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The chart shows air pollution levels by different causes among four countries in 2021.

The bar chart compares the levels of air pollution caused by electricity generation, transport and industry among four nations, namely China, America, Japan and Australia in the year 2021. Units are measured in parts per million (ppm).

Overall, air pollution in the four countries mostly resulted from transport and industrial sectors. Chinese suffered from by far the most serious problem, while the air quality in Australia was relatively acceptable.

Polluted air from industrial activities in China recorded the highest value of 80 ppm, followed by transport and electricity generation, at around 70 and 60 ppm respectively. By contrast, all data for Australia stood at merely 29 ppm each, at least three times as low as those in China.

Emissions from transport and electricity generation in America was in the second place among the four countries (roughly 58 ppm and 31 ppm respectively), almost doubling those of Japan. Meanwhile, the Japanese industrial sector contributed the most to air pollution in this country, with a level of about 42 ppm, compared to just below 30 ppm in America.