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 alert on Facebook from the Australian Animal Poisons Helpline, regarding dogs ingesting test buffer solutions that contain sodium azide, a preservative that is highly toxic. The organization said that the amount contained in individual tests is “very low” and “unlikely to pose a significant rxjmtzywisk” 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 29 antigen testing devices authorized 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. Health Canada did not immediately respond to questions regarding potentially harmful ingredients in RATs.
BinaxNOW and Panbio, 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. BD Veritor by Becton Dickinson and Co. and CovClear by Empowered Diagnostics also have 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 four 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, with CovClear explaining that aims to prevent azide build-up because the chemical may react with lead and copper plumbing that form highly explosive metal azides.
According to user documents posted on the U.S. Food and Drug Administration (FDA)’s website, the Ellume home test, Quickvue by Quidel Corp., and SD Biosensor Inc.’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.
InteliSwab 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 chemicals”, but that laboratory studies indicate they are non-toxic at the levels contained in its test.
Canadian instructions for CovClear and SD Biosensor Inc (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.
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The contents of a COVID-19 antigen rapid test kit are picture in Calgary, Alta., Tuesday, Jan. 4, 2022. THE CANADIAN PRESS/Jeff McIntosh
