The given graph illustrates various sources of air pollutants in the UK from 1990 to 2005. Overall, it is evident that the level of total air pollutants decreased significantly throughout the period.
To begin with, in 1990, the volume of emissions produced by households and transport was the same, at 1 million tonnes. Meanwhile, the industrial sector emitted approximately 6 million tonnes, making it the largest contributor at the start. Emissions from this source then sharply declined to 3 million tonnes within six years, and gradually decreased towards the end of the period.
Moreover, the level of air pollution generated by households fluctuated slightly, before finishing the period at 0.2 million tonnes. In contrast, air pollution from transport showed a gradual upward trend and peaked at 1.3 million tonnes in 2002, before ending slightly lower at just above 1 million tonnes in 2005 — over five times higher than that of households.
As a result, the total air pollutants steadily fell throughout the period, ending at nearly 3 million tonnes — less than half of the initial amount.