One term often mentioned by workplaces in regards to drug and alcohol testing is impairment.

What is important to realise is a positive drug and alcohol test, whether instant or laboratory, will in no way determine impairment. The results are also unable to determine when the drug or alcohol was last ingested, but does indicate there has been a recent use. It is important to remember the drug and alcohol policy does not focus on impairment.

Evidence between drug levels and impairment is sparse. On top of that, effects of drugs, including alcohol, vary from person-to-person.

Factors that may affect drug levels and impairment include:

  • Amount of drug consumed
  • Time over which drug was consumed (e.g. how many alcoholic drinks were consumed across a fixed time period)
  • Use of other drugs and medication
  • General mood
  • Body fat percentage and weight
  • General health
  • Tolerance to drugs and alcohol

To make the matter more complex, absence of drugs or alcohol does not mean there is no impairment. The simplest example of this is a hangover, where perception, behaviour and reflexes are altered – even if the person blows 0.000% blood alcohol concentration.

A word on impairment:

Impairment can be caused by a range of factors outside of the ingestion of alcohol and drugs. Factors that affect worker impairment can include fatigue, prescribed medications, pre-existing health conditions, heat, noise and work-related stress. It is less important to determine the cause of why a person is impaired, and more important to ensure the health and safety of the worker and those around them.

If a worker appears impaired, ensure they are out of harms way and that they do not pose a risk to others. Determining reason for impairment should occur after the worker is safe. Training for designated staff members to approach possibly impaired workers is an important strategy to have within a workplace. This training should include effective approach methods and should inform staff members of the possible signs of impairment. Making accusations of possible causes for impairment of the worker should be avoided.

  1. Commission for Occupational Safety and Health: Guidance Note: Alcohol and other drugs at the workplace 2008
  2. Safe Work Australia: Work Related Alcohol and Drug Use: A Fit For Work Issue 2007
Dr Keith Adam
M.B., B.S., Fellow ACOM, Fellow AFOEM, RACPChief Medical Officer

Dr Keith Adam is a Senior Specialist Occupational Physician with Sonic HealthPlus and an Associate Professor of Occupational Medicine with the University of Queensland. Treating and rehabilitating injured workers since 1984, Dr Adam has extensive experience in determining what duties injured workers may be able to perform, and managing return to work programmes.

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