Asthma is a serious medical condition because it is lifelong; there is no cure. A study says that pollution from traffic connects to 4 million new cases of asthma in children each year.

Researchers studied the pollution and how it affects children¡¯s health in 194 countries and 125 large cities.

This is not the first study to make this claim, but the study¡¯s main author says that it gives a comprehensive idea of the problem. She says that it tells where pollution ¡®hot spots¡¯ are.

Some people think that worldwide rules for pollution need to change. Another idea is to make it easier to have cleaner transportation.

The author also said that there are other pollutants in the world causing diseases, such as lung cancer, strokes, heart disease, and developmental issues.

Difficult words: pollution (smoke which comes from cars, planes and ships), comprehensive(broad, big), developmental (how the body develops/grows).