The line graph illustrates the changing pattern of pollution levels in London from 1600 to 2000, measured in micrograms per cubic meter.
Overall, there were significant shifts in pollution levels of sulphur dioxide and smoke over this 400-year period. Both pollutants started at similar levels below 250 micrograms per cubic meter around 1600. The level of sulphur dioxide rose gradually between 1650 and 1700, peaking at over 750 micrograms per cubic meter between 1700 and 1750. It remained at a high level until about 1900, with a slight decline between 1750 and 1800. After 1900, sulphur dioxide levels dropped dramatically, reaching near zero by 2000.
In comparison, smoke pollution, initially lower than sulphur dioxide, increased steadily from 1600 to 1800, reaching about 250 micrograms per cubic meter. It peaked at almost 500 micrograms per cubic meter between 1850 and 1900. However, there was a sharp decline in smoke pollution after 1900, plummeting to zero by 2000.
In summary, while both sulphur dioxide and smoke pollution levels increased significantly from 1600 to 1900, there was a marked decline in both pollutants in the 20th century, with levels reaching near zero by 2000.