Air

By Noah McDaniel

As of 2016, over 80% of the world’s urban population are living in areas with air quality levels that exceed the limits set by the World Health Organization.¹ If this is not already troubling enough, the Intergovernmental Panel on Climate Change (IPCC) predicts with high confidence that global climate change caused by air pollutant emissions in the 21st century will lead to increasing ill-health, especially in developing regions.² This is in conjunction with local pollution, such as smog and black carbon, that makes urban air dangerous to breathe. Additionally, greenhouse gas emissions have increased with industrialization, leading to atmospheric concentrations of carbon dioxide, methane, and nitrous oxide that are unprecedented in at least the last 800,000 years.² It is believed to be extremely likely that human emissions have been the dominant cause of observed climate warming and its associated effects.² It is imperative that these trends are reversed so that the global cities of 2050 are both healthful and sustainable. Without action to reduce all forms of air pollution, from local air contaminants to those that cause global climate change, the devastation could be incredibly far-reaching, negatively affecting not only local air quality and health but sea level rise, extreme weather events, global food and water security, economic growth and the alleviation of poverty, and mass migrations.²

There are many different measurements that can be considered in determining urban air quality, both temporal and spatial. For the purposes of this Mission, ideal air quality for a future city of 2050 is defined as meeting the WHO air quality standards of 20 ug/m³ of particulate matter 2.5 (PM_2.5),³ which are particulates that are less than 2.5 microns long and can travel deeply into the respiratory system.⁴ Reaching ideal air quality also involves the mitigation of emissions of pollutants that cause ill-health effects, namely the six criteria air pollutants as identified by the EPA (ground level ozone, CO, sulfur dioxide, PM, lead, and nitrogen dioxide).⁵ Additionally, there should be significantly-reduced emissions of both long and short-lived anthropogenic forcers (external influencers of climate) that cause climate change, like CO₂, black carbon, methane, and HFC’s, among others. To put this quantitatively, CO₂ equivalent emissions should be below 500 ppm by 2050, taken from a positive mitigation scenario from IPCC.² The rationale behind this definition is to improve human health in cities while also reducing their environmental impact due to both direct and indirect emissions. This article will focus primarily on identifying the sources of pollutants and contextualizing the most major concerns associated with air quality and pollution.

It is necessary to first identify the sources of air pollutants. We define air pollutants to be “those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects.”⁶ The government of Canada defines three categories of air contaminants: biological, chemical, and radiological,⁷ but we will focus on chemical due to their dual effects on both human health and climate. Sometimes, air pollution occurs naturally; this is seen in the cases of volcano eruptions, forest fires, and dust storms.⁸ Specifically, forest fires release CO₂,⁹ dust storms release PM,⁸ and volcanoes release CO₂, SO₂, hydrogen sulfides, and hydrogen halides.¹⁰ According to the US Geological Survey, large release of SO₂ can actually cool global air temperatures.¹¹ The SO₂ clouds convert into sulfuric acid or sulfate aerosol, and “the sulfate aerosol layers scatter incident solar radiation and absorb emitted terrestrial radiation, warming the upper atmosphere whilst cooling the lower atmosphere.”¹² However, CO₂, hydrogen sulfides and hydrogen halides are all highly toxic in high concentrations,¹¹ and CO₂ is defined by NASA as being the most important forcer of climate change.¹³

Despite this, it is suggested that the natural output of CO₂ does little in causing global climate change,¹¹ because of the balance between natural sources of CO₂ and sinks (reservoirs that absorb CO₂ imbalances, such as forests). The imbalance between air pollutant emissions and sinks is caused by human actions. The IPCC has found with high confidence that between 1970 and 2010, the CO₂ emissions from industrial processes and the combustion of fossil fuels alone contributed about 78% of the total GHG emissions increase during that time period.²

The broad classifications of human sources could be considered to be industry, power generation, waste disposal, transportation, domestic sources, and agriculture. Industrial sources include industrial factories and incinerators, emitting heavy metals, PM, inorganic acidic gases, dioxins, and CO₂.¹⁴ These sources are often referred to as “point sources” because their physical location is stationary, as opposed to “mobile sources,” such as transportation.¹⁵ Power generation is another point source, and refers to the generation of electricity from coal, oil, gas, wood, or petroleum. Power generation can be as simple as burning a wood stove or as complex as the operation of a large electrical generation plant, and can emit SO₂, nitrous oxides, O₃, PM, and CO₂.¹⁶ Waste disposal refers to the breakdown of non-biodegradable and non-compostable biodegradable materials, releasing methane, CO₂, and NO.¹⁷ Transportation refers to the burning of gasoline, diesel, and other fuels, and the production and maintenance of the transportation. Agriculture emits through agricultural burning, land clearing, and other man-made fires.¹⁸

Of most importance to the context of our Mission are power generation, transportation, industry, and waste disposal, which directly affect the air quality of the city and the health of its inhabitants, and emit the greatest concentration of long- and short-term climate forcers. Although agricultural emissions are typically small for urban areas, this may change by 2050 as our Mission recommends the greater implementation of urban farming as a way to curb CO₂ emissions stemming from food transportation (see Urban Farming article).

In the United States, transportation is the single largest source of air pollution, contributing more than half of the CO and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into US air in 2013.¹⁹ This is especially pertinent because the United States is ranked first in historical emissions, and is ranked second out of all countries for current CO₂ emissions, all GHG emissions, and emissions per capita, respectively.²⁰ In other nations, transportation is also a large source of pollutants, especially in areas where cars without catalytic converters and/or leaded petrol are in greater use.²¹ About 30% of heat-trapping emissions come from this transportation category. Emissions from transportation release particulate matter, nitrogen oxides, CO, SO₂, hydrocarbons, and other hazardous air pollutants and GHGs.¹⁹ Particulate matter is both a direct and secondary pollutant: it is a byproduct of diesel exhaust and also accompanies the emission of hydrocarbons, nitrogen oxides, and sulfur dioxides.¹⁹

There is high confidence that air pollutant emissions will lead to a high risk of irreversible and grave global impacts, affecting things such as human health, extreme weather, global health and food security, and economic stability, without the implementation of more extreme mitigation efforts.² There is no one universal solution, but various mitigation scenarios suggest that substantial reductions in GHG emissions over the next few decades could substantially reduce many risks associated with climate change.² Mostly, improvements in technology, policy, and public education will be essential. For example, in developing countries, policy that requires the fleet to have catalytic converters would reduce non-CO₂ emissions. Another example is to improve air pollution education in developing regions (see Education article). Our group’s recommendations for solutions can be found in the additional Air articles found in this Mission. Additionally, global political cooperation will be necessary so that all countries take similar actions to reduce emissions, especially those which have historically contributed and are currently contributing the bulk of global emissions such as the United States, China, India, and Russia.²⁰

Our ultimate goal: Have global air quality be in compliance with World Health Organization standards by 2050, particularly in regards to particulate matter 2.5 pollutants, as well as uniform emission standards for greenhouse gasses.

In order to achieve this, we have developed the following categories; in each, we have analyzed the current situation and developed solutions accordingly.

Health Effects: What are the health impacts of urban air quality, and how are those impacts minimized? Our goals are to make short-term safety measures widely available to those living in polluted cities and, in conjunction with improving air quality, improve overall health.

Creating Successful Air Quality Policy: What does it take to develop a successful and implementable air quality policy? Examples of policy around the world are used to find the elements of effective and ineffective policy.

Education: What are lifestyles specific to countries in different parts of the world? We will develop a curriculum that is specific to those lifestyles to have individuals and corporations emulate more sustainable practices.

Technology: What technologies are available, or in development, to improve air quality? We explore increasing availability and use of green technology through social, economic, and political incentives.

The Environmental Effects of Air Pollution: The effects of air pollution on the environment are many. What are they, and what can be done to stop them?