A petition is calling for the World Health Organization to act quickly to establish indoor air quality guidelines to reduce the spread of airborne diseases such as coronavirus.
The petition which urges explicit guidelines around air humidity in public buildings is being supported by members of the medical and scientific community.
Headed by Infection Control Consultant at Harvard Medical School, ASHRAE distinguished lecturer & member of the ASHRAE Epidemic Task Group, Dr Stephanie Taylor, the petition asks the Director General of WHO to:
- Review the scientific evidence related to indoor humidity and respiratory immune system response, viral transmission and virus inactivation, and;
- Produce guidelines on the minimum lower limit of indoor humidity in public buildings
Scientific evidence shows that indoor air maintained between 40-60% relative humidity (RH) has significant benefits for human health. This is the optimal level for the human respiratory immune system and will reduce the spread of respiratory disease.
According to the Centers for Disease Control and Prevention (CDC), it is thought that the COVID-19 virus can spread “through respiratory droplets produced when an infected person coughs, sneezes or talks.” According to a news release from the National Institutes of Health on March 17, these respiratory droplets seem to be detectable in the air for as long as three hours.
“Humidification of indoor air gives people a simple means of actively combatting seasonal respiratory infections.”
With regard to Covid-19 behavior in the 40-60% RH band, the airborne droplets containing the virus retain moisture and so become heavier and fall out of the air, allowing physiochemical reactions to deactivate the virus. However when RH is lower than 40% airborne droplets containing the virus shrink through evaporation making them lighter. This enables particles to float for longer in the air, increasing the likelihood of infection. The vast majority of respiratory virus suspended in dry atmospheres also survive longer and remain infectious for far longer than those floating in air with 40-60% RH.
Dr Walter Hugentobler, MD, general physician, former lecturer Inst. of primary care at the University of Zürich, added: “Raising air humidity by humidification reduces the risk of virus spread in hospitals and other buildings at low-cost and without causing negative effects.
“It can also be easily implemented in public buildings, both in private and workplace environments with relative ease. Humidification gives people a simple means of actively combatting seasonal respiratory infections.”
The scientists argue that published guidance on minimum humidity would result in:
- Significant reduction of infections from respiratory diseases
- Thousands of lives being saved due to this reduction
- Alleviation of the burden on Global healthcare services due to seasonal respiratory disease
- World economies benefitting from less absenteeism
- Improved indoor environment and health for millions of people
The WHO currently has guidance on indoor air quality issues like pollutants and mold but no recommendations for minimum humidity
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