• Breathing polluted air puts you at a higher risk for asthma and other respiratory diseases.
• When exposed to ground ozone for 6 to 7 hours, scientific evidence show that healthy people’s lung function decreased and they suffered from respiratory inflammation.
• Air pollutants are mostly carcinogens and living in a polluted area can put people at risk of Cancer.
• Coughing and wheezing are common symptoms observed on city folks.
• Damages the immune system, endocrine and reproductive systems.
• High levels of particle pollution have been associated with higher incidents of heart problems.
• The burning of fossil fuels and the release of carbon dioxide in the atmosphere are causing the Earth to become warmer.
• The toxic chemicals released into the air settle into plants and water sources. Animals eat the contaminated plants and drink the water. The poison then travels up the food chain – to us.

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  Hydrocarbons (HC). These pollutants react with nitrogen oxides in the presence of sunlight to form ground level ozone, a primary ingredient in smog. Though beneficial in the upper atmosphere, at the ground level this gas irritates the respiratory system, causing coughing, choking, and reduced lung capacity.
  
  

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  Nitrogen oxides (NOx). These pollutants cause lung irritation and weaken the body's defenses against respiratory infections such as pneumonia and influenza. In addition, they assist in the formation of ground level ozone and particulate matter.
  
  

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  Carbon monoxide (CO). This odorless, colorless, and poisonous gas is formed by the combustion of fossil fuels such as gasoline and is emitted primarily from cars and trucks. When inhaled, CO blocks oxygen from the brain, heart, and other vital organs. Fetuses, newborn children, and people with chronic illnesses are especially susceptible to the effects of CO.
  
  

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  Sulfur dioxide (SO2). Power plants and motor vehicles create this pollutant by burning sulfur-containing fuels, especially diesel. Sulfur dioxide can react in the atmosphere to form fine particles and poses the largest health risk to young children and asthmatics.
  
  

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  Hazardous air pollutants (toxics). These chemical compounds have been linked to birth defects, cancer, and other serious illnesses. The Environmental Protection Agency estimates that the air toxics emitted from cars and trucks — which include Benzene, acetaldehyde, and 1,3-butadiene — account for half of all cancers caused by air pollution.
  
  

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  Greenhouse gases. Motor vehicles also emit pollutants, such as carbon dioxide, that contribute to global climate change. In fact, cars and trucks account for over one-fifth of the United States' total global warming pollution; transportation, which includes freight, trains, and airplanes, accounts for around thirty percent of all heat-trapping gas emissions.

2. Gwalior, India

3. Allahabad, India

4. Riyadh, Saudi Arabia

5. Al Jubail, Saudi Arabia

6. Patna, India

7. Raipur, India

8. Bamenda, Cameroon

9. Xingtai, China

10. Baoding, China

11. Delhi, India

13. Dammam, Saudi Arabia

14. Shijiazhuang, China

15. Kanpur, India