Major drug dealers on the dark web have begun to voluntarily ban the synthetic opioid fentanyl, deeming it "too dangerous" to trade, according to The Guardian.

Those trading on the digital black-market have been "delisting" the supercharged painkiller blamed for an estimated 30,000 drug overdose deaths in 2017 - classifying it along with fully automatic firearms and explosives that are considered too high risk to trade.

Fentanyl is up to 100 times stronger than heroin.

"If they’ve got people selling very high-risk commodities then it’s going to increase the risk to them," said Vince O'Brien of the UK's National Crime Agency (NCA). "There are marketplaces that will not accept listings for weapons and explosives – those are the ones that will not accept listings for fentanyl. Clearly, law enforcement would prioritise the supply of weapons, explosives and fentanyl over, for example, class C drugs – and that might well be why they do this."

O'Brien added: "There are also drug users on the dark web who say on forums that they don’t think it’s right that people are selling fentanyl because it is dangerous and kills a lot of people."

One type of fentanyl, carfentanyl, is thousands of times stronger than heroin and O’Brien confirmed that police had made a number of small seizures of the substance in the UK. In the US, fentanyl has taken a significantly more profound hold on the drugs sector and has replaced heroin in many major US drug markets, precipitating a more deadly phase of the nation’s opioid epidemic. The number of overdose deaths associated with fentanyl and similar drugs has grown to more than 29,000 a year, from 3,000 five years ago. Deaths were up by more than 45% in 2017. -The Guardian

According to O'Brien, the NCA is working with US law enforcement agencies to try and stave off a similar fentanyl epidemic.

"We are working closely with international partners in terms of how the threat developed there. It’s an emerging new drug, a threat we’re taken very seriously because of what happened in the US," added O’Brien. "Every time we take down a dark web vendor we follow up with customers, and when we have done that, a number are turning up dead – there’s a real cautionary tale there."

The NCA has scored several victories against UK fentanyl dealers - which typically acquire the drug from China before selling sell it on the dark web.

The first fentanyl case to be sentenced in the UK involved Kyle Enos, 25, from Newport who was jailed for eight years in February. Enos had procured the narcotic from China, selling it worldwide and to customers in 30 UK police areas. -The Guardian

NCA investigating officer Colin Williams said "We realized within a number of hours we had to deal with this very quickly." When they tracked down approximately 160 customers of Enos's, they found that four of them were already dead. "We can’t say whether they took the drug but they were certainly on his [customer] list," said Williams.

Last year the largest underground fentanyl marketplace, Alphabay, was shut down following a global police investigation. After several more have met similar fates, it appears that the deadly opioid is simply too hot to handle.