Air Quality Insights: 1100 Cities, One Clear Picture

Air pollution is a significant global health and environmental issue, with almost 100% of the world's population exposed to dangerous levels of pollutants. The World Health Organization (WHO) has compiled a database of air quality data for 1100 cities across 91 countries, offering insight into the burden of diseases associated with outdoor urban pollution. This data provides estimates of air quality based on annual mean concentrations of fine particulate matter, with the aim of representing average levels across each city. The analysis reveals that many urban areas suffer from persistently elevated levels of fine particle pollution, largely from combustion sources such as power plants and vehicles. This compilation of air quality data is a vital tool for understanding and addressing the health impacts of air pollution, which include an increased risk of heart disease, stroke, cancer, and respiratory infections.

Fine particulate matter

Sources of fine particulate matter include combustion sources such as power plants and motor vehicles, as well as indoor sources such as tobacco smoke, cooking, and burning candles or incense. Outdoor particle pollution can also come from wildfires, with particles travelling long distances from their source.

The health effects of fine particulate matter exposure are significant. Short-term exposure can cause eye, nose, throat, and lung irritation, coughing, sneezing, a runny nose, and shortness of breath. Long-term exposure has been linked to more serious health issues, including heart disease, asthma, reduced lung function, lung cancer, and premature death, particularly in those with chronic heart or lung diseases. Studies have also suggested an association between long-term exposure and increased rates of chronic bronchitis.

The World Health Organization (WHO) has compiled air quality data sets for 1100 cities across 91 countries, providing estimates of air quality based on annual mean concentrations of fine particulate matter during the period from 2003 to 2010. This analysis concluded that persistently elevated levels of fine particle pollution are common across many urban areas, with the majority of urban populations exposed to annual levels exceeding the maximum recommended by the WHO Air Quality Guideline.

Disease burden

Air pollution is a major health threat across the globe. According to the World Health Organization (WHO), almost the entire global population (99%) is exposed to air pollution levels that put them at an increased risk of developing various diseases, including heart disease, stroke, chronic obstructive pulmonary disease, cancer, and pneumonia.

The WHO has released a compilation of air quality data sets for 1100 cities across 91 countries, which includes an analysis of the premature deaths caused by fine particulate matter pollution in these urban areas. This analysis found that persistently elevated levels of fine particle pollution, originating from combustion sources such as power plants and motor vehicles, are common across many cities. The majority of urban populations are exposed to annual levels of fine particle pollution that exceed the maximum recommended by the WHO Air Quality Guideline.

The disease burden attributed to air pollution is significant, with an estimated 1.34 million premature deaths attributable to outdoor air pollution in cities in 2008. Additionally, it is estimated that 1.09 million deaths could have been prevented that year if the WHO Guidelines had been universally followed. The burden of disease due to air pollution is expressed in terms of deaths and disability-adjusted life years (DALYs), which take into account not only early deaths but also the number of years lived in poor health.

The impact of air pollution on health is not limited to a specific region or country, but it tends to be greater in low and middle-income countries. This is due to a combination of high indoor pollution rates in low-income countries, often due to the use of solid fuels for cooking, and increasing outdoor air pollution as countries industrialize and transition to middle-income status. Literature reviews by organizations such as the US Environmental Protection Agency and the WHO have shown that long-term exposure to air pollution increases mortality and morbidity from cardiovascular and respiratory diseases, lung cancer, and shortens life expectancy.

Quantifying the health burden associated with air pollution is crucial for guiding decision-making and emphasizing the need to improve air quality to promote public health. The WHO and other organizations continue to monitor and assess the exposure levels and health impacts of air pollution at the national, regional, and global levels, providing valuable data for official reporting and policy-making.

Air quality standards

In 2011, the World Health Organization (WHO) released a database containing air quality data for 1100 cities across 91 countries. The data provides an estimate of air quality based on the annual mean concentrations of fine particulate matter in cities between 2003 and 2010. Fine particulate matter can be extremely harmful to health, causing heart disease, lung cancer, asthma, and acute lower respiratory infections.

The WHO's analysis of the data concluded that persistently elevated levels of fine particle pollution are common across many urban areas, often originating from combustion sources such as power plants and vehicles. Furthermore, the majority of urban populations are exposed to annual levels of fine particulate matter in excess of the maximum recommended by the WHO Air Quality Guideline.

To address air pollution and its associated health risks, governments and organizations have established air quality standards to regulate and improve air quality. For instance, the United States Environmental Protection Agency (EPA) has set National Ambient Air Quality Standards (NAAQS) for six principal outdoor air pollutants ("criteria pollutants") under the Clean Air Act. These criteria pollutants include particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). The NAAQS are designed to protect public health and the environment, with primary standards focused on safeguarding the health of sensitive populations, and secondary standards aimed at preserving public welfare and natural resources.

The EPA also establishes an Air Quality Index (AQI) for the five major air pollutants regulated by the Clean Air Act. The AQI provides a numerical value that indicates the level of air pollution, with higher values representing greater pollution and health concerns. For instance, an AQI value of 50 or below suggests good air quality, while an AQI over 300 indicates hazardous air quality.

By setting and periodically reviewing air quality standards, organizations like the WHO and EPA aim to minimize the harmful impacts of air pollution on human health and the environment, ultimately improving the well-being and longevity of populations in cities around the world.

Indoor air pollution

The World Health Organization (WHO) has released air quality data for 1100 cities across 91 countries, including an analysis of the burden of disease associated with urban outdoor pollution. The data reveals that persistently elevated levels of fine particle pollution are common across many urban areas, originating from combustion sources such as power plants and motor vehicles. The analysis also estimates that 1.34 million premature deaths in 2008 were attributable to outdoor air pollution in cities.

While the WHO database focuses on outdoor air pollution, indoor air pollution is equally important to address. Indoor Air Quality (IAQ) refers to the air quality within and around buildings, particularly as it relates to the health and comfort of the occupants. Indoor pollution sources that release gases or particles into the air are the primary cause of poor IAQ. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions and by failing to carry indoor pollutants out of the enclosed space. High temperatures and humidity levels can also increase certain pollutant concentrations.

There are many sources of indoor air pollution, including building materials, household cleaners, and biological pollutants such as dust mites and pet dander. The use of polluting fuels and stoves for cooking can also significantly contribute to indoor air pollution. Around 2.1 billion people worldwide rely on open fires or inefficient stoves fuelled by kerosene, biomass (wood, animal dung, crop waste), or coal for cooking, which generates harmful household air pollution. Women and children, typically responsible for household chores, bear the greatest health risks from the use of these polluting fuels and technologies.

The health effects of indoor air pollutants can be experienced soon after exposure or even years later. Immediate effects may include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. These symptoms are usually short-term and treatable, sometimes requiring only the elimination of the person's exposure to the pollution source. However, pollutants commonly found in indoor air can also cause more severe and long-term health issues, including respiratory diseases, heart disease, and cancer. It is important to understand and control common indoor pollutants to reduce the risk of adverse health outcomes.

To address indoor air pollution, the WHO has developed the "Guidelines for Indoor Air Quality: Household Fuel Combustion." These guidelines offer practical, evidence-based recommendations on the types of fuels and technologies that protect health and provide strategies for transitioning to cleaner household fuels and technologies. The guidelines discourage the use of kerosene and unprocessed coal and emphasize the benefits of clean fuels and technologies such as solar, electricity, biogas, liquefied petroleum gas (LPG), natural gas, alcohol fuels, and biomass stoves that meet emission targets.

Outdoor air pollution

WHO's Air Pollution Data Portal includes an extensive database of air quality data from 1100 cities across 91 countries. This database provides valuable information on the levels of outdoor air pollution in urban areas and the associated health risks. The data is collected by monitoring stations that measure particulate matter (PM2.5 and PM10), Ozone (O3), Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2), and Carbon Monoxide (CO) emissions.

The analysis of the data from these 1100 cities has revealed several key findings. One of the most concerning conclusions is that persistently elevated levels of fine particle pollution are common across many urban areas. This type of pollution originates from combustion sources such as power plants and motor vehicles. As a result, the majority of urban populations are exposed to annual levels of air pollution that exceed the maximum recommended by the WHO Air Quality Guidelines.

The impact of outdoor air pollution on health is significant. For example, it has been estimated that in 2008, approximately 1.34 million premature deaths were attributable to outdoor air pollution in cities. Furthermore, it is believed that if the WHO guidelines had been universally met that year, around 1.09 million of those deaths could have been prevented. These findings highlight the urgent need to address outdoor air pollution to protect public health.

While air pollution levels have decreased in some high-income countries, such as the UK and the US, the issue remains prevalent in many low-to-middle-income countries. Today's megacities, particularly those in low-to-middle-income countries, face the challenge of managing development and urbanization while mitigating air pollution. Historical data shows that as cities industrialize, pollution levels tend to rise, peak, and then eventually decline. However, the health burdens of air pollution in rapidly developing cities are significant, and solutions are needed to accelerate the process of reducing pollution levels.

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