By: Benjamin Brown-Steiner, Archana Dayalu, Jennifer Hegarty, Karen Cady-Pereira, Thomas Nehrkorn, Matthew Alvarado
From sky-darkening smoke billowing from raging wildfires to the invisible but indelible imprint of greenhouse gas accumulation in the atmosphere, the reality and potential dangers of human emissions into our atmosphere have been almost impossible to ignore. Indeed, in its various forms, air pollution is responsible for millions of deaths a year and causes severe, if localized, economic damage.
As we continue to learn about the impact of our emissions on our atmosphere, our planet, and our health, companies and industries may be held liable for the health and climate effects that air pollution cause, thus necessitating changes in their activities. It’s a complicated subject, made more so by the disparate impacts and time scales on which human emissions operate.
The short and long-term risks of emissions
Many forms of human behavior generate emissions that are released into our atmosphere, from the simple act of breathing to the burning of fossil fuels for transportation and energy to manufacturing and agricultural processes. Together, these compound to release different emissions that could lead to various impacts on our atmosphere, environment, and selves.
These human-made (or anthropogenic) emissions can have short- or long-term impacts on atmospheric composition depending on the chemical species they contain, and thus have impacts of corresponding duration on human health and safety.
Short-term impacts arise mostly from chemical species that remain in our atmosphere for days to weeks. These species affect local and regional air quality, and include nitrogen oxides, sulfur dioxide, ammonia, carbon monoxide, volatile organic compounds, and aerosols. The creation of ozone, which is not emitted directly but triggered via chemical reactions from nitrogen oxides and organic compounds, also has substantial implications for human health.
Long-term impacts arise from chemical species that linger in the atmosphere for decades to centuries, including greenhouse gases such as carbon dioxide and methane. These gases can alter the global climate and, in turn, affect local weather and air quality.
The health risks of human emissions
Perhaps the most tangible health risk that arises from anthropogenic emissions comes in the form of air quality-related phenomena, such as smog and haze events. While there are also natural sources of acute pollutants, such as smoke plumes from forest fires or dust storms, human activities can exacerbate these natural sources’ severity and frequency. These emissions can affect human cardiovascular, cerebrovascular, and respiratory health, and contribute to heart disease, stroke, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections.1 2 Every year, these emissions cause roughly 7 million premature deaths worldwide, with the majority (4.2 million) arising from ambient air pollution.
The chemical species that are emitted from these events remain in the atmosphere anywhere from hours to weeks and thus tend to produce regional effects. For instance, smoke plumes that result from increasingly severe forest fires regularly affect air quality in the western United States, but are rare in the East. Similarly, emissions that result from the burning of fossil fuels (gas, diesel, natural gas, coal) are concentrated in regions of high population densities, such as cities, or near transportation corridors. The number of chemical species that influence air quality are in the tens of thousands, and while our ability to observe, model, and understand their sources, atmospheric interactions, and impacts on human health has been improving for decades, there is still much to learn.
A less tangible but very threatening consequence of human emissions on health and safety comes from the much more durable greenhouse gases and the resultant impact on global climate and local weather. Under a warming climate, heat waves and forest fires may become more frequent and more severe, as can droughts and tropical storms. Many other components of our ecosystems could be altered, including snowfall, growing season length, animal migration patterns, and spring leaf buddings. These impacts can be long-lasting and, due to the integration of these emissions in our transportation and energy systems, difficult to avoid.
Many chemical species that are of concern for air quality impacts are co-emitted by the same sources that emit chemicals that affect the global climate, and thus systematic changes that reduce one type tend to reduce the other. For instance, if an air quality program was implemented to shift from gasoline and diesel fuel vehicles to renewable energy electric vehicles, there would be an improvement in the air quality near roads and a reduction in overall greenhouse gas emissions. As a result, this program would effectively reduce the threat of both health and climate risks.
Four air quality issues to keep on your radar
Biomass burning and forest fires
Smoke from wildfires and crop residue burning can lead to periods of extremely poor air quality, even in countries where other air pollution emissions are tightly regulated. This smoke harms public health directly through increases in cardiovascular and respiratory disease, as well as mortality. Additionally, the smoke can reduce visibility, thus impairing traffic safety.
Poor air quality from smoke can lead to school closures3 and depress economic activities such as tourism. While most sources of air pollution in the United States over the past few decades have decreased, the frequency of wildfires and the smoke they emit are increasing in many regions as our climate changes, thus providing another source of pollution that can harm public health.
Fossil fuel extraction and use
The well-established, long-term risk of fossil fuel use correlates to high emissions of climate-changing greenhouse gases, but significant air pollution is also emitted throughout the cycle of fossil fuel processing, including aerosols, nitrogen dioxide, and ozone. Coal exemplifies the fossil fuel air pollution chain; from extraction4 to transportation—via diesel-powered heavy-duty trucks—to emissions, the health and death toll is severe. Coal use in the United States is responsible for 7,500 to 52,000 air pollution-related deaths annually.5 Fossil fuel combustion overall creates air pollution that kills an estimated 3 million to 4 million people a year worldwide.6
Consider this: As of December 1, 2020, the coronavirus pandemic has claimed more than 1 million lives globally. If we were to treat air pollution as a virus, we would be facing multiple pandemics every year. Poor air quality also reduces our capacity for resilience in the face of disasters. For instance, an increase of even 1 microgram per cubic meter (mg/m3) of fine particulate matter pollution (PM2.5) is associated with a corresponding 8 percent increase in the coronavirus death rate in the United States.7 For reference, the U.S. national PM2.5 standard is 12 mg/m3.
Indoor air quality in our homes
If poor air quality is a silent killer,8 9 then at our peril we ignore the indoor air quality in our homes, which is unregulated and generally missing in our understanding of what it means to stay healthy. We don’t usually think about what’s collecting in the less-ventilated, smaller-volume space that is our indoor environment. Given that the average American spends 90 percent of their time indoors (and this was pre-COVID-19),10 poor indoor air quality can be dangerous. Many of the causes are, in theory, preventable. In particular, an increasing body of research shows that gas stove ranges are one of the biggest contributors to poor indoor air in the United States.11 12 The use of gas stoves can result in levels of such pollutants as nitrogen dioxide and carbon monoxide violating the U.S. National Ambient Air Quality Standard (NAAQS) established for outdoor air. For example, the NAAQS acceptable limit for one-hour-averaged nitrogen dioxide is 100 parts-per-billion,13 but use of a gas stove (even without cooking food on it) results in one-hour averages of nitrogen dioxide that range from 82 to 300 ppb.
Greenhouse gas trends and air quality
Despite international agreements to rein in and eventually decrease greenhouse gas emissions, their concentrations are still increasing with no signs of slowing down. For example, the latest greenhouse gas bulletin14 of the World Meteorological Organization shows nearly monotonic growth rates for carbon monoxide, and nitrous oxide, while methane growth rates appeared to stabilize around the turn of the century only to accelerate again since 2013. The reasons for these changes are still not entirely understood, but most indications reflect that both natural and anthropogenic emissions play a role.15
Increasing greenhouse gases have caused unequivocal warming of the entire climate system,16 and, as they continue to rise, the warming and subsequent impacts will continue to grow in severity. This warming will have serious air quality impacts as atmospheric chemical processes are strongly dependent on meteorological processes.17 A warmer climate will bring hotter temperatures and heat waves,18 19 larger and more frequent forest fires,20 along with other air quality and weather events that we have yet to experience.
While there are a growing number of health risks associated with human emissions of chemical species that impact air quality and the global climate, there are also an increasing number of tools being used and actions being taken to address these risks. Here are some highlights:
- Newly launched satellites and improvements to models, algorithms, and background information about the atmosphere are increasing our capacity to make observations, identify sources of emissions, and estimate emissions. For instance, the GHGSat-D satellite is capable of taking observations of individual methane (CH4) plumes with a resolution of 50x50 square meters.21 Additionally, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) spectrometer instrument—to be launched in 2022 as a geostationary satellite instrument targeting North America—is expected to provide higher spatial resolution retrievals of multiple species at high resolution (~2.1 km x 4.4 km)22 during daylight hours. Since it will be in geostationary orbit, TEMPO will be capable of continuously monitoring the air quality over the same locations throughout the day, thereby capturing important features such as the change in pollution levels due to the daily rush hours in urban areas.
- Similar advancements in observations and modeling capabilities are making it easier to understand and constrain global emissions. For instance, the rate of decrease in atmospheric levels of the stratospheric ozone-layer destroying CFC-11, which has been decreasing since the mid-1990s, has slowed.23 Research teams identified sources of CFC-11, and, using inverse modeling, traced the CFC-11 increase back to the location where the emissions occurred.
- With many countries experiencing difficulties in meeting their emission reduction targets, regional and municipal governments, along with private industry in some cases, have taken the initiative in trying to curb emissions. Initiatives like the Regional Greenhouse Gas Initiate (RGGI), a cooperative effort among nine New England and Mid-Atlantic states to collectively reduce greenhouse gas emissions from electric power generation, are demonstrating the substantial air quality-related human health co-benefits of emissions reductions.24
Over the coming years and decades, we will acquire more knowledge pertaining to the short- and long-term impacts that human emissions may have on air quality, climate change, and human health. Just as we have learned of the harm caused by compounds previously considered harmless (e.g., DDT, BPA, asbestos), we will discover new harms and threats produced through emissions and other human behavior. For instance, there does not seem to be an ozone threshold below which exposure can be deemed safe,25 and so existing air quality standards will likely be lowered in coming years and decades.
As we continue to learn about the impact of our emissions on our atmosphere, our planet, and our health, there is a continuing potential for different companies and industries to be targeted as bearing responsibility for the health and climate impacts that air pollution may be causing, and thus necessitating changes in their activities.
For instance, 2020 has been substantially disrupted by the global response to the coronavirus pandemic, with nations implementing–to varying degrees of success–stringent lockdown policies. Subsequently, nearly every aspect of human behavior– work, school, travel– has been severely affected with regional/global economies shrinking as a result. The sometimes drastic reductions in emissions led to improvements in local air quality and ultimately raised awareness of how modern-day human activity contributes to significant levels of pollution. Additionally, this ad hoc experiment may have highlighted possible solutions for how air quality can be improved. For one thing, policies that encourage remote work even after the pandemic threat recedes could help lock-in reductions in transportation emissions, reducing both short-term pollution risks and longer-term greenhouse gas emissions.
Benjamin Brown-Steiner, is a staff scientist, Atmospheric and Environmental Research (AER) at Verisk. Benjamin can be reached at email@example.com.
Archana Dayalu, is a staff scientist, AER at Verisk. Archana can be reached at ADayalu@aer.com.
Jennifer Hegarty is a staff scientist, AER at Verisk. Jennifer can be reached at JHegarty@aer.com.
Karen Cady-Pereira is a principal scientist, AER at Verisk. Karen can be reached at firstname.lastname@example.org.
Thomas Nehrkorn is a principal scientist, AER at Verisk. Thomas can be reached at TNehrkor@aer.com.
Matthew Alvarado is vice president of the research and development division, AER at Verisk. Matthew can be reached at email@example.com.
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