At the end of 2019, the coronavirus began spreading around the world, infecting humans and causing pneumonia known as COVID-19. The number of infections increased rapidly and in some places, healthcare systems were overrun. In an attempt to contain the spread, many countries limited transportation and closed down schools, colleges, universities and nonessential businesses. The negative impacts of the novel coronavirus pandemic are widespread and significant. However, one of the unintended consequences of the efforts to contain the spread of the disease was reduced air pollution. Many air pollutants are molecules produced from the combustion of fuels. NASA monitoring instruments measured decreased concentrations of NO2 and CO2 which resulted in a positive health benefit. (1,2)
According to the US EPA and WHO, long-term exposure to ambient air pollution increases mortality and morbidity from cardiovascular and respiratory disease and lung cancer and decreases life expectancy. (3) The two pollutants responsible for most of the disease burden are fine particulate matter (PM2.5) and ground level ozone (O3).
In response to poor air quality in the United States, the government established the Clean Air Act (CAA) in 1970. The law was amended in 1977 and again in 1990. This comprehensive federal law regulates air emissions from stationary sources such as factories, refineries and power plants and mobile sources such as cars, trucks and buses. CAA also authorizes the Environmental Protection Agency (EPA) to establish National Ambient Air Quality Standards (NAAQS). The goal of these standards is to protect the health and welfare of the public and regulate the emissions of hazardous air pollutants. Hazardous air pollutants are known to cause cancer and other serious health impacts. The NAAQS have been set for six common pollutants, known as the criteria air pollutants. These include ground level ozone, particulate matter carbon monoxide, lead, sulfur dioxide, and nitrogen dioxide. Four of the six criteria pollutants exist as gaseous molecules in the atmosphere. The EPA publishes the standards on their website.
These six common pollutants are not the only substances that we need to worry about in the air. Soot from fires is problematic and even hazardous pollutants from industry are in our air. An example of this was ethylene oxide was being emitted from sterilization factories in Lake County IL in 2017. Ethylene oxide is cancer causing and people in the surrounding area were inhaling it. The Illinois EPA intervened and both companies were required to reduce their emissions to protest the public health. For more information visit the Lake County Health Department. Air pollution is problematic when we breathe in these compounds, they can cause all sorts of health problems from cancer, cardiovascular diseases to asthma. You can find out more here: https://www.cdc.gov/air/pollutants.htm.
The EPA has also established the U.S. Air Quality Index (AQI) as a simple method for reporting air quality to the general public. Lead is the only criteria air pollutant not included in the AQI. The AQI ranges from 0-500. The lower the value the better the air quality. Additionally, the AQI is divided into six color-coded categories. Green (0-50) represents good air quality that poses little to no risk even to sensitive groups. Red (151-200) is considered unhealthy and some members of the public may experience health effects. Values above 300 are considered hazardous with everyone more likely to be affected. (4)
The emission of hazardous air pollutants is not limited to human-made sources nor are people only exposed outside. Natural sources include volcanic eruptions and forest fires which are of increasing concern due their greater frequency and duration. Building materials and cleaning solvents are two fairly common sources of indoor pollutants.
(1) NASA Earth Observatory. Airborne Nitrogen Dioxide Plummets Over China https://earthobservatory.nasa.gov/images/146362/airborne-nitrogen-dioxide-plummets-over-china (accessed 19 July 2020)
(2) Evans, S. Analysis: Coronavirus set to cause largest ever annual fall to CO2 emissions. https://www.carbonbrief.org/analysis-coronavirus-set-to-cause-largest-ever-annual-fall-in-co2-emissions (accessed 19 July 2020).
(3) Cohen, Aaron J et al. “Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015.” Lancet (London, England) vol. 389,10082 (2017): 1907-1918. doi:10.1016/S0140-6736(17)30505-6.
(4) AQI basics. https://www.airnow.gov/aqi/aqi-basics/ (last accessed 19 July 2020).