On a mine site or a civil construction project, impairment isn’t a private matter — it’s a safety risk to everyone on the job. That’s why drug and alcohol screening has become a standard component of pre-employment medicals in safety-critical industries across Australia. But the landscape is shifting, particularly around medicinal cannabis, and WA employers in mining and civil construction need to understand where they stand.

Why screening is built into the recruitment process

In safety-sensitive sectors — mining, civil construction, transport, and warehousing — drug and alcohol screening at the pre-employment stage is routine. A worker who is impaired while operating heavy machinery, driving, or working at heights endangers not only themselves but their entire crew. Pre-employment screening confirms a candidate is fit to start work and reinforces a wider workplace culture where impairment is taken seriously.

Screening is typically conducted by urine or saliva sample, often with on-the-spot results during the same appointment, and laboratory confirmation conducted to the relevant Australian Standards (AS/NZS 4308 for urine and AS/NZS 4760 for oral fluid). Chain-of-custody procedures and an established, clearly communicated drug and alcohol policy are essential for the testing to hold up.

The medicinal cannabis complication

Here’s where it gets genuinely topical. The rapid growth in medicinal cannabis prescriptions has created real confusion for employers, because a positive cannabis result no longer automatically implies illicit use. So where does that leave a safety-critical workplace?

The position reflected in WorkSafe WA guidance is that safety obligations take precedence over the legality of substance use. Under the Work Health and Safety Act 2020 (WA), duty holders must manage risks to health and safety so far as is reasonably practicable, including risks arising from alcohol and drug use. This obligation applies regardless of whether a substance is prescribed, as prescribed and over‑the‑counter medicines may still impair a worker’s capacity to perform work safely.

In Western Australia, the WHS Act 2020 and the Work Health and Safety (Mines) Regulations 2022 govern workplace drug and alcohol obligations in mining, with specific requirements for mine operators to manage the risks associated with alcohol and drug use. [www4.austlii.edu.au]

Consistent with the broader WHS framework, the key principle is that employers must take reasonable steps to manage impairment risks, and a lawful prescription does not entitle a worker to perform safety‑critical work while impaired. For employers, the practical implication is that drug and alcohol policies need to address medicinal cannabis explicitly — covering disclosure, fitness-for-work assessment, and how prescribed substances are handled — rather than leaving it to be sorted out after a positive result.

Getting the policy and process right

Effective screening rests on more than the test itself. It needs a documented, role-relevant drug and alcohol policy that’s communicated to candidates up front; testing conducted to the correct Australian Standards under proper chain of custody; a fair and consistent process applied to all candidates for comparable roles; and a clear, lawful approach to prescribed medications and impairment. Done well, it’s defensible, respectful, and genuinely protective.

The takeaway

Drug and alcohol screening in pre-employment medicals is a core safety control for WA mining and civil construction — and the medicinal cannabis question has made getting the policy right more important, not less. The regulator’s message is straightforward: the duty to manage impairment comes first. Employers who pair proper screening with a clear, current policy are best placed to keep their sites safe and their obligations met.

To book a silica assessment online https://ohswa.com.au/booking/

*Sources: WorkSafe WA information sheet on medicinal cannabis and workplace safety (January 2025); WHS Act 2020 (WA) and WHS (Mines) Regulations 2022; Australian Standards AS/NZS 4308 and AS/NZS 4760; Australian occupational health industry guidance on pre-employment screening. This article is general information, not legal advice.*