May 12, 2023

Forensic pathologists play vital role in recognizing trends in sodium nitrite poisoning

Programs: Postgraduate, Research: Hematopathology, Impactful research, Alumni
a spoonful of salt
By Jenni Bozec
Tyler Hickey
Dr. Tyler Hickey

“Cases like this show how local forensic pathology units are the first line of defense in recognizing and raising awareness of harmful new trends that can affect people’s lives,” says Dr. Tyler Hickey when discussing the recent high profile sodium nitrite poisonings.

Earlier this month, the media reported that several deaths by suicide in the UK, Canada and US had been linked to sodium nitrite sold on a website run by Kenneth Law, through a business listed at a Mississauga post office box.

In early 2019, the Provincial Forensic Pathology Unit (PFPU) in Toronto encountered multiple cases of deaths resulting from potential sodium nitrate and sodium nitrite poisoning which caught the attention of Dr. Hickey, Assistant Professor in the Department of Laboratory Medicine and Pathobiology in the Temerty Faculty of Medicine, and a forensic pathologist with the PFPU.

Sodium nitrate and sodium nitrite are potentially toxic salts, similar in appearance to table salt, and are readily available compounds used in food preservation and other commercial applications. Ingesting too much, which could only be a few tablespoons, causes a reaction in the hemoglobin of the blood converting it to a form, called methemoglobin, that is unable to properly carry oxygen. This causes a condition called Methemoglobinemia (MetHb) where the body is essentially starved of oxygen from the inside. A healthy body should have less than 1% methemoglobin; the first reported case of sodium nitrite poisoning in New Zealand in 2010 had an ante-mortem methemoglobin concentration of 82.6%.

Hickey had noticed these deaths and how challenging they were to diagnose. There are no obvious signs in the organs, but the skin can show a purple colouring - hard to detect in those with darker skin pigmentation. “There is a blood test that can be done to confirm the diagnosis, but it is not a routinely ordered test.  So, unless there are other obvious signs from the scene, such as remnants of the salts, or a specific suicide note left by the deceased, cases could be missed,” he explains.

Hickey undertook a case review, investigating all the potential sodium nitrate/nitrite deaths in the Province. The resulting paper, published with fellow LMP faculty member, Dr. Michael Pickup, explains that he identified a total of 28 MetHb deaths over the 20-year analysis period, with 82% of the deaths occurring in 2019 and 2020. 

“We have determined that ingestion of sodium nitrite/nitrate as a method of suicide is an increasing trend in our province. The reasons for this cannot be definitively explained; and research on this topic can be challenging,” he explains in the paper.

Being the first death investigation office in Canada to recognize the worrying trend, Hickey completed the study to raise awareness of the issue and give other death investigators, coroners, and pathologists information on how the cases could be missed, and details of what to look out for to aid diagnosis.

“It is a vital part of our work as we are often the first to see what is causing novel deaths. When we spot something new or unusual, or notice new patterns or trends, we have a duty to research and investigate that so we can spread awareness and knowledge. I see our roles as forensic pathologists as a very valuable asset and important part of public health protection,” states Hickey.