Air Pollutants: Heating Up The Planet

Air pollution and temperature are deeply interconnected. Rising temperatures can increase the production of certain air pollutants, while air pollutants can also contribute to rising temperatures. This complex relationship has significant impacts on human health, the environment, and the climate. Understanding the interplay between temperature and air pollution is crucial for developing effective solutions to mitigate their harmful effects.

The movement of air pollution is influenced by air temperature

During the summer, warm air lifts pollution away from the surface. However, in the winter, a temperature inversion can occur, where a layer of warm air traps cold air and pollution close to the ground. This phenomenon is more common in cities situated in mountain basins or valleys, such as Los Angeles, Denver, and Mexico City. Consequently, air pollution tends to be more severe in these regions during the colder months.

The temperature also affects the visibility of air pollution. In cold weather, vehicle exhaust, chimneys, and smokestacks are more visible. This increased visibility is due to both the higher concentration of pollutants in the air and the fact that warm vapour exhaust is more visible in colder temperatures. Additionally, people tend to burn more fuel for heating and idle their cars for longer periods during winter, leading to increased air pollution.

Furthermore, the formation of certain pollutants, such as ground-level ozone, is favoured by warmer temperatures. Ozone is a greenhouse gas that contributes to climate change by trapping heat in the atmosphere. Climate change, driven in part by air pollution, can then further exacerbate temperature rise, creating a positive feedback loop.

While the impact of temperature on air pollution is complex, it is clear that the two are intricately linked. Understanding this relationship is crucial for developing strategies to mitigate the negative consequences of air pollution and climate change on human health and the environment.

Temperature inversions can trap pollution at the surface

Temperature inversions, also known as weather inversions or thermal inversions, occur when the normal temperature gradient of the atmosphere is reversed. Typically, the air near the ground is warm, and the atmosphere gets colder with increasing elevation. During a temperature inversion, cold air is trapped beneath warm air, creating a pocket of stagnant air close to the Earth's surface.

Thermal inversions are more common than one might think. For instance, waking up to a blanket of fog in low-lying areas and dew on the grass is a sign of a temperature inversion. Temperature inversions usually dissipate with wind or when the surface begins to warm up again the next day. However, when temperature inversions persist, the pollutants trapped beneath the warm air layer can create hazardous air quality conditions.

The weather's impact on air pollution is undeniable, and temperature inversions play a significant role in this dynamic. Typically, rising warm air near the ground lifts pollution away, dispersing it. However, during a temperature inversion, the warm air is unable to rise, trapping pollution at the surface. This phenomenon is known as a thermal inversion, and it occurs when a layer of warm air traps cool air and pollution close to the ground.

Thermal inversions are more prevalent above cities located in mountain basins or valleys, such as Los Angeles, Denver, and Mexico City. In these areas, cold, dense air becomes trapped, and the warm air acts like a lid, preventing the escape of pollutants. This stagnant air allows pollutants such as vehicle and factory exhaust to concentrate over an area, negatively impacting air quality.

Additionally, temperature inversions can have significant health consequences. The trapped pollutants can worsen existing respiratory and heart diseases and trigger illnesses such as asthma, chronic obstructive pulmonary disease (COPD), and bronchitis. Certain socially vulnerable groups, including Black and African Americans, low-income communities, Indigenous populations, and immigrants, are at higher risk of experiencing the detrimental health effects of air pollution due to temperature inversions.

Rising temperatures can increase ground-level ozone

Ground-level ozone is not directly emitted into the air but is formed by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs). These reactions occur when pollutants from cars, power plants, industrial boilers, refineries, and chemical plants chemically react in the presence of sunlight. Therefore, hot and sunny days, especially during heatwaves, can increase ground-level ozone levels, causing it to reach unhealthy levels.

The impact of rising temperatures on ground-level ozone is a significant concern, as it can lead to more frequent and intense "ozone alert" days. Higher temperatures result in stagnant air, preventing the dispersal of pollutants and trapping them at the surface. This phenomenon, known as thermal inversion, is more common in cities located in mountain basins or valleys, such as Los Angeles, Denver, and Mexico City.

The increase in ground-level ozone due to rising temperatures poses a threat to human health and the environment. It can negatively affect sensitive vegetation and ecosystems, including forests, parks, and wildlife refuges. Additionally, the economic implications of ozone pollution are significant, with costs associated with sick days and emergency room visits.

To address the issue of rising ground-level ozone, it is crucial to implement strategies to reduce emissions of pollutants that contribute to its formation. This includes regulating emissions from vehicles, power plants, and industrial sources. By taking proactive measures, we can mitigate the impact of rising temperatures on ground-level ozone levels and protect the health and well-being of communities affected by this harmful pollutant.

Heatwaves and air pollution can have a deadly combination

Heatwaves and air pollution are indeed a deadly combination. The combination of the two is worse for human health than either heatwaves or air pollution alone. The risk of death on extremely hot and polluted days is about three times greater than on days with only high heat or only high air pollution. The more extreme the temperatures and pollution, the higher the risk. During the top 1% of the hottest and most polluted days, the risk of death increased by 21%. Among older adults over the age of 75, the risk of death increased by more than a third on those days.

There are several ways that the combined exposure to extreme heat and particulate air pollution can harm human health. Oxidative stress is the most common biological pathway linked with particulate air pollution and heat exposure. Oxidative stress is an imbalance between the production of highly reactive molecules known as reactive oxygen species, or ROS, and the body’s ability to remove them.

Heatwaves often lead to poor air quality. The extreme heat and stagnant air during a heatwave increase the amount of ozone pollution and particulate pollution. Drought conditions can also occur during a heatwave, drying out soils. During a drought, forest fires are more common. Fires add carbon monoxide and particle pollution to the atmosphere. The 2018 Kiwah fire in Idaho, for example, resulted from a lightning strike. Due to dry weather conditions, the fire persisted for over two months and covered just over 14,000 acres.

The effects of climate change on air quality will continue to vary by region. In many areas of the United States, climate change is expected to worsen harmful ground-level ozone, increase people’s exposure to allergens like pollen, and contribute to worsening air quality. Hot, sunny days can increase the amount of ozone at ground level. In 2021, the U.S. Southwest experienced one of the most severe long-term droughts of the past 1,200 years. Dust from droughts can increase particulate matter and cause air quality issues.

In addition, climate change has already led to more frequent wildfires and a longer wildfire season. Wildfire smoke pollutes the air, impairing visibility and disrupting outdoor activities. It can also spread hundreds of miles downwind to other regions. Exposure to wildfire smoke can worsen respiratory illnesses, such as asthma, chronic obstructive pulmonary disease (COPD), and bronchitis. Wildfire smoke exposures have also been linked to premature births.

Reducing emissions can help curb temperature increases

Reducing emissions is crucial to curbing temperature increases and mitigating the impacts of climate change. Climate change is primarily driven by the accumulation of greenhouse gases in the Earth's atmosphere, leading to the planet warming up. The burning of fossil fuels, such as coal, gasoline, and natural gas, for energy production, transportation, and industrial processes, is a significant source of these emissions.

By reducing emissions from these sectors, we can slow down the rate of climate change and its associated effects on temperature. Power plants, factories, farms, and vehicles are major contributors to greenhouse gas emissions. Transitioning to renewable energy sources, such as wind, solar, and hydropower, can significantly reduce emissions from power plants and factories. Additionally, improving energy efficiency in these sectors can further curb emissions.

In the transportation sector, encouraging the use of electric vehicles, hybrid cars, and alternative fuels can reduce emissions from cars, ships, and planes. Promoting public transportation, carpooling, biking, and walking can also lead to fewer vehicles on the road and lower greenhouse gas emissions. Similarly, in the agricultural sector, adopting sustainable farming practices and reducing methane emissions from livestock can help curb emissions.

Reducing emissions from fossil fuel combustion will not only help curb temperature increases but also improve air quality and human health. Air pollution from burning fossil fuels, such as sulfur and nitrogen oxides, contributes to respiratory illnesses and premature deaths. By reducing these emissions, we can improve public health and prevent economic losses associated with climate change.

Additionally, forests, oceans, and soil act as carbon sinks, absorbing and storing carbon dioxide from the atmosphere. Protecting and restoring these natural ecosystems can help reduce the amount of carbon dioxide in the atmosphere, contributing to curbing temperature increases. Overall, reducing emissions across various sectors is essential to mitigate climate change and its impacts on temperature, human health, and the environment.

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