Air Pollution Ranking In 32 Cities — How Does Yours Measure Up? (State of Pollution Series)

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As we revealed in our previous article, air pollution is a serious problem that costs millions of lives each year and is a drain on the world economy. According to the World Health Organisation (WHO) air pollution is now a bigger health threat than HIV and Ebola. You might now be wondering how your own city measures up against others from around the world, where it sits in the rankings, and what the health effects of air pollution might be.

To help answer these questions, we have used data from the WHO Ambient Air Pollution database to rank the air pollution level of 32 cities from around the world. Overall air pollution is measured by looking at the levels of a number of different common pollutants. The pollutants measured are nitrogen dioxide, sulfur dioxide, lead, ground-level ozone, carbon monoxide, and particulate matter. Each of these pollutants can cause a wide range of health problems, ranging from the respiratory and cardiovascular problems caused by ozone and particulate matter, to the neurological effects of lead pollution.

The Dangerous Effects of Particulate Matter

For the WHO Ambient Air Pollution Database, the amount of particulate matter is measured to determine the level of air pollution in almost 3,000 cities. Particulate matter is the term for a mixture of solid particles and liquid droplets that are found in the air. This includes PM2.5, which is particulate matter that is less than 2.5 micrometers in width, and PM10, which is particulate matter that is less than 10 micrometers in width. The particles can include black carbon, sulfates, mineral dust, and more, and can come from a variety of sources, such as the burning of fossil fuels or from complex chemical reactions between organic compounds. These particles are small enough to be able to enter the lungs when we breathe, and there is a body of scientific evidence that shows how long- and short-term exposure can have severe effects on the cardiovascular system, such as heart attacks and strokes, and respiratory problems, such as coughing, chest tightness, and asthma attacks.

The WHO database looks at the annual average of levels of both PM2.5 and PM10. The data can then be used to rank the cities from those with the highest level of emissions to those with the lowest. PM2.5 is the measure used as this is the most prevalent type of air pollution, and the one which has the most immediate effect on health.

New York is Cleaner than Berlin

What is interesting about this ranking is that New York appears far below Berlin. Historically speaking, New York has experienced intense problems with air pollution, such as the deadly wave of smog in 1966 that killed approximately 200 people. This incident sparked a huge increase in awareness of the health problems caused by air pollution, and led to the introduction of the 1967 Air Quality Act and the 1970 Clean Air Act. Now, New York is enjoying its best air quality in 50 years, something which is largely due to buildings changing to cleaner heating fuels. This switch has dramatically reduced the amount of sulfur dioxide in the city air, improving air quality and saving many lives as a result.

Berlin has also experienced a marked improvement in air quality over the decades. Data for the levels of PM2.5 in the air is only available from 2005, but even in this time Berlin has managed to reduce the amount of PM2.5 from 2,363 tonnes in 2005 to 1,829 tonnes in 2009. When it comes to particulate emissions from vehicle exhausts, Berlin has performed incredibly well, reducing the amount of emissions by 80% between 1989 and 2009. With this type of reduction it can be expected that Berlin will continue to move down the rankings and keep improving air quality.

The Worrying Level of Pollution in Beijing

If you’re living in Beijing, the story is different. Beijing has one of the highest levels of PM2.5 in the world, and the health risks are severe. Daily levels of PM2.5 regularly reach figures that are high enough to be considered a health problem for everyone. For example, in the 2015 Beijing Marathon, 6 people suffered heart attacks as a result of the pollution levels. PM2.5 was around 175 that day.

In general, air pollution across China has skyrocketed in the past decades, with CO2 emissions alone doubling in the 5 year period between 2000 and 2005. Action is being taken, but it’s clear that something drastic needs to happen to address the problems present in Beijing.

What the WHO data doesn’t take into account is the fact that a city might have a good annual ranking, yet can still experience days with dangerous levels of air pollution. Short-term increases in particulate matter can be caused by weather patterns and high heats that can trap the emissions from vehicles and factories. While it seems that the air quality is good over the course of a year, it can still pose a danger on any given day. Los Angeles, for example, experienced 77 days of unhealthy air quality in 2015. Of the 77 days, 7 were at a level considered unhealthy for the whole population. In the same period, San Francisco experienced 5 days of air quality that was unhealthy for sensitive persons in the population, whereas New York experienced zero.

In future articles, we’ll be looking more in depth at what individual cities are doing to tackle the problems of air pollution, and how startups and companies are helping with the process. In the meantime, check out the 32 cities with the highest/worst air pollution rankings.

Air Pollution Ranking of 32 Cities

City / Annual PM2.5 Level / Number of unhealthy particle pollution days

  1. Delhi / 122
  2. Beijing / 85
  3. Cairo / 76
  4. Shanghai / 52
  5. Yaoudé / 49
  6. Johannesburg / 41
  7. Antananarivo / 37
  8. Hong Kong / 29
  9. Bangkok / 24
  10. Seoul / 24
  11. Moscow / 20
  12. Mexico City / 20
  13. Sao Paulo / 19
  14. Brussels / 18
  15. Paris / 18
  16. Rio de Janeiro / 18
  17. Singapore / 18
  18. Manila / 17
  19. Nairobi / 17
  20. Berlin / 16
  21. Barcelona / 15
  22. London / 15
  23. Munich / 15
  24. Los Angeles / 11 / 77
  25. Madrid / 10
  26. Washington DC / 10
  27. San Francisco / 9 / 5
  28. New York / 9 / 0
  29. Toronto / 8
  30. Melbourne / 8
  31. Boston / 7
  32. Sydney / 6

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