Bleach Emissions Interact Substantially with Surgical and KN95 Mask Surfaces.

Area of Science:

• Environmental Chemistry
• Public Health
• Chemical Engineering

Background:

• Masks and bleach disinfectants were widely used during the COVID-19 pandemic.
• Bleach disinfection generates hazardous chemical species like hypochlorous acid (HOCl), chlorine (Cl2), and chloramines.

Purpose of the Study:

• To investigate the chemical interactions between masks and bleach disinfection.
• To quantify the generation and persistence of toxic species after mask disinfection.

Main Methods:

• Experiments were conducted in a ventilated chamber with a manikin and breathing system, wearing surgical or KN95 masks.
• Chemical concentrations were measured using chemical ionization mass spectrometry (CIMS) and Vocus proton transfer reaction mass spectrometry (Vocus PTRMS).
• Mass transfer modeling was employed to understand chemical behavior on and around the mask.

Main Results:

• HOCl, Cl2, and chloramines were detected during disinfection, with concentrations 2-20 times higher in the chamber than behind the mask.
• Masks acted as a sink during disinfection but became a source of chemical exposure for over 4 hours post-disinfection.
• Humidification increased chloramine formation, linked to ammonia and HOCl uptake.

Conclusions:

• Masks can act as a persistent source of chemical exposure following bleach cleaning events.
• Understanding these chemical dynamics is crucial for assessing the safety of disinfected masks.