The graph below shows the daily average minimum and maximumlevels of air pollutants in four big cities in 2000. v.2

The bar graph gives information about the average lowest and highest amount of SO2 and N2O in four separate regions in 2000. Overall, Los Angeles and Mexico city have more N20 than S02 while Calculta and Beijing have opposite trend. As can be seen from the chart, the maximum level of SO2 and N20 in Mexico city were 200 and 207 micrograms per m3 respectively, which doubled the minium around 80 to 100 micrograms per m3. Los Angeles was mainly contaminated by N20 with the lowest and highest figures being 39 and 104 micrograms per m3 appropriately, while the maximum amount of S02 was only 10 micrograms per m3. The second most polluted city was Beijing where had a minimum of 25 micrograms per m3 and a maximum of 130 micrograms per m3 of S02, whereas the amount of N20 fluctuated from 14 to 54 micrograms per m3. The level of air pollution was shown by correspondingly 47 to 59 micrograms per m3 of S02 and 30 to 52 micrograms per m3 of the other air pollutant.