Another reason why wearing a mask is a foolish and dangerous notion. Masks rapidly reduce the body’s oxygen levels (hypoxemia) which compromises your immune system; this has multiple, adverse effects and is especially detrimental to those with pre-existing conditions including asthma and other respiratory illnesses. The elderly and immunocompromised* individuals (see below) are at greatest risk.
*Examples of persons with weakened immune systems include those with HIV/AIDS; cancer and transplant patients who are taking certain immunosuppressive drugs; and those with inherited diseases that affect the immune system (e.g., congenital agammaglobulinemia, congenital IgA deficiency). The risk of developing severe disease may differ depending on each person’s degree of immune suppression.
“Oxygen deficiency. An oxygen deficient atmosphere has an oxygen content below 19.5% by volume. Oxygen deficiency may occur in confined spaces, which include, but are not limited to, storage tanks, process vessels, towers, drums, tank cars, bins, sewers, septic tanks, underground utility tunnels, manholes, and pits.”
SOURCE – Occupational Safety and Health Administration (OSHA) Technical manual, Section VIII: Chapter 2, III. General Information, B. Airborne (or Respiratory) Hazards, 7. Oxygen deficiency.