According to the World Health Organization, air pollution kills about________around the world each year.

Air pollution is a killer. The World Health Organization says it kills an estimated seven million people around the world each year. Even if polluted air does not kill us, it can make us very sick. However, breathing dirty air may do more than hurt your body. It can also affect your brain and your ability to think.
   A new study shows that air pollution can cause a "huge" reduction in our intelligence. The study was a project involving researchers at Peking University in China and Yale University in the United States. The researchers reported that long-term exposure to air pollution can affect a person’s mental abilities in two areas: language and mathematics.
   The researchers studied about 25, 000 people from across China. Between 2010 and 2014, these Chinese men, women and children were given language and math tests. Then researchers compared the test results with measurements of pollution in the air, namely nitrogen dioxide and sulfur dioxide.
   Xi Chen of the Yale School of Public Health led the study. He and his team found that breathing polluted air can reduce a person’s education level by about one year. Chen said that the effect generally is worse for those over 64 years of age, for men and for those with little or no education. "The older persons — they are more affected. And we find, quite interestingly, males are more affected than females. And people working outdoors are more affected than people working indoors. "
   The researchers noted that the effect of pollution on verbal ability is even more serious as people age, especially among men and the less educated.
   In May 2018, the WHO reported that nine of every 10 people worldwide are breathing polluted air. The study we described earlier found that people who work outdoors fall into a high-risk group. However, that does not mean those who work inside buildings are safe from air pollution.