Sodium nitrite, a chemical commonly used to preserve food, has been linked to a rise in suspected suicide deaths in the UK. Young people, boys and men made up a disproportionately high share of the cases, according to a comprehensive analysis of data published between 2019 and 2024 in the open-access journal BMJ Public Health.
The researchers say the findings highlight an urgent public health need to review unrestricted access to sodium nitrite and reduce the risk of further preventable deaths.
Suicide rates across the UK generally declined from the early 1990s onward. However, recent data suggest that this trend may be changing. At the same time, reports of suicide involving sodium nitrite poisoning have increased in the UK and other countries.
Study examines sodium nitrite poisoning in the UK
To assess whether sodium nitrite poisoning could be contributing to suicide deaths, researchers conducted a retrospective analysis of cases submitted to the UK’s leading laboratory for post-mortem testing of nitrite and its oxidised metabolite, nitrate.
The samples were submitted by coroners, forensic pathologists and police forces between March 2019 and August 2024.
During this period, the laboratory received 274 samples linked to 201 suspected cases of intentional or accidental poisoning across the UK, Ireland and Gibraltar.
Most cases were recorded in Greater London, south-east England, Ireland and the Midlands. However, the researchers cautioned that this pattern may reflect differences in coroner awareness and testing procedures rather than the true geographical distribution of cases.
The number of suspected cases rose significantly after 2019, the first year in which laboratories began receiving samples for nitrite and nitrate analysis.
For the final analysis, the researchers included only cases for which coroners had approved the use of the data. This represented 82% of the cases received between 2019 and 2024, or 164 cases.
Young people and men accounted for most cases
The average age of those involved was 28. Males ranged in age from 14 to 74, while females ranged from 17 to 82.
Almost three-quarters (71%) of the cases involved younger people. The researchers reported that 33% involved Generation Z and 38% involved millennials, although 4% of cases involved people under 18 and were classified separately as minors.
Men significantly outnumbered women, with 109 male cases compared with 52 female cases. Men accounted for more than half of the cases in every age group except the oldest generation, although only one case in that group involved a woman.
Blood tests also showed unusually high nitrite and nitrate concentrations. In 87% of cases, levels were more than 100 times higher than normal physiological levels. The researchers said this pattern was consistent with intentional ingestion.
The true number of deaths may be higher
The researchers acknowledged several limitations. Nitrite and nitrate testing is not routinely conducted in every suspected suicide case, making it difficult to establish the precise number of deaths linked to sodium nitrite poisoning.
“Thus, the cases included here are likely to significantly underestimate the true incidence,” the researchers wrote. “Second, the interval between death and sample receipt varied widely, and the delay may have affected the accuracy of the biochemical measurements.”
Despite these limitations, the researchers said the rise in cases involving younger people was particularly concerning. Younger generations may be more likely to encounter harmful online content because of their greater familiarity with digital technology.
“Intentional poisoning has contributed to the recent increase, and at least in the United States, some of this increase is attributable to the use and availability of sodium nitrite,” the researchers noted.
The study also examined the possible influence of online information.
“This trend has emerged with freely accessible online information detailing how to obtain and use sodium nitrite, disseminated either in the name of providing mental health support or for more explicitly harmful purposes,” the researchers explained.
Researchers call for urgent action
The researchers say immediate action is needed to address access to sodium nitrite and the spread of harmful information online.
“Taken together, these findings clearly demonstrate that the use of sodium nitrite as a suicide method in the UK is substantial and alarming,” they wrote.
They also said that young people’s digital literacy may increase their exposure to online content that promotes suicidal behaviour.
“Our data provide strong support for the suggestion that increased digital literacy among young people allows them to access illegal online content that promotes suicidal behaviour, and further supports calls for stronger legislation to prevent such information from being made available in online forums,” they added.
Alongside measures to restrict access and remove harmful online information, the researchers suggested that emergency services could take further steps to reduce the effects of sodium nitrite poisoning. They said carrying an appropriate antidote, such as a methylthioninium chloride kit, in ambulances could offer a “simple, cost-effective and timely way to prevent the devastating consequences of ingestion.”
Professor Amrita Ahluwalia, the lead researcher, said: “This is a very difficult subject to talk about and we deeply understand the impact this has on everyone affected by suicide.”
“What our research shows is deeply upsetting, but it also highlights why urgent action is needed to regulate access to this chemical and reduce the spread of harmful information about it online.”
Source: www.sciencedaily.com