8 Urban Air Quality | Environmental Problem Solving in an Age of Climate Change: Volume 1

Poor air quality harms both environmental quality and human health. Nowhere are these impacts more apparent than in urban areas, where a perfect storm of vehicle exhaust, emissions from power generation, industrial pollution, and emissions from fuel used to heat homes forms in areas where human populations are high. Often, it is the most vulnerable populations which suffer from poor air quality, resulting in increased risk of stroke, heart disease, lung cancer, and chronic and acute respiratory diseases like asthma. In this unit, you’ll explore the connections between climate change and air quality in urban areas.

The Problem

With large numbers of people living in close proximity to a variety of air pollution sources, it is no surprise that major urban areas grapple with poor air quality, whether it’s brown smog largely attributable to Los Angeles traffic or gray smog formed by emissions from China’s coal-fired power plants.

These conditions are often exacerbated by natural sources that can degrade air quality; for example, schools in two Indonesian cities were closed in 2019 due to smoke from forest and peat fires .

Fine and small particulate matter (PM_2.5 and PM₁₀), including sulfates, nitrates and black carbon, ground level ozone , and a number of additional inorganic and organic compounds can harm human health.

Emissions from vehicles contribute to levels of these common pollutants and are also major sources of GHG emissions and toxins like benzene that are known to cause cancer.

The World Health Organization estimated that poor ambient air quality impacted 99% of the global population in 2019, resulting in 4 million premature deaths, with residents in poorer cities most affected.

Examining data collected from 795 cities in 67 nations, the WHO reported that levels of PM in urban air samples increased by 8% in only five years , with the most troubling trends occurring in the eastern Mediterranean and Southeast Asia.

Projections from the European Environmental Agency (Figure 8.2) indicate there will be a corresponding increase in premature deaths in the coming decades.

In addition to elevating levels of criteria air pollutants , transportation also has a large carbon footprint, often because poor planning has led to vehicle-jammed streets and highways in sprawling urban and suburban areas with little alternative transport available.

The US EPA estimates that currently, transportation is the largest and fastest-growing contributor to US GHG emissions.

The Role of Climate Change

Data from the US EPA (2018) underscore how much gasoline and diesel-powered vehicles contribute to climate change.

While vehicle emissions contribute significantly to climate change, climate change also impacts air quality in many ways.

Some of these connections between warming temperatures and air quality are obvious.

In addition to the direct and indirect effects that climate change may have on urban air quality, it is important to recognize that there is also a positive feedback mechanism at work .

Solutions

City managers have established an Ultra –Low Emission Zone (ULEZ) in the center of the city where vehicles either meet a strict emission standard or pay both a daily usage fee and a daily Congestion Charge fee for driving in the most congested portions of the city during workday hours.

Despite such efforts, the majority of vehicles in most US cities are SOVs. San Jose CA found that SOV use declined only slightly below 80% in recent years despite such efforts.

Mass transit: From city buses to monorails, cities are increasingly focused on developing mass transportation options that get people out of their cars, reducing environmental impacts.

For example, the Las Vegas, NV monorail is estimated to have eliminated over 25 million vehicle miles since it began operation in 1995.

There has been an explosion of new technologies for propelling motor vehicles.

Electric, plug-in hybrid electric, and hybrid vehicles are becoming more popular, particularly with the success of companies like Tesla and Rivian . Tesla estimates that its electric vehicles had eliminated 5 million metric tons of CO₂emissions by 2020.

But while alternative fuel vehicles powered by ethanol, biodiesel, natural gas, and fuel cells may be cleaner options than gas and diesel, they come with their own set of environmental issues.

There is a growing consensus that better urban planning is critical for mitigating climate change.

Smart planning that includes a range of transportation choices and walkable neighborhoods can help improve air quality and reduce GHG emissions.

Long-existing examples like BEDZED in the UK show that such approaches can work.