THE discarded silver gas cartridges have become a regular sight at Dixon Park and Bar Beach car parks, and now medical experts are calling for tighter restrictions on the sale of "nangs" following a rise in presentations to Australian emergency departments.
Experts from the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney want more regulation around the sale of nitrous oxide gas cartridges - colloquially known as nangs - due to the risk of "potentially serious" harm when used recreationally.
Nitrous oxide - or laughing gas - is used by dentists and medical professionals for sedation and pain relief.
It is also a food additive, used to aerate whipped cream, and sold in gas cartridges online and in convenience stores.
According to NDARC, an increasing number of Australians are also using nitrous oxide recreationally - inhaling the gas to produce a fleeting feeling of euphoria and excitement.
An Ecstasy and Related Drugs Reporting System (EDRS) survey found nitrous oxide use jumped among people who regularly use ecstasy and/or other illicit stimulants.
From 2003 to 2015, about a quarter of those surveyed had reported using nitrous oxide in the past six months.
The proportion doubled to 50 per cent in 2018.
"It's always tricky to say why a particular drug might be increasing in use or popularity. But it potentially could be related to perceptions of safety," Dr Rachel Sutherland, NDARC's deputy program lead of drug trends, said.
"It's also quite easily available - you can purchase it very easily at convenience stores or online. And it's pretty cheap."
A recent study of 60 emergency departments across NSW found presentations related to nitrous oxide use increased from fewer than 10 in 2012 to more than 60 in 2018.
The Australian Institute of Health and Welfare (AIHW) reported in their National Drug Strategy Household Survey that the use of inhalants, which included nitrous oxide, increased from 0.4 per cent of participants in 2001, to 1.7 per cent in 2019.
According to Professor Shane Darke from NDARC, recreational nitrous oxide use has the potential for harmful effects in the short and longer term.
"If you're in a medical situation and you're being given nitrous oxide ... it's mixed with oxygen. These people aren't doing that. What they're doing is covering their faces and inhaling pure gas," he said.
"Now the problem with that is there's no oxygen.
"You run the risk of asphyxia."
He said that while using nitrous oxide, people were also at risk of entering a delirious state.
"They can be a risk to themselves and others," he said.
NDARC said emergency physicians had also started noticing people presenting with jerking and odd movements - signs of nerve damage - after using nitrous oxide.
"[Nitrous oxide] interferes with the absorption of Vitamin B12. This leads to neurological damage and eventually in severe cases, spinal degeneration," Professor Darke said.
"In an acute case you might be able to reverse that with infusions of B12. But in chronic cases it's irreversible."
NDARC said it was important to note people with neurological symptoms had been "heavy users" of nitrous oxide - inhaling the gas every day for months and consuming hundreds of canisters at a time.
They said more research is needed to understand the effects of light to moderate use.
On October 1, 2022, the Therapeutic Goods Administration (TGA) implemented the reclassification of nitrous oxide as a Schedule 6 poison, which means product labels must contain warnings and safety directions.
Some states, such as South Australia and Western Australia, have introduced restrictions on purchasing nitrous oxide, such as age limits.
"With any kind of regulatory intervention, it's really important that it's accompanied by harm reduction and education campaigns," Dr Sutherland said.
"We don't know if people who are using nitrous oxide, particularly at a high level or frequency, are aware of the associated neurological risks.
"Raising awareness of these risks and encouraging people to seek help early if they experience symptoms, such as persistent tingling and numbness, after nitrous oxide use is critical."
