The bar chart illustrates peak and minimum levels of Sulphur dioxide (502) and Dinitrous oxide (NO2), two air pollutants, in four cities, namely Los Angeles, Calcutta, Beijing and Mexico, in 2000. The figures are measured in micrograms per cubic metre. Overall, the average presence of these two air polluting ingredients is much higher in Mexico than in the other three cities. To begin with, the minimum level of SO2 in Los Angeles amounted to 1 microgram per cubic meter, nine micrograms less than its maximum level. The difference was increased in both levels in Calcutta, accounting for 47 micrograms and 59 micrograms per cubic meter, respectively. The minimum level of pollution in Mexico generated by SO2 was 55 micrograms more than the level of SO2 in Beijing, but the maximum range went as high as 130 in Beijing, and The presence of this air pollutant reached 200 in Mexico. Furthermore, with N20, the second air polluting material, Dinitrous oxide, on average, found more in Mexico. The minimum level of N20 in Mexico was more than 110, which was almost ten times higher than that of Beijing and approximately 75 micrograms per cubic meter more elevated than that of Calcutta and Los Angeles. The upper level of N20 in Los Angeles was higher than N20 in Calcutta and Beijing, but it was about half of the N20 level in Mexico.