A leading drug researcher is warning against using the words 'synthetic cannabis' to describe the psychoactive substance that has killed seven people - and he says a regulated natural cannabis market could be worth investigating.

The surge in synthetic drug use is a global health risk, Chris Wilkins from Massey University warned on The AM Show, and it's dangerous to call the drugs synthetic cannabis.

"People then expect the effects to be like cannabis, but these are completely different compounds and are much more potent, and they have different effects than cannabis," he said.

The warning comes as health authorities confirm an eighth death from synthetic drug use in the last month. Counties Manukau DHB says a man in his mid-twenties was being treated for symptoms of synthetic drug use, but died overnight.

There has been some speculation the batch which has caused the deaths in Auckland contains household cleaning products. Acting Detective Inspector Peter Florence says samples sent away for analysis reveal the batch wasn't spiked with materials such as weed killer and fly spray.

Mr Wilkins said people are buying the drugs off the internet, and they enter the market in "clusters" or "waves".

Mr Wilkins said the drugs are produced in "semi-legal" operations in places like India and China.

"They are not regulated at all," he said. "Manufacture is ad hoc and it's sent here as synthetic cannabis."

Because they are new compounds, no research exists around them and people need to be extremely careful, he said.

But legislation and border policing could help prevent deaths from the use of psychoactive substances.

Mr Wilkins said regulation of psychoactive substances could "suck some of the demand out" and ensure a safer product. But it would never solve the problem.

He said a regulated market of natural cannabis could be worth experimenting with. A lot of people are buying psychoactive substances because they are cheaper than natural cannabis, but he said many users would prefer to be smoking marijuana.

"If you look at potency, it's safer," he said.

Through Peter Dunne's Psychoactive Substances Act, these psychoactive products are already illegal. They are not stockpiled drugs purchased before the Act removed substances off the shelves, but rather new and much more potent drugs.

Newshub.