A study published in April found disposable masks can have toxic chemicals

Experts said this could make newly instated mask mandates ineffective

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.