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The line graph shows the levels of two types of pollution, sulphur dioxide and smoke, in London from about 1585 to 2000. The levels are measured in micrograms per cubic metre.
Overall, both types of pollution increased for a long time and reached a peak in the 19th century, and then they fell sharply to almost zero in 2000. Sulphur dioxide was always higher than smoke.
At the beginning of the period, the level of sulphur dioxide was below 100 micrograms. It increased quickly to about 670 by 1690 and continued to rise with some changes. It reached the highest point of around 920 micrograms in about 1845. After 1890, it decreased, and from 1930 it dropped quickly to less than 50 in 2000.
Smoke followed a similar pattern, but the levels were lower. It started at about 30 micrograms and rose slowly to about 200 in the 1700s. Its highest level was about 440 in 1890. After that, the level of smoke decreased with many changes, and by 2000 it was close to zero.