TORONTO -- Self-testing COVID-19 rapid antigen tests authorized by Health Canada for purchase and use by the general public contain very low quantities of ingredients that are potentially harmful in larger amounts.
Concern is highlighted in an from the Australian Animal Poisons Helpline, regarding dogs ingesting test buffer solutions that contain sodium azide, a preservative that can be highly toxic, according to the U.S. Centers for Disease Control and Prevention (CDC). The Australian helpline said that the amount contained in individual tests is “very low†and “unlikely to pose a significant risk†in the majority of cases.
"The actual risk of poisoning in any individual case will depend on the amount of sodium azide ingested and the weight of the animal involved," the Facebook alert said.
"Very small animals, or those animals that ingest a number of vials of buffer solution could possibly be at risk of poisoning."
Other antigen tests contain ProClin 300, a different preservative that also comes with safety warnings.
There are by Health Canada as of Jan 24, 2022, the majority of which are categorized for lab-based or point-of-care use. Eight of the 10 devices approved under self-testing are antigen tests. The federal agency defines self-testing devices as those that can be purchased and used by the general public.
Online documentation for the products contained warnings about the ingredients, but Canadian versions of the user instructions found for some of the tests did not list sodium azide or ProClin 300.
WHAT IS SODIUM AZIDE?
Sodium azide is a “rapidly acting, potentially deadly chemical†that exists as an odorless white solid, , which lists the substance under Chemical Emergencies. Exposure to small amounts could cause symptoms within minutes, including dizziness, headache, nausea and vomiting, rapid breathing and heart rate, the CDC says. It does not specify what constitutes a small amount. Larger amounts can cause additional symptoms such as convulsions, loss of consciousness, or even respiratory failure.
In Canada, sodium azide currently of a “toxic substance†under of the Canadian Environmental Protection Act, 1999, because they do not enter the “environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health.â€
Health Canada and Environment and Climate Change Canada regularly reviews new information that could change the level of exposure to a substance and would take regulatory action as necessary, according to a spokesperson for the agency.
Andre Gagnon also told CTVNews.ca in an email that Health Canada reviews the ingredients and components in a test kit during its scientific evaluation process and that instructions for use of the diagnostic devices should list the quantity, proportion or concentration of each reactive ingredient.
“The toxicity of any substances depends on dose and exposure. At this point, there is no evidence that the use of the substances in these buffer liquids present a hazard, as long they are being used as instructed in these test kits,†Gagnon said, adding that users should only handle the components of the kits as instructed by the manufacturer or with guidance from public health authorities.
“Health Canada is currently reviewing the labelling of all rapid tests authorized to date to make sure that appropriate warnings are included in the instructions for use, and will take appropriate action as necessary.â€
WHAT DO THE TEST KITS SAY?
and , the COVID-19 antigen self-tests made by Abbott, both contain sodium azide, according to documentation posted online by the company that contain warnings about the chemical. by Becton Dickinson and Co. also has warnings about sodium azide. BinaxNOW says it contains 0.0125 per cent of the chemical, while Panbio and BD Veritor says it has less than 0.1 per cent.
All have varying levels of warnings in user documents found online that say sodium azide is a harmful chemical that can be toxic if inhaled, swallowed, or exposed to skin. If the solution comes in contact with the skin or eye, instructions advise users to flush with “copious amounts†of water. If disposing in a sink, some direct users to flush with a large volume of water.
According to user documents posted on the U.S. Food and Drug Administration (FDA)’s website, the home test, by Quidel Corp., and .’s self test, which are also authorized by Health Canada, contain ProClin 300.
Warnings vary from mild skin and eye irritation to stronger advisories. Quickvue, which says it contains 0.03 per cent concentration of the ProClin 300, and Ellume note that the ingredient is harmful if swallowed or inhaled and causes severe skin burns and eye damage, while Ellume also notes that it is very toxic to aquatic life and carries long-lasting effects.
by Orasure Technologies says in a document posted on the FDA site that its solution contains Triton X-100 and Proclin 950, which are “potentially harmful chemicalsâ€, but that laboratory studies indicate they are non-toxic at the levels contained in its test.
Canadian instructions for and (distributed by Roche Canada) does not list any potentially hazardous ingredients, but CovClear tells users to flush with copious amounts of water if the chase buffer solution comes in contact with the skin or eye. SD biosensor does not contain any warnings or precautions regarding the solution.
A spokesperson for SickKids Hospital in Toronto told CTVNews.ca that the Ontario Poison Centre (OPC) has received approximately 55 calls “related to misuse of or accidental access to rapid antigen tests since September 1, 2021†involving people, not animals. However, the spokesperson notes that the number of calls may not be representative of the total amount of exposures since the calls to the OPC are voluntary and it’s possible that “other substances were also involved in these calls.â€
Ontario Poison Centre can be reached at 1-800-268-9017
For other provinces and regions
Correction:
This story has been corrected to remove a reference to the CovClear test containing sodium azide. The company behind the test says: "As of the time of our authorization in Canada, CovClear and its components do not contain sodium azide."
