The Dark Side Of Downtown: Uncovering Pollution Sources

Downtowns are a major source of pollution, with urban residents worldwide breathing in unhealthy levels of pollution. Urban air pollution is caused by anthropogenic activities, including transportation, domestic fossil fuel use, industrialization, power generation, combustion, and agriculture. The use of private vehicles, particularly older diesel models, is the primary source of urban air pollution. Vehicle emissions, including nitrogen dioxide (NO2) and particulate matter (PM), are the most significant contributors to poor air quality in cities. In addition to transportation, other sources of pollution in downtown areas include construction, commercial cooking, wood-burning, and boilers. Climate change also plays a role in urban air pollution, as heatwaves increase natural volatile organic compound (VOC) emissions from plants and photochemistry, leading to higher ozone and secondary particulate matter concentrations.

Vehicle emissions

The personal automobile is the single greatest polluter in urban areas. The emissions from vehicles include various gases and particles, such as carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides, and particulate matter (PM). CO2 emissions are directly proportional to fuel consumption, with a 1% increase in fuel consumption resulting in a corresponding 1% increase in CO2 emissions. Passenger cars and light-duty trucks also emit small amounts of other greenhouse gases, making their total emissions slightly greater than just CO2.

Traffic congestion plays a significant role in increasing vehicle emissions and degrading air quality. Studies have shown excess morbidity and mortality for drivers, commuters, and individuals living near major roadways. Recurring congestion, such as rush-hour traffic, can result in repeated and chronic exposure to pollutants, increasing long-term health risks. The risks are influenced by various factors, including traffic volume, vehicle mix, road type, and meteorology.

The design of downtown areas can also impact the concentration of vehicle emissions. Tall buildings on either side of a street can create a "street canyon" effect, where the street is sheltered from wind, restricting airflow and allowing pollution to build up. This can trap pollution from road vehicles, leading to higher levels of harmful emissions in downtown areas.

To reduce vehicle emissions and improve air quality, individuals can opt for more fuel-efficient vehicles, maintain their vehicles, and practice efficient driving habits. Electric, hybrid, and compact fuel-efficient gas vehicles can help reduce pollution, and proper maintenance ensures that emission controls are functioning correctly. Observing speed limits, accelerating gradually, and avoiding excessive idling can also lower emissions. Additionally, local policies and regulations can play a crucial role in reducing vehicle emissions and improving air quality in downtown areas.

Industrial emissions

The impact of industrial emissions on downtown areas is extensive. Firstly, they contribute to ambient (outdoor) fine particle air pollution (PM2.5) and nitrogen dioxide (NO2) levels. The small size of PM2.5 particles, measuring 2.5 micrograms or smaller, allows them to easily penetrate the lungs and even enter the bloodstream, posing various health risks. Industrial emissions are a primary source of these harmful particles, along with vehicle emissions, coal-burning power plants, and other sources.

Secondly, industrial emissions have a disproportionate impact on certain demographic groups. Studies have shown that neighbourhoods with higher populations of African Americans, Hispanics, and Latinos, as well as individuals with limited education or experiencing poverty, are more likely to be exposed to carcinogenic chemicals from industrial facilities. This inequity in exposure may contribute to observed cancer disparities among these demographic groups.

Additionally, industrial emissions in downtown areas can have long-term effects on the health and well-being of residents. Long-term exposure to pollutants can lead to respiratory and cardiovascular diseases, decreased lung function, increased frequency of asthma attacks, and other respiratory illnesses. The concentration of industrial activities and emissions in downtown areas can exacerbate these health risks for residents.

Furthermore, industrial emissions contribute to environmental degradation, including acid rain and climate change. Acid rain results from the emission of sulphur dioxide and nitrogen oxides, which react with water vapour in the atmosphere to form acid droplets. Climate change is influenced by the release of greenhouse gases, such as carbon dioxide and methane, from industrial processes, leading to global warming and altering weather patterns.

Fossil fuel burning

Fossil fuels, such as oil, coal, and gas, have been the primary energy source for over a century, serving about 80% of our energy needs even today. The burning of these fuels releases harmful gases and particles into the atmosphere, contributing to air pollution, water pollution, and plastic pollution.

Air pollution from fossil fuel burning has severe health implications, causing asthma, cancer, heart disease, and premature death. The combustion of additives in gasoline produces ultra-fine particles and aromatic hydrocarbons, which are carcinogenic. Globally, one in five deaths is attributed to fossil fuel pollution, with 350,000 premature deaths in the United States in 2018 alone. The toxins released during burning, such as benzene and formaldehyde, are linked to blood disorders and childhood leukemia.

When fossil fuels are burned, they emit nitrogen oxides, which contribute to smog and acid rain formation. These compounds adversely affect air, land, and water quality. The excess nitrogen deposited back onto land washes into nearby water bodies, leading to harmful algal blooms and oxygen-deprived aquatic zones, which are toxic to aquatic life. Additionally, the burning of fossil fuels releases carbon, making it the primary driver of global warming and climate change.

Climate change, caused by burning fossil fuels, leads to more frequent and severe weather events, including wildfires, hurricanes, wind storms, flooding, and droughts. These events have had significant financial impacts, with a cost of $606.9 billion in the United States between 2016 and 2020. Moreover, oceanic and atmospheric warming due to climate change contribute to global sea level rise, resulting in increased flooding, destructive storm surges, and saltwater intrusion.

To mitigate the environmental and health impacts of fossil fuel burning, a transition to renewable and clean energy sources is imperative. While progress has been made in scaling up renewable energy and improving energy efficiency, it is crucial to continue implementing regulations and incentives that promote sustainable practices and reduce harmful emissions.

Construction

The type of dust created on construction sites varies, with some types, such as silica and asbestos, posing greater air pollution risks than others. Asbestos, in particular, is one of the most dangerous forms of construction waste. When asbestos-containing materials degrade or are not properly contained during construction, they can be released into the air and inhaled, causing significant damage to human health. Wooden dust is also common due to the drilling of wood during construction, and silica dust and other toxic fibres can have long-term effects on the lungs.

Water used during construction for concrete mixing or site cleanup can become polluted and should be treated properly to prevent contamination of local water bodies. Common liquids like cement, paint, and glue found in liquid waste at construction sites can cause water pollution if not managed correctly. Soil pollution can also occur if hazardous materials are uncovered or spilled during construction, compromising soil health and the health of the supported ecosystem.

Commercial cooking

In a study conducted by scientists in Minnesota, it was found that commercial cooking appliances such as oven-cooked pizzas, steaks cooked in a broiler, and hamburgers cooked on a griddle or charcoal fire produced varying levels of emissions. Fatty foods cooked with high heat, especially with open flames, were found to create the most emissions. For example, for every 1,000 pounds of hamburger cooked on conveyor broilers, 25 pounds of emissions were created, while the same weight of pepperoni pizza cooked in an oven created just three pounds of emissions. The use of certain oils can also increase emissions, such as cooking 1,000 pounds of chicken in a wok with peanut oil, which produced 45 pounds of emissions.

In London, commercial cooking contributes significantly to PM emissions, accounting for 15% of the total in the city. In the London Borough of Camden, commercial cooking is the single largest source of this type of air pollution, contributing 39% of PM. Studies from Thailand to Norway have also concluded that restaurant workers are more at risk of respiratory illnesses due to their exposure to pollution.

To mitigate the impact of commercial cooking on air pollution, some regions in California have implemented restrictions on commercial cooking emissions, requiring the use of catalytic converters to minimize the release of aerosol particles from charbroiler grates. Additionally, experts recommend using an extractor fan when cooking due to the spike in air pollution the activity can cause.

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