A woman wears a face mask to protect her from polluted air in Lanzhou, China, in December．
A new study showed air pollution might put people more at risk for heart disease than scientists had thought．Kristin Miller, a doctoral student at the University of Washington, said chances of getting the disease were related to not only which city a woman lived in, but also where in the city．The study found that the effects of air pollution were often larger within cities than between cities．
The new findings make experts suspect that current pollution limits may be inadequate．Scientists examined rates of heart attack, stroke （中风） and other cardiovascular （心脏血管的） events in women with long-term exposure to air pollution．
The study involved women over the age of fifty who had no sign of cardiovascular disease at the start of the research．The study followed the women for as long as nine years to see how they would develop cardiovascular problems．
The researchers also examin
ed levels of fine particles （粒子，微粒） in the air in 36 areas across the country．That information came from the Environmental Protection Agency．The extremely small particles came from industrial smoke and traffic, along with things like wood-burning fireplaces in houses．
In the study, every ten-microgram increase in pollution was linked to a twenty-four percent increase in the risk of a cardiovascular event．But it was related to a seventy-six percent increase in the risk of death from cardiovascular disease．
But just how do particles in the air damage the cardiovascular system? The particles may cause the lungs to swell and release chemicals from the pollutants into the blood．The chemicals then could damage the heart．
1．The passage mainly talks about______．
A．the effects of pollution on women
B．how to protect women from air pollution
C．how air pollution damages a person’s heart
D．the 
relationship between air pollution and heart diseases
2．The case of the woman wearing a face mask shows ______．
A．people are paying more and more attention to their health
B．the woman is afraid of getting heart disease
C．Lanzhou city is more heavily polluted than other cities
D．air pollution is becoming more and more serious
3．We can learn from the passage that _______．
A．air pollution is more serious than scientists thought
B．the control of air pollution is effective in some cities
C．people throughout a city have the same risk of getting heart diseases
D．air pollution affects women more than men
4．The study implies that ______．
A．air pollution has a bigger effect on older women than younger women
B．small particles in the air mainly come from industrial smoke
C．the rise in air pollution may lead to a higher death rate from cardiovascular disease
D．air pollution has been affecting people for as long as nine years in the city of Lanzhou
