The given line chart shows the gradual decrease in air pollution levels from industries, households and transport over the period from 1990 to 2005. More specifically, emissions from transport remained relatively stable in the early years before sharply increasing after 1999.
As shown in the chart, the total emissions saw a gradual decline, starting at around 8 million tons in 1990 and falling by about 3 million tons by the end of the period. Similarly, the industrial emissions experienced a considerable fall during the same period, standing at nearly 6 million tons in 1990 before dropping to around 2 million tons after the 15-year period.
Also, pollution from household activities underwent a slight decrease, from 1 million tons to almost zero, making it the least significant source of pollution in the list. In contrast, the transport emissions saw a sharp increase in 1999 after a long period of maintaining a low level, remaining marginally between 1 and 1.5 million from 1990 to 1999. After 1999, it remarkably climbed to 2 and 3 million tons in 2002 and 2005, respectively.
Overall, the data indicate that households were the least polluting factor during the period mentioned, while the level of pollution caused by all sources combined remained the highest, despite its downward trend.