugs in the sample. Clinically, the accepted method to test for adulteration or dilution is to determine certain urinary characteristics such as creatinine, pH and specific gravity and to detect the presence of glutaraldehyde, nitrite and oxidants pyridinium chlorochromate (PCC) in urine.

Some cheaters simply give clean urine samples that are not theirs, especially if the drug test is not being supervised. The clean sample can be from a “clean” urine donor or from powdered urine, which can be bought or self-made.


Companies that are concerned about alcohol or drugs in the workplace should have a drugs and alcohol policy which contain a clear outline of the aims and purposes of the policy and set out the rules and procedures around alcohol and/or drug use. The policy on testing should:

  • outline who is covered by the policy and whether a particular group (eg, employees carrying out safety-critical work) is subject to tighter restrictions

  • outline what constitutes misuse

  • outline the testing procedure and why the test is necessary

  • outline what happens if a test proves positive and the disciplinary action that may be taken.

The policy should be developed in consultation with staff and union representatives.


Alcohol and drug testing is widely used in safety-critical and other occupations where the public is entitled to expect the highest standards of safety and probity. In addition to their purpose of preventing accidents, these tests have the added advantage of maintaining public confidence.

Testing must take account of legal considerations and be either a contractual requirement or carried out with the employees’ consent. The testing should be limited to the employees that need to be tested to deal with the risk and should not be discriminatory. Random tests should be genuinely random.

If such testing is to be used it should not be implemented as a stand-alone approach. It should be incorporated as part of a comprehensive program for workplace alcohol and drug-related harm.

Last reviewed 28 February 2012