A United Nations report released this month showed that the vast majority of the world's population - as many as 6.76 billion people - live in areas where air pollution exceeds recommended levels. This is 92% of the entire human race. But understanding the nature of air pollution (pun intended) is more complicated than it seems. The World Health Organization's measurements may seem dizzying, and the fact that it's often smaller places rather than metropolitan areas that top the list of the world's most polluted cities can be, frankly, confusing. But there's a good reason we need to understand these numbers: air pollution is highly deadly. The United Nations estimates that about 6.5 million people die each year from air pollution-related illnesses, and a March study found that the economic cost of pollution in the United States alone is about $4.3 billion annually. This is neither a cheap nor an inconsequential question. So what do these numbers say?
The main source of air pollutant measurements is the World Health Organization, which publishes an annual report on the state of the world's air health. They're not just collecting numbers, either. In May this year they set out a "roadmap" to reduce global pollution levels, and new data for 2016 includes information from more than 3,000 locations around the world. (That's still not enough in some places, as we'll get to in a moment.) But measuring air pollution levels isn't as easy as going out, smelling the air, coughing, and moving to another country. The World Health Organization uses two different measures of air pollution: "fine" particles of 2.5 microns or smaller (which is about 1/30 the width of a human hair, The Washington Post explains), and 2.5 to 10 microns. of “respirable coarse particles”. Micron. These are not the only types of air pollution in the world, but they appear to be the most harmful to human health. Different processes produce what scientists call PM2.5 and PM10, each with different effects on humans.
PM2.5 particles are the worst for respiratory health. When we inhale them, their tiny size means they can carry toxic pollutants into the lungs, which, according to the latest scientific review from January 2016, "can cause asthma, airway inflammation, harm lung function, and even promote cancer." PM2 .5 An increase in daily concentrations of just 10 micrograms per square meter increases respiratory disease incidence by more than 2%, hospitalization rates by 8%, and overall mortality by 0.2-0.6%. PM10s are considered slightly less dangerous, but inhaling them is still linked to respiratory problems, asthma exacerbations, and lung and cardiovascular problems.
The World Health Organization lists sources of PM2.5 and PM10 around the world, and they are quite diverse: internal combustion engines, coal, oil and other heavy fuels, construction, cement and brick manufacturing, road erosion, traffic, urban dust air, and many more something else. Yes, airborne dust and soil are effective pollutants.
Cities with the worst particulate matter pollution
The new model launched by the World Health Organization includes a view of the entire world map of PM2.5 levels, and it's not a pretty sight. While most of North America is within acceptable levels, much of Africa, China, India and Saudi Arabia are a dazzling purple, indicating levels of PM2.5 pollution in the air far exceed the World Health Organization's Recommended level. (You can look up your own city if you want.)
But when it comes to global PM2.5 levels, the winner (if you can call it that) in terms of particulate matter levels is the Iranian city of Zabor. Never heard of it? This is not surprising. But you might be surprised to learn that it's not an industrial center or some notorious coal-burning site. Zabor's air pollutant levels were caused by unprecedented dust storms, which became more severe after nearby wetlands dried up in 2000, the Guardian reported. There can be continuous sandstorms here for up to 120 days each year - a veritable crisis. Suffocating the city.
The Indian media was surprised and delighted by the rest of the WHO list, with most Indian cities making it into the top ten for one reason: Delhi, often called the most polluted place in India, was beaten by four other Indian cities . (Delhi’s PM2.5 levels have dropped to 122 after being rated 153 by the World Health Organization in 2014, leading to an overall improvement in Delhi’s air quality. To demonstrate how bad the situation still is, the World Health Organization’s ideal The annual average PM2.5 level is 10.) Gwalior city in Madhya Pradesh ranks second after Zabor, followed by the Indian metropolises of Allahabad, Patna and Raipur. Rounding out the top ten are the Cameroonian cities of Bamenda and Xingtai, which has been China's most polluted city for years due to its steel mills and coal-fired power plants. (It beat out Baoding, also in Hebei Province, known as China's "ground zero" for air pollution.)
In the United States, the worst PM2.5 levels are not necessarily found in large cities. The American Lung Association, which collected data on PM2.5 levels across the United States, ranked Bakersfield, California, as the most polluted state, followed by Fresno, San Jose, Los Angeles and San Francisco. California may appear to be a healthy state, but it really doesn't do much for its citizens' lungs.
Cities with the worst gross air pollutants
In terms of PM10 pollution, Zabor ranks third, behind two other cities: Onitsha in Nigeria and Peshawar in Pakistan. Onitsha is at the center of a national problem - CNN reports on a World Bank statistic that 94% of Nigeria has air pollution levels that exceed World Health Organization guidelines. Apparently the reason for the region's PM10 levels is often a reliance on fuel, dirty generators and emissions-producing cars. This is a hard combination to fix.
When the World Economic Forum looked at PM10 pollution levels, it highlighted something unique about all the cities in the top 20 (from Iran to India to Afghanistan, with just one entry from China): They are located in economically similar regions. These "fast-growing economies," as the World Economic Forum calls them, tend to use large amounts of resources quickly as more people move there to work, and still rely on older equipment such as wood burning and diesel. result? The air is really bad.
If you're less interested in smaller places and more interested in larger cities, PM10 data suggests Delhi and Cairo are your worst options, followed by Dhaka, Kolkata, Mumbai and Beijing in Bangladesh. (Some of the best, according to the World Health Organization, are Wellington, Toronto, Madrid, Sydney and London in New Zealand.) In the United States, the two worst cities for large PM10 levels are Los Angeles and New York, but their urban levels Still low, at 20 and 16 respectively. By comparison, Delhi ranks 229th.
But there are limits. WHO noted that there is a severe shortage of monitoring stations in Africa, Eastern Europe and Russia, and that more monitoring stations would allow us to gain a more accurate understanding of global air pollutants. Hopefully more cities will follow Delhi’s lead. Humiliated by its previous poor rating from the World Health Organization, it made systemic changes and appears to have weakened its PM levels, even though its rating remains low.
