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When you think about health, air quality might not be the first thought that runs through your mind. However, this often-overlooked factor is very important when it comes to long term health. According to the World Health Organisation (WHO), there is a positive correlation between exposure to excessive amounts of air pollution and mortality and morbidity.

The type of air pollution also matters. High concentrations of PM2.5 and PM₁₀ specifically place individuals at risk of cardiovascular diseases such as strokes, heart disease, respiratory infections, pulmonary diseases and lung cancer. PM is short for ‘particulate matter’. PM usually contains a mixture of solids and liquids including sulfate, ammonia, nitrates, sodium chloride, black carbon, mineral dust and water. PM₁₀ consists of particles with a diameter of 10 microns or less, while PM2.5 consists of particles with a diameter of 2.5 microns or less. These minute particles can penetrate deep into the lungs (and PM2.5 can even cross the lung barrier and enter the bloodstream, which is even more damaging to human health).

In a quest to find out which cities’ residents are most at risk of poor health due to air pollution, we consulted the 2018 edition of the WHO Global Ambient Air Quality Database. This database consolidates annual mean PM2.5 and PM₁₀ measurements for over 2600 cities and towns across the globe. The results were astonishing, with each of the top 10 cities coming in well over the recommended upper limit of 10 μg/m3 for PM2.5.

The WHO guidelines for safe/acceptable  annual mean PM measurements are as follows:

  • Fine particulate matter (PM2.5): 10 μg/m3
  • Coarse particulate matter (PM₁₀): 20 μg/m3

Here are the top 10 cities with the worst air quality as measured by their PM2.5  concentrations:

  1. Kanpur, India: 173 μg/m3

Kanpur is the 12th most populous city in India. It is  home to Kanpur Central, one of the busiest railways in the country, with approximately 300 trains passing through daily. 4 major highways run through Kanpur, and the Kanpur airport services local travellers for flights to Delhi, Mumbai, and Kolkata. Apart from transport services, cars, and factories, Kanpur also has a booming leather industry that makes use of harsh chemicals that contribute to pollution.

  1. Faridabad, India: 172 μg/m3

Faridabad is situated in the state of Haryana, and is one of India’s leading industrial centres. It is Haryana’s most populous city and is famous for its henna industry. There are also numerous other manufacturing industries that thrive in Faridabad, including the tractor, refrigerator, tyre, apparel, refrigerator, and motorcycle industries.

  1. Gaya, India: 149 μg/m3

Gaya is situated in the state of Bihar, and is a well-known religious tourist centre for Jainism, Buddhism, and Hinduism. Agriculture is Gaya’s leading economical driver, and the city also has a number of home industries that produce goods such as incense, confectionery, woven textiles and garments, and stone items. There are also small metal, machinery, and equipment industries in the city.

  1. Varanasi, India: 146 μg/m3

Varanasi plays a significant role in Hinduism, as it is considered the holiest of the seven sacred Hindu cities. It is also said that Buddha founded Buddhism in Varanasi. The city forms part of the state of Uttar Pradesh, and is a prominent industrial centre that specialises in the production of muslin, silk, metal products, perfume, and ivory goods.

  1. Patna, India: 144 μg/m3

Patna is the capital of Birha, and ranks as the 21st fastest growing city in India according to the City Mayor’s Statistics report. It is East India’s second largest city and exports a number of agricultural products including sugarcane, rice, and sesame seeds. Patna also has several major railways and four national highways running through it.

  1. Delhi, India: 143 μg/m3

With the second highest population in India, it is easy to see why Delhi has also become northern India’s largest commercial centre. Delhi also has the highest road density in India (2103km/100km²), with a total of 1,05,67,712 registered vehicles on the road in 2017. These vehicles include cars, motorcycles, scooters, cabs, three-wheelers, cabs, and busses, rickshaws, and maxi cabs.

  1. Lucknow, India: 138 μg/m3

Lucknow is the capital city of Uttar Pradesh, and the 11th most populous city in India. Key industries include automotives, furniture, aeronautics, machine tools, embroidery, and chemicals. In 2010, Lucknow was voted the 6th fastest job-creating city in India.

  1. Bamenda, Cameroon: 132 μg/m3

The only non-Indian city on our list, Bamenda is a prominent African city with a population of approximately 2 million. Agriculture (specifically coffee) is the city’s main trade, and it also has prominent food processing, construction, crafts, and tourism and hospitality industries. Interestingly, Bamenda’s poor air quality is due to deforestation and climate change as opposed to factory and transport emissions.

  1. Agra, India (131 μg/m3)

Agra is located in the state of Uttar Pradesh, and is ranked the 23rd most populous city in India. Agra is home to the famous Taj Mahal, which contributes to its bustling tourist industry. Agriculture, footwear, leather, and iron are also major sources of income for Agra’s residents.

  1. Gurgaon, India: 120 μg/m3

Gurgaon is located in the state of Haryana, and is home to the Indian offices of 250 Fortune 500 companies. Maruti Suzuki Pty Ltd set up a car manufacturing unit in Gurgaon in the 1970s, and in 1997 General Electric was the first major American company to set up a manufacturing plant in the city.