The North Staffordshire Medical Institute supports research in a wide range of fields – including substance misuse. We spoke to expert Dr Roger Bloor about his study of cannabis vaporisers.


If you believed the manufacturers, you might think that vaporisers were a safe way of using cannabis.

The smoke-free inhalers are sold as a harmless way of getting high without lighting up. They do allow users to avoid some of the cancer-causing chemicals in cannabis smoke – but it comes at a price, according to research funded by the NSMI. The vaporiser fumes do not contain as much tar, hydrogen cyanide and nitrous oxide as would be produced by a cannabis ‘joint’. But they do contain toxic levels of ammonia, putting users at risk of serious lung disorders.

Lead researcher Roger Bloor, a former psychiatrist and addiction specialist, explains: “Cannabis, which is illegal in this country, is very widely used but carries risks from things like tar, which clogs up your lungs and can cause all sorts of health problems.

“Some people devised a way of using cannabis without smoking it by heating it up on an electronic plate and that reduces the risk. We investigated and we found that it does reduce the tar, but there’s a massive spike in the production of ammonia when you use these devices. The type of level whereby if you were running a factory, it would be shut down as a public health risk.”

Ammonia, which is commonly used in agriculture as fertiliser, is a poisonous chemical that can cause blindness, lung damage or death when inhaled at high concentration. Large quantities were detected in cannabis vapour produced in the labs at Keele University and analysed with cutting edge SIFT-MS
technology. The study looked at popular vaporiser brands available online, including the notorious Blue Meanie and Volcano models.

“We used standardised cannabis, where we knew what was in it, and we also had a license to have any seized drugs sent to us so we had street cannabis as well,” says Dr Bloor. “Street cannabis contains far more ammonia than the farmed cannabis usually used for research. This is because ammonia is found in the buds of the plant, which street cannabis is full of, rather than the leaves.”

The original research, funded by a grant of just £4,869 in 2004, went on to inspire several follow-up studies and an article in world-renowned journal Addiction. It is regularly cited as a warning to those considering buying a vaporiser as a ‘safe’ alternative to cannabis cigarettes. The devices, which cost from £35 to £350, are still widely available from specialist shops.

Dr Bloor said: “People recommend them, and they recommend things like water pipes, to take out the high tars. There’s a whole industry producing things to technically reduce the risk from cannabis which people are keen to use, but the research into them is not complete.”

Even if the devices could make smoking cannabis physically safe, they would not prevent the risk of psychiatric side effects. “The major risk of cannabis is that it can trigger schizophrenia,” he adds. “The strong stuff can be highly dangerous, but with the lower-powered stuff most people use the main risks are physical.”

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