The United National Transport Union has cautioned those who use cannabis privately to remember their companies' drug use and random testing policies.

This comes after three of its members were fired and then lost their case at the CCMA. 

"This means that irrespective of the fact that the Constitutional Court ruled that you are entitled to smoke cannabis in the privacy of your home, you cannot expect your employer to deviate from implementing the zero-tolerance rule," UNTU said on Friday.

The three union members had failed random drug tests at work and, because they work with heavy machinery, their companies have a "zero tolerance" policy regarding drug testing. Most of the union's members work at Transnet and the Passenger Rail Agency of SA - companies which have "zero-tolerance" policy on drugs or alcohol.

The workers' defence was that they had smoked cannabis at home, and not during working hours. 

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UNTU general secretary Steve Harris said Commission for Conciliation Mediation and Arbitration commissioner Charles Oaks had found that the employer had communicated the zero-tolerance and random testing policy to employees at the time of employment, and that they agreed to the policy when they took the jobs.

Oakes found that the prohibition of the employer was reasonable, as they work with dangerous heavy machinery.

The employer is also responsible, in terms of the Occupational Health and Safety Act, to prevent accidents in the workplace. 

"Yes, you can smoke cannabis at home or use it for medical purposes, but if the employer wants to test you at any stage, and you test positive, you can be dismissed," said Harris.

The Constitutional Court ruled last year that it was unconstitutional to prevent private cannabis use, but a legal process still has to be gone through to rework laws and regulations in line with this ruling. Many recreational and medicinal users, as well as cannabis entrepreneurs, are currently finding their own ways of dealing with the grey areas in the law until the law is rewritten.

Grey area

Eugene Du Plessis, of the company SA Mobile Drug Testing, told News24 that random drug and alcohol testing were only allowed if it is written into a work contract and signed by the employee. It is compulsory for many occupations, especially those where heavy machinery is involved. 

He said there was a grey area over whether the policy also covers people using cannabis by-products for health reasons, but the tests can also detect levels of opioids and amphetamines.

He cautioned that THC levels build up gradually in the body, the longer a person uses cannabis. 

THC - or Tetrahydrocannabinol - is the compound in cannabis that gets people "high".

The THC will be gone within a few days for a person using it for the first time. 

However, the daily or weekend user's test will show higher levels of THC and could go over the current limit of 50ng/ml in urine that companies will accept.

When can companies test you

According to Du Plessis, these are the most common jobs where people are required to sign a document agreeing to submit to random drug and alcohol testing:

- Train drivers;

- Pilots;

- Ship's captains;

- Drilling companies;

- Deep sea divers who do underwater maintenance and repairs;

- Anybody on an oil tanker or an oil rig;

- Some fields of medical practice;

- The engineering and heavy machinery professions;

- CEOs and top executives, particularly in the financial sector, or employees who provide high-level financial advice;

- Some call centres;

- Some infrastructure maintenance companies that do repairs such as replacing a municipal utility line.

And, a recent trend is random drug testing at schools. This can only be done with parental consent.