The surgical N95 mask has been held up as the gold standard when it comes to protecting against Covid.

But a study quietly re-shared by the National Institutes of Health in spring suggests the tight-fitting mask may expose users to dangerous levels of toxic chemicals.

Researchers from Jeonbuk National University in South Korea looked at two types of disposable medical-grade masks, as well as several reusable cotton masks.

The study found that the chemicals released by these masks had eight times the recommended safety limit of toxic volatile organic compounds (TVOCs).