NEET BIOLOGY

Detailed explanation-1: -The pollution was the result of decades of industrialization that began in the 1940’s. In that time, Mexico City had become home to millions of vehicles without pollution controls, running on toxin-and pollutant-laden fuel, as well as highly polluting oil refineries, power plants and factories.

Detailed explanation-2: -Located in the crater of an extinct volcano, Mexico City is about 2, 240 metres above sea level. The lower atmospheric oxygen levels at this altitude cause incomplete fuel combustion in engines and higher emissions of carbon monoxide and other compounds. Intense sunlight turns these into higher than normal smog levels.

Detailed explanation-3: -It earned the accolade of the world’s most polluted city. A management programme was introduced which introduced reforms that would clean up the air. Levels of ozone were reported to be around 500 parts per billion (ppb), they are now at a more respectable level of between 120 and 150 ppb.

Detailed explanation-4: -This was partly due to Mexico City’s high altitude (7382 ft above sea level), which causes its oxygen levels to be 25% lower. Carbon-based fuels also do not combust completely. Other factors include the proliferation of vehicles, rapid industrial growth, and the population boom.