Unclean air is believed to______(2 words) nearly one third of the years of healthy life....

Scientists say that air pollution causes more harm to the lungs, heart and brain than was estimated. Air pollution has become a major contributor to stroke for the first time. Unclean air is believed to account for nearly one third of the years of healthy life lost to the condition worldwide.
   In a survey of global risk factors for strokes, air pollution in the form of PM2.5 ranked seventh in terms of its impact on healthy lifespan, while household air pollution from burning solid fuels ranked eighth. About 15 million people a year suffer from a stroke worldwide. Nearly six million die, and five million are left with permanent disabilities, such as loss of sight and speech.
   The most important contributors to stroke worldwide included high blood pressure, a diet low in fruit, obesity, a high salt diet, smoking, and not eating enough vegetables. Nearly three quarters of the global burden of stroke was linked to lifestyle choices, such as smoking, bad diet and inactivity, suggesting that people can do a lot to reduce their risk of stroke. There is increasing evidence that air pollution has severe adverse toxic effects in multiple parts of the body from conception to old age.
   As one of the main sources of air pollution is car emissions, staying away from the streets, especially at rush hour, or avoiding busy roads, can help reduce exposure to air pollution. On days when air pollution is high, people should stay indoors as much as possible.