A chemical commonly used to preserve food has been linked to a recent increase in suicide deaths in the UK, with young people and boys and men accounting for a disproportionately large share of cases. The findings come from a comprehensive analysis of available data from 2019-24 published in the open-access journal BMJ Public Health.
Researchers say the findings point to an urgent public health need to reconsider unrestricted access to the chemical in an effort to prevent further avoidable deaths.
Suicide death rates across the UK have generally declined since the early 1990s. More recently, however, there are signs that the numbers may be increasing. At the same time, reports from around the world have documented a growing number of suicides associated with sodium nitrite poisoning.
Researchers Examine Sodium Nitrite Poisoning Cases
To investigate whether sodium nitrite poisoning may be contributing to suicide deaths in the UK, researchers conducted a retrospective analysis of cases submitted to the country’s primary laboratory for postmortem testing of nitrite and its oxidized metabolite, nitrate.
The cases were submitted by coroners, forensic pathologists, and police forces between March 2019 and August 2024.
Over that period, the laboratory received 274 samples connected to 201 suspected cases of either deliberate or accidental poisoning across the UK, Ireland, and Gibraltar.
Most cases originated in Greater London, South East England, Ireland, and the Midlands. However, the researchers caution that this geographic pattern could reflect differences in coroner awareness and testing practices rather than the actual distribution of cases.
The number of cases increased substantially after 2019, which was the first year the laboratory began receiving samples for nitrite/nitrate assessment.
For the final analysis, researchers used only cases for which coroners had approved the use of the data. That represented 82% (164) of the cases received between 2019 and 2024.
Young People and Men Accounted for Most Cases
The average age among the cases was 28. Ages ranged from 14-74 for males and 17-82 for females.
Nearly three-quarters (71%) of all cases involved younger generations. Gen Z accounted for 33% (born 1981- 96), while Millennials accounted for 38% (born 1997- 2012, but listed up to 2005 to account for a separate category of minors, as 4% of cases were among those under the age of 18).
Men substantially outnumbered women overall, with (109) male cases compared with (52) female cases. Men made up more than half of cases in every generation except the oldest classified generation (Silent, born 1928-45), which included only one case, involving a woman.
Blood testing also revealed unusually high concentrations of nitrite and nitrate. In 87% of cases, levels were 100 times higher than would normally be expected physiologically. Researchers say this finding suggests that ingestion of the chemical was intentional.
True Number of Deaths May Be Higher
The researchers note several important limitations to the findings. Nitrite and nitrate testing is not routinely required in every suspected suicide, making it difficult to determine exactly how many deaths are associated with the chemical.
“It is therefore likely that the cases included here represent a substantial underestimate of the actual incidence. Secondly, the interval between death and sample receipt varied considerably, introducing the possibility that delays may have affected the accuracy of the biochemical measurements,” they say.
Despite those limitations, researchers say the increase in cases involving predominantly young people is particularly concerning because younger generations tend to have greater digital literacy.
“Intentional poisoning has contributed to these recent increases, and at least in the USA, this rise has been partly attributed to the use (and availability) of sodium nitrite,” they point out.
Researchers also highlighted the role that online information may be playing.
“This trend has emerged alongside freely accessible online information detailing how sodium nitrite can be obtained and used, disseminated both under the guise of providing mental health support and for more explicitly harmful purposes,” they explain.
Researchers Call for Urgent Action
The team says the findings support taking immediate steps to address access to sodium nitrite and the circulation of harmful information online.
“Collectively, these findings establish unequivocally that use of sodium nitrite in the UK as a method of suicide is both substantial and concerning,” they write.
The researchers also suggest that younger people’s greater familiarity with digital technology may make it easier for them to encounter harmful online material.
“Our data provide strong support for the suggestion that the improved digital literacy of younger people enables access to illicit online material promoting suicide practices and lends further support for calls for tighter legislation to prevent availability of such information in online forums,” they add.
Alongside efforts to restrict access and harmful information, the researchers suggest that emergency services could take additional steps to reduce the consequences of sodium nitrite poisoning. Providing an antidote (methylthioninium chloride kits) in ambulances, they say, would be “a simple and cost-effective, timely method to prevent the devastating consequences of ingestion.”
Lead researcher, Professor Amrita Ahluwalia, comments: “This is an extremely difficult subject to talk about, and we appreciate the impact that this might have on all those affected by suicide.
“What our research shows is deeply upsetting. But it makes clear why urgent steps are needed to regulate access to this chemical and to reduce the spread of harmful information about it online.”
