Air Quality Today: Is It Safe To Breathe?

Air quality is a critical aspect of public health, and it varies from place to place. For instance, New York City, despite being the most populous city in the United States, has relatively clean air on average. In contrast, Hamburg has very unhealthy air quality. Various factors, such as vehicle emissions and industrial activities, contribute to air pollution, and governments are taking measures to improve air quality, such as transitioning to electric vehicles and implementing pollution control programs. Real-time air quality data is available through interactive maps and forecasts, which are essential tools for monitoring and managing air pollution.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a tool used to communicate information about outdoor air quality and health. The AQI is calculated for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI is measured using air quality monitors that are outfitted with sensors designed to detect specific pollutants. Some monitors use lasers to scan particulate matter density in a cubic meter of air, while others rely on satellite imaging to measure energy reflected or emitted by the Earth.

The AQI is divided into six color-coded categories, each corresponding to a range of index values. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 represents hazardous air quality. AQI values at or below 100 are generally considered satisfactory, while values above 100 are unhealthy, first for sensitive groups of people and then for everyone as values increase.

According to the World Health Organization, 99% of the global population breathes unclean air, and air pollution causes approximately 7 million premature deaths annually. PM2.5, or particulate matter with a diameter of 2.5 micrometres or less, is the most significant health threat and is often used as a metric in legal air quality standards. When inhaled, PM2.5 can enter the bloodstream and has been linked to serious illnesses such as stroke, heart disease, lung disease, and cancer.

To address air pollution, individuals can make changes such as reducing vehicle usage, carpooling, and using public transportation, and choosing fuel-efficient or electric vehicles. Additionally, proper maintenance of vehicles and following refueling instructions can help reduce emissions. Communities can invest in public transportation, bike lanes, and the development of green spaces, which help improve air quality. Governments also play a crucial role in strengthening air quality regulations, improving monitoring capacity, and implementing policies to reduce emissions and protect public health.

Ozone and PM2.5/PM10

Ozone is a gas composed of three oxygen atoms. It can be found in the Earth's upper atmosphere, where it is known as stratospheric ozone, and at ground level. Stratospheric ozone is often referred to as "good" ozone as it forms a protective layer that acts as a shield from the sun's harmful ultraviolet rays. This beneficial ozone layer has been partially destroyed by man-made chemicals, creating a "hole in the ozone". However, the hole is currently diminishing.

In contrast, ground-level ozone is considered "bad" as it is an air pollutant that negatively affects people, plants, and the environment. It is the main ingredient in smog and can trigger a variety of health issues, especially for children, the elderly, and those with lung diseases such as asthma. Ground-level ozone is formed when nitrogen oxides and volatile organic compounds react with each other in sunlight and hot temperatures. The sources of these pollutants include vehicles, industry, power plants, and other emissions.

Particulate Matter (PM) refers to particle pollution, specifically fine inhalable particles or droplets. PM2.5 includes particles with a diameter of 2.5 micrometers or smaller, while PM10 refers to larger particles. These particles can be found in dust and smoke. PM2.5 particles are particularly harmful as they are small enough to travel deeply into the lungs, causing both short-term and long-term health effects, including inflammation and damage to lung tissue. PM10 particles can also compromise respiratory and cardiac health.

The Environmental Protection Agency (EPA) in the United States develops National Ambient Air Quality Standards (NAAQS) to protect public health and the environment from PM and ground-level ozone. These standards are regularly reviewed and revised based on new data to ensure the protection of public health.

Air pollution and health

Air pollution is the greatest environmental health risk in Europe and a major cause of premature death and disease. It is also the world's largest environmental risk factor for disease and premature death, responsible for approximately 9 million deaths per year, or one in every six deaths worldwide.

Air pollution is caused by a variety of sources, including residential, commercial, and institutional energy consumption, the manufacturing and extractive industries, agriculture, transport, and buildings. Outdoor air pollution comes from vehicle exhaust, smoke, road dust, industrial emissions, pollen, gas-fueled yard equipment, and chemicals used in homes. Indoor air pollution comes from radon, smoke, lead dust, carbon monoxide from faulty furnaces, mold, and volatile organic compounds from paint. Biological pollutants, such as mold, pollen, animal dander, dust mites, and cockroaches, are also indoor air pollutants that can trigger breathing problems, allergic symptoms, or asthma attacks.

The health impact of air pollution exposure depends on the duration and concentration of exposure, as well as the health status of the affected populations. Those with underlying health problems, such as heart and lung disease, are more susceptible to the negative effects of air pollution. Children, the elderly, pregnant women, and people living in low-income neighborhoods or areas with high levels of air pollution are also especially vulnerable.

The effects of air pollution on health include coughing, itchy eyes, and the worsening of many breathing and lung diseases, such as asthma, chronic obstructive pulmonary disease (COPD), emphysema, and chronic bronchitis. Air pollution can also cause respiratory infections, heart disease, stroke, lung cancer, and even premature death. It has also been linked to an increased risk of other cancers, type 2 diabetes, obesity, systemic inflammation, Alzheimer's disease, and dementia.

To address these health risks, the European Union has implemented a clean air policy and set standards for key air pollutants in the ambient air quality directives. The EU's air quality standards are currently being revised to align more closely with the World Health Organization's (WHO) recommendations. Similarly, the US Environmental Protection Agency (EPA) uses research on the health effects of air pollution to inform the required reviews of the National Ambient Air Quality Standards (NAAQS).

Climate change

The main driver of climate change is the increase in heat-trapping greenhouse gases in the Earth's atmosphere. The primary source of these gases is the burning of fossil fuels, such as coal, oil, and natural gas, for energy, industry, transport, and buildings. Other human activities that contribute to greenhouse gas emissions include deforestation, agriculture, and land-use changes. According to the UN, human activities are responsible for virtually all global heating over the last 200 years. The average temperature of the Earth's surface is now about 1.2°C warmer than it was in the late 1800s (before the industrial revolution) and warmer than at any time in the last 100,000 years. The past five years have been the warmest on record, with 2024 being the hottest year.

The consequences of climate change are already being felt around the world and include severe droughts, water scarcity, wildfires, rising sea levels, flooding, melting polar ice, catastrophic storms, and declining biodiversity. These impacts affect human health, the ability to grow food, housing, safety, and work. Climate change has also led to an increase in the number of people displaced by weather-related events, and this number is expected to rise in the future.

To mitigate the worst impacts of climate change, global temperature rise must be limited to no more than 1.5°C. This will require a rapid and significant reduction in greenhouse gas emissions, with emissions halved by 2030 and net-zero emissions achieved by 2050. This can be achieved by transitioning from fossil fuels to renewable energy sources, such as solar and wind power, and reducing the use of coal, oil, and gas. While there has been some progress in these areas, current policies point to a warming of up to 3.1°C by the end of the century, which would have devastating consequences for the planet and human society.

Indoor air quality

One of the main factors affecting indoor air quality is ventilation. Inadequate ventilation can lead to a build-up of pollutants and contaminants, such as volatile organic compounds (VOCs), which can be emitted from furniture, paint, and cleaning products. Poor ventilation can also result in increased humidity, which fosters the growth of mould and bacteria, further degrading air quality. To improve indoor air quality, it is important to ensure effective ventilation by regularly opening windows and doors, and, in more extreme cases, investing in mechanical ventilation systems.

Another factor that can influence indoor air quality is the presence of common indoor pollutants. These can include dust mites, pet dander, second-hand smoke, radon, and carbon monoxide. These pollutants can cause a range of health issues, from minor allergies and irritation to serious respiratory problems. It is important to be aware of potential sources of indoor pollution and take steps to mitigate their impact, such as regularly cleaning and vacuuming, using air purifiers, and ensuring proper ventilation.

Additionally, indoor air quality can be affected by outdoor sources, such as air pollution from traffic, industrial emissions, and natural sources like pollen and wildfires. In areas with high levels of outdoor air pollution, it is particularly important to monitor indoor air quality, as pollutants can enter buildings through open windows, doors, and ventilation systems. Using air filters and purifiers can help reduce the impact of outdoor pollution on indoor air quality.

Finally, indoor air quality can be influenced by human activities such as cooking, cleaning, and the use of personal care products. These activities can release pollutants and contaminants into the air, including particulate matter, chemicals, and odours. For example, cooking with gas stoves can produce nitrogen dioxide and carbon monoxide, which can degrade indoor air quality and pose health risks. It is important to be mindful of the potential impact of these everyday activities and take steps to minimise their effects, such as using exhaust fans, opening windows, and choosing low-emission products.

Frequently asked questions