Nitrous oxide has been used as pain relief and as a sedative for more than 150 years - and in more recent times, as a recreational drug.

Misuse of the gas has become an escalating problem across New Zealand.

Last week, a crisis meeting was held in Hawke’s Bay to address growing concern over the levels of abuse. At least two people have reported to Hawke’s Bay Hospital’s emergency department with nerve injuries from chronic nitrous oxide use.

It is illegal to sell the canisters - known as nangs - to under 18s or for recreational use, but because they are also used to whip cream, they’re sold legally online and in dairies around New Zealand.

The penalty for selling nitrous for personal use is imprisonment for up to two years for an individual; for a company, it’s a fine of up to $500,000. Anyone found with an “unapproved psychoactive substance” can be fined up to $500.

However, use remains rife, particularly among younger people, and parents of habitual users are raising alarm bells over long-term effects.

So, what is the impact of nangs on a user’s health, and should we be more worried about it?

The brain

The canisters provide an immediate – but short-lived – high when the gas is inhaled.

Dr Neil Anderson, a neurologist at Auckland Hospital and the Neurological Foundation medical adviser, says a major problem is with the “huge doses” being used.

“People buy hundreds of these nangs and use them over 24-48 hours, or you can buy canisters of nitrous oxide and fill a balloon and use it that way,” he tells the Herald.

Emily Hughes, the principal science adviser at the NZ Drug Foundation, says the availability of bigger canisters has led to increased problems.

“Large canisters make it easier for a person to use larger amounts and make it harder to keep track of how much has been used,” she tells the Herald.

If people don’t take regular or long enough breaks when inhaling nitrous, they can be deprived of oxygen which can lead to unconsciousness and possible brain damage.

Nitrous oxide canisters gathered for disposal in Hawke's Bay. Photo / Doug Laing.

Regular or long-term use can cause vitamin B12 deficiency, as nitrous oxidises the cobalt ion in vitamin B12, rendering it inactive. This can cause nerve damage and can lead to permanent neurological disorders.

“It affects the spinal cord principally, so people lose their sense of position in their legs, [get] numbness in their legs,” Anderson explains.

“Because you lose your position sense, it affects your balance. It affects the nerves in your legs and arms, so it’s not just the spinal cord... B12 is important through your whole body, through the whole nervous system.

“The particularly severe [cases] can develop weakness in bladder control and it also affects the brain, so it affects people’s behaviour and thinking.”

Frequent nitrous use can also cause brain fog and memory loss.

The body

One major risk with nitrous oxide use is that it can lead to injuries or accidents.

“Nitrous oxide can make a person feel relaxed, euphoric and giggly and can cause a sense of dissociation or a dreamlike state,” explains Hughes.

“[It] can also make a person feel disoriented, dizzy/light-headed and unco-ordinated.”

“This includes falls or trips from standing up too quickly during or after use,” Hughes says.

It can also affect someone’s ability to drive, slowing reaction times and impairing judgment, which can lead to serious accidents on the road.

In January this year, Bay of Plenty police reported a “concerning increase” of nitrous oxide use while driving.

Other physical injuries can happen when the gas is inhaled directly from canisters.

“ [This] can cause freeze burns and in rare cases, lung rupture due to the pressure in the canister,” warns Hughes.

“If exposed to large volumes of nitrous oxide without proper intake of oxygen, nitrous oxide use can cause diffusion hypoxia, which is where the body is not getting sufficient air. While rare, this can be very dangerous.”

Can side-effects be reversed?

According to Anderson, most negative effects usually disappear over time.

“The people we see have been just sort of apathetic and lethargic, and that usually comes right,” he says.

However, if the spinal cord is affected, this can be more serious. While the damage is usually short-lived, in severe cases, users may be disabled for weeks or months.

“They do improve if they stop using and get B12 replacement,” says Anderson, “but there’s a risk that they don’t make a complete recovery”.

Inhaling smaller amounts and taking regular breaks can help lessen the risk of B12 deficiency, says Hughes.

“It is also important to know the signs and symptoms of vitamin B12 deficiency and to see a doctor as soon as possible.

“As with all drugs, ensuring that appropriate harm reduction information is available can help keep people safer.”

You can find more information and advice on The Level, run by the New Zealand Drug Foundation.

Bethany Reitsma is a lifestyle writer who has been with the NZ Herald since 2019. She specialises in all things health and wellbeing and is passionate about telling Kiwis’ real-life stories.