Heat waves are long periods of scorching weather becoming more common and severe due to climate change. In the United States, heat waves have increased from two per year in the 1960s to six per year in recent decades. Almost every heat wave is hotter and longer because of human-caused greenhouse gas emissions. Understanding how heatwaves amplify urban air quality issues is crucial, as they increase temperatures and worsen air quality in cities, making the problem even more severe.

As global temperatures rise, cities face more frequent heatwaves, which increase air pollution. Since 1990, more people, especially older people, have become vulnerable to extreme heat. In 2021, an estimated 345 million people over the age of 65 were exposed to heatwave events.

Understanding how heatwaves amplify urban air quality issues is crucial to reduce health risks. This article will discuss how heat waves worsen air quality, their health impacts, and mitigation strategies.

Understanding the Heatwaves

A heatwave occurs when temperatures rise much higher than usual for several days or weeks. There is no universal definition for heat waves, as regions and countries use different criteria based on local conditions. One standard definition is the Heat Wave Duration Index.

The Heat Wave Duration Index defines a heat wave as five consecutive days on which temperatures exceed the maximum by 5°C (9°F), using the 1961-1990 averages.

Factors Contributing to Heatwave Formation

Heat waves are primarily caused by high-pressure systems that trap warm air in a particular area, preventing it from dissipating. These high-pressure systems, known as anticyclones, create a heat dome by forcing air to sink and compress, increasing surface temperatures.

The lack of cloud cover under these high-pressure systems allows for more solar radiation, further heating the ground and the air above it.

A heat dome is a high-pressure system that can lead to heat waves. It occurs when an area of high-pressure traps hot ocean air like a lid or cap. This causes the air to sink and become compressed, resulting in scorching temperatures lasting for days or weeks.

Other factors contributing to heatwave formation include urbanisation and land-use changes. With their dense infrastructure and limited green spaces, urban areas experience the urban heat island effect, with higher temperatures than surrounding rural areas.

This effect can amplify the intensity and duration of heat waves in cities. Land-use changes, such as deforestation & agriculture, can also influence local climates by altering the surface energy balance, affecting local temperature and humidity levels.

How Heatwaves Amplify Urban Air Quality Issues?

Heatwaves cause discomfort and harm urban air quality by increasing ozone and particulate matter (PM) levels. There are two mechanisms linking heatwaves to air quality deterioration, which are as follows:

Ozone Formation

Ground-level ozone, a harmful pollutant, causes respiratory and heart problems. It forms when sunlight reacts with nitrogen oxides (NOx) and volatile organic compounds (VOCs) found in cities. High temperatures and intense sunlight during heatwaves increase these reactions, raising ozone levels.

Heat waves also reduce wind speeds, trapping pollutants and allowing ozone to build up. During heat waves, ozone levels can rise more than usual, often exceeding the World Health Organization’s safety guideline of 100 µg/m³ for 8 hours of exposure.

Particulate Matter (PM) Concentration

Heatwaves also raise levels of PM 2.5, tiny particles that enter the lungs and bloodstream. Stagnant air during heatwaves allows PM to accumulate. Wildfires, which become more frequent during dry heatwave conditions, release large amounts of PM into the air. Heatwaves increase the risk of wildfires, creating a cycle that worsens air quality.

In 2018, long-term PM 2.5 exposure was linked to one in five global deaths, with 350,000 deaths in the U.S. alone. The combination of stagnant air, human pollution, and wildfires during heatwaves raises PM 2.5 to dangerous levels. It highlights the need for better air quality management during heatwaves to protect public health.

Also Read: Ecological and Gendered Asymmetries in Climate-Induced Displacement

Health Impacts of Poor Air Quality During Heatwaves

As heatwaves grow more intense, poor air quality poses serious health risks. Combining high temperatures with pollutants like ozone and particulate matter (PM) leads to more illness and death. According to the World Health Organization (WHO), heatwaves caused around 489,000 deaths each year globally from 2000 to 2019. Understanding these health risks is vital to addressing them.

Health Risks from Increased Ozone and PM Levels

During heatwaves, ozone levels rise and worsen respiratory problems. People may experience coughing, throat irritation, and shortness of breath. Ozone can also trigger asthma, reduce lung function, and increase hospital visits for breathing issues.

Particulate matter (PM), especially PM 2.5, causes additional health risks. These fine particles can reach deep into the lungs and bloodstream, leading to heart problems, lung diseases, and even early death.

WHO notes that long-term PM 2.5 exposure is responsible for millions of deaths each year. Heatwaves worsen air quality by trapping PM in stagnant air, increasing health risks.

Vulnerable Populations

Certain groups face higher health risks during heatwaves:

• Children: Kids are more vulnerable due to developing lungs and more outdoor play. Their smaller lungs and faster breathing expose them to more pollutants, worsening conditions like asthma.
• Elderly: Older adults, especially those with heart or lung problems, face greater danger during heatwaves. Many heat-related deaths involve older people. Centers for Disease Control and Prevention (CDC) reports 10,500 heat-related deaths in the U.S. from 2004 to 2018, with older adults at higher risk.
• People with Health Conditions: Those with chronic illnesses, like diabetes or heart disease, face increased risk during heatwaves. Extreme heat worsens health conditions, leading to more hospitalisations and deaths.

Heatwaves Mitigating Strategies

Mitigating heatwaves is crucial for protecting public health, cities, and the environment. As climate change increases heatwaves, we need effective strategies at multiple levels. Here are some key strategies:

1. Urban Planning and Infrastructure

• Green and Cool Roofs: Green roofs with plants and cool roofs with reflective surfaces lower building temperatures and reduce heat islands. They also cut down energy use for cooling.
• More Green Spaces: Expanding parks and planting trees in cities provides natural cooling, improves air quality, and creates spaces for residents.
• Permeable Materials: Using permeable materials in streets and pavements reduces heat buildup and improves water drainage.
• Better Building Designs: Buildings with natural ventilation, shading, and insulation lower indoor temperatures, reducing the need for air conditioning.

2. Public Health Initiatives

• Early Warning Systems: Alert systems warn people about heat waves, allowing them to take precautions like staying indoors and hydrated.
• Public Education: Educating people about heat risks and safety measures helps reduce heat-related illnesses.
• Cooling Centers: Public cooling centres offer a safe space for vulnerable individuals during heat waves, providing air conditioning and health support.
• Emergency Response Plans: These plans protect high-risk groups, such as the elderly and those with health issues, during extreme heat.

3. Energy Efficiency and Sustainability

• Renewable Energy: Shifting to solar and wind energy reduces greenhouse gas emissions and dependency on fossil fuels.
• Energy-Efficient Technologies: Promoting energy-efficient cooling systems manages higher energy demands during heatwaves while reducing emissions.
• Sustainable Practices: Encouraging water-saving and crop diversification practices helps manage the effects of heatwaves on agriculture.

By adopting these strategies, we can reduce heatwave impacts on cities, improve public health, and combat climate change.

Wrap Up

Due to climate change, heat waves are becoming more frequent and severe, worsening air quality in cities. They increase harmful pollutants like ozone and particulate matter (PM), posing severe health risks, especially for vulnerable populations like children, the elderly, and people with existing health conditions. The combination of extreme heat and poor air can lead to respiratory and heart problems and increased hospital visits and deaths.

To mitigate these effects, cities can adopt strategies like green roofs, more green spaces, and better building designs. Public health initiatives, such as early warning systems and cooling centres, also play a crucial role in protecting people. Moving toward renewable energy and energy-efficient technologies will help combat the root causes of heat waves and improve air quality.

Taking action now is essential to reducing the harmful impacts of heat waves and ensuring a healthier future for all.

Also Read: Real-World Impacts of Climate Change on Marginalized Communities