Cities in Iran, India, Pakistan and the capital of Mongolia rank among the worst on the planet for air pollution, while those in the US and Canada are among the best, according to the first global survey by the WHO.
The southwest Iranian city of Ahvaz walked away with the unfortunate distinction of having the highest measured level of airborne particles smaller than 10 micrometers.
The WHO released the list on Monday to highlight the need to reduce outdoor air pollution, which is estimated to cause 1.34 million premature deaths each year. The global body said investments to lower pollution levels quickly pay off because of lower disease rates and, therefore, lower healthcare costs.
The list, which relies on country-reported data over the past several years, measures the levels of airborne particles smaller than 10 micrometers — so-called PM10s — for almost 1,100 cities.
The WHO recommends an upper limit of 20 micrograms for PM10s, which can cause serious -respiratory problems in humans. They are mostly sulfur dioxide and nitrogen dioxide from power plants, auto exhausts and industry.
Ahvaz’s annual average of PM10s was 372 micrograms per cubic meter. Heavy industry and low-quality vehicle fuel are the main causes of air pollution in the desert city of 1.3 million.
The study found that the Mongolian capital Ulan Bator had an annual average PM10s density of 279 micrograms per cubic meter, followed by another west Iranian city, Sanandaj, with 254 micrograms.
Cities in Pakistan and India, such as Quetta and Kanpur, as well as Botswana’s capital Gaborone, also ranked high on the pollution scale.
Mohammed Hasan, 39, of Karachi, Pakistan, said attempts to improve air quality in the port city of 18 million — such as by replacing heavily polluting buses with vehicles using compressed natural gas — are being undermined by bigger polluters who are “playing havoc with the lives of Karachi populace.”
“Industries and factories are emitting thick clouds of smoke and no government agency is out there to check them or correct them,” the bank employee said.
The WHO said the reasons for high pollution levels varied, but that often rapid industrialization and the use of poor quality fuels for transportation and electricity generation are to blame.
In India, major metropolitan areas such as New Delhi, Mumbai and Kolkata have banned the construction of new power plants within city limits and existing ones are being shut down or relocated.
However, at the same time, a lack of public transport has led to an explosion of privately owned cars and SUVs as the economy booms, with the number of heavily polluting diesel vehicles increasing 10-fold as diesel is highly subsidized by the government.
In Ulan Bator, the air pollution is mainly related to the burning of coal, wood and everything else for heating, cooking and electricity generation. Coal-fired power plants spew smoke over the city, which lies in a valley surrounded by mountains that trap and hold the pollution, much like Beijing.