Scientists found that air pollution may be responsible     1     a significant reduction in intelligence. The research conducted by the World Health Organization ( WHO ) in China     2     (show) that air pollution led to big falls in test     3     (score) for languages and arithmetic. The study is called “The impact of exposure to air pollution on cognitive (认知的）performance ”. It was published in the Proceedings of the National Academy of Sciences journal. The study took place over four years. Researchers analyzed speaking and arithmetic tests taken by 20 000 people of all ages. They said， “Polluted air may prevent cognitive ability     4     people become older.”

The study is a warning to the rest of the world,     5     (especial) to those in cities. Over 91 percent of the world population live in areas with     6     (poison) air and air pollution is the     7     (four) highest cause of global deaths. Researchers discovered that     8     longer people were exposed to polluted air，the greater their intelligence went down. They said air pollution caused a year’s worth of lost education. For those     9     were over 60 years old，this could be several years. A researcher warned，“There is no shortcut     10     (solve) this issue. Governments really need to take effective measures to reduce air pollution.”