Why IAQ Matters
Research has shown that air quality and COVID-19 together with other viruses and communicable diseases are correlated. A big point of concern when talking about IAQ is that indoor air is usually 2 to 5 times more polluted than outdoor air and most persons spend the majority of their time indoors. An adult person breathes about 22,000 times a day consuming more than 30 pounds of air molecules per day.
Various factors affect indoor air quality, which are affected by the indoor space and a person’s habits and it is important to take these into consideration.
Key IAQ Factors- Ideal Ranges
Group A: Virus Promoting Factors
Temperature- 66 to 75 F:
According to research by Casanova Lisa, et al., published in the American Society of Microbiology, the infectious rate of viruses is significantly reduced at moderate room temperatures compared to colder temperatures < 39 F. At warmer temperatrures > 86 F, transmission of the virus is blocked or becomes highly inefficient.
Relative Humidity – 40 – 60%
In an environment with RH% lower than 40%, droplets from a cough or sneeze lose their moisture quickly resulting in droplets becoming “dry aerosols” and capable of staying in the air for longer time periods creating a viral cloud that remains infectious for much loner time periods. Virus particles are most inactive at 50% humidity and retain their infectiveness the further from that median average, plateauing at 20% and 80%. 50% RH is the most ideal in terms of fast virus inactivation.
PM 2.5 – 15 ug/m3 (micrograms per cubic meter)
Particle Matter also known as “particle pollution” is a complex mixture of extremely small particles and liquid droplets. PM at 2.5 microns in size or smaller will be inhaled deeply into the lungs and can cause irritation and corrosion of the alveolar wall which impairs lung function. They are also known to carry microbiomes, a microbe that stay alive and protects us against germs and diseases, as well as aids in digestion of foods.
A study conducted by Feng, Cindy et al published in the Journal of Environmental Health showed an increase in vulnerability to influenza-type illnesses when levels of PM2.5 were above the ideal range. The study suggests that these PM2.5 stay airborne longer, creating a “condensation nuclei” which virus droplets attach to. This becomes part of the viral cloud that gets inhaled by people increasing the risk of infection.
Common sources of PM 2.5 are smoking, candles, cooking, space heaters, furnaces, poorly maintained HVAC systems and poorly ventilated fireplaces.
Carbon Dioxide Co2 – < 800 ppm
Co2 has long been used as an indicator of good indoor air quality primarily because of its association with ventilation. When Carbon dioxide levels are high, it may indicate that your spaces are not well ventilated or there is an untypical source present for the production of this gas.
Chronic inflammation caused by persistent high Co2 levels is not ideal for our health, moreover longer exposure to high Co2 can cause fatigue, headaches, and dizziness. It is also possible to develop hypercapnia acidosis, characterized by increased levels of carbon dioxide in the blood that will suppress the human immune system and make on more susceptible to disease. Some typical causes of Co2 indoors are heavy population of people, improperly ventilated spaces, improperly maintained combustion devices and exposure to high output of car and diesel fuel burning exhaust.
Nitrogen Dioxide- NO2- below 53 ppb
High levels of Nitrogen Dioxide indoors is a result of outdoor NO2 entering your indoor air environment as well as combustion sources inside the space. A study by the Environmental Research Journal, short -term exposure can irritate airways while long-term exposure can lead to chronic illness and respiratory infections with viruses. Asthmatics may also experience longer symptomatic periods and increased need for medication for children.
Examples of sources of NO2 are automobiles from an attached garage and busy urban streets, appliance with defective installations, gas stoves, kerosene heaters, chimneys etc.
Total Volatile Organic Compounds (TVOC)- OSHA PEL of .75ppm and an action level of 0.5 ppm. Levels between 0.3 to 0.5 mg/m3 are considered acceptable.
According to the US EPA VOC’s are emitted gases from certain solids or liquids. VOC’s include a variety of chemicals, some of which may have short and long term adverse health effects. They can also react with other chemicals in the air and become more dangerous to human health. Exposure to VOCS over a 24-hour period can irritate the lungs causing nausea and making it difficult to breath. Long term exposure to harmful VOC’s over months can affect the liver, kidneys, and central nervous system.
Group B: Infectious Disease Promoting Factors
Airborne Mold Spores- No set standard. Guidelines are less than outside, no pathogenic species and total spore levels , <1000 spores per cubic meter with no presence of pathogenic mold types.
Not all persons are susceptible to mold spores at the same exposure levels. However even allergenic mold types can cause hay fever and asthma reactions as well as sinusitis, pneumonia and endocarditis.
Airborne Mold and Bacteria Bioaerosols – no total quantitative exposure standa;ds, based primarily upon exposure to mycotoxins and endotoxins.
Bioaerosols are very small airborne particles ranging from 0.001 to 100 um (micrometer) that originate biologically from plants and animals and can contain living or organisms. Therefore, pathogenic and or non- pathogenic dead and alive microorganisms may exist in bioaerosols. Bioaerosols are easily shifted from one environment to another because of their small and light weight. ln recent years, exposure to bioaerosols in both occupational and residential environment has drawn much attention in light of their probable impacts on human health.
How Does COVID-19 Spread?
How Air Pollution and IAQ affect mortality Rates
Long before COVID-19 arrived, air pollution and poor indoor air quality have been linked to higher rates of illness and mortality. SARS Coronavirus research has found evidence that the virus is frequently spread in the air.
Ke Lan, an expert virologist from Wuhan University, hypothesized that these tiny airborne droplets can cause coronavirus infections. Scientists from the Department of Community and family medicine in Hong Kong found evidence supporting this also. According to Harvard University, the same trend holds true. Their study looked at the data from years 2000 to 2016 and found that long term exposure to airborne particulate matter results in an increase in COVID-19 death rates, based upon their updated data of April 24,2020 suggesting that even an increase of 1 ug/m3 of 2.5 PM can increase the likelihood of mortality by 11%.
1. Casanova Lisa, et al. “Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces.” Applied and Environmental Microbiology, American Society for Microbiology, 2010, https://aem.asm.orqlcontent/76/9/2712.
2. Lowen, Anice and John Steel. “Roles of Humidity and Temperature in Shaping lnfluenza Seasonality.” Journal of Virology, American Society for Microbiology, 2014, https:/jvi.asm.orq/content/88/14/7692.
3. Yu-Fei, Xing, et al. “The impact of PM2.5 on the human respiratory system.” Journal of Thoracic Disease, 8 Jan. 2016, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC47401251.
4. Qin, Nan, et al. “Longitudinal survey of microbiome associated with particulate matter in a megacity.” Genome Biology, 3 Mar. 2020, https://genomebiology.biomedcentral.com/articles/10.1186/s13059-020-019640x.
5. Feng, Cindy, et al. “lmpact of ambient fine particulate matter (PM2.5) exposure on the risk of influenza-like-illness: a time-series analysis in Beijing, China.” Environmental Health, 11 Feb.2016, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC47503571.
6. Jacobson, Tyler, et al. “Direct human health risks of increased atmospheric carbon dioxide.” Nature Sustainability, 8 Jul. 2019, https://www.nature.com/articles/s41893-019-0323-1.
7. Becker, Susanne and Joleen Soukup. “Effect of Nitrogen Dioxide on Respiratory Viral lnfection in Airway Epithelial Cells.” Environmental Research, Science Direct, Aug 1999, https://www.sciencedirect.com/science/article/abs/pii/So013935199939634.
8. “People Who Are at Higher Risk for Severe lllness.” Centers for Disease Control and Prevention, 14 May 2020, https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-at-higher-risk.html.
9. Wu MS, Xiao, et al. “COVID-19 PM2.5.” Harvard University, 24 Apr. 2020, https://proiects.iq.harvard.edu/covid-pm.
10. Martelletti, Luigi and Paolo Martelletti. “Air Pollution and the Novel Covid-19 Disease: a Putative Disease Risk Factor.” Nature Public Health Emergency Collection, PMC, 15 Apr. 2020, https://www.ncbi.nlm.nih.qov/pmc/articles/PMC7156797/#CR6.
11. Setti, Leonardo, et al. “The Potential role of Particulate Matter in the Spreading of COVID-19 in Northern Italy: First Evidence-based Research Hypotheses.” medRxiv, Cold Spring Harbor Laboratory, 17 Apr 2020. https://www.medrxiv.org/content/10.1101/2020.04.11.20061713v1.article-info.
12. Su, W, Wu, X., Geng, X. et al. The short-term effects of air pollutants on influenza-like illness in Jinan, China. BMC Public Health 19, 1319 (2019). https://doi.orq/10.1186/s12889-019-7607-2.
13. Lewis, Dyani. “ls the coronavirus airborne? Experts can’t agree.” Nature, 2 Apr. 2020, https://www.nature.com/articles/d41586-020-00974-w.
14. Yu, lgnatius, et al.’Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus.” The New England Journal of Medicine, 22 Apr- 2004,
15. “Getting your workplace ready for COVID-19.” World Health Organization, 3 Mar. 2020,
16. “Blijft het coronavirus op voorwerpen in leven? En zo ia, hoe lang?” RTLNieuws, 24 Mar 20, https://www.rtlnieuws.nl/neiuws/nederland/artikel/5043611/coronavirus-covid-19-ziekte-virus-zorgen-vragen-besmettelijk.