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第二部分：阅读判断
ADHD Linked to Air Pollutants
Children have an increased risk of attention problems，seen as early as grade school , if their moms inhaled(吸入)a certain type of air pollution when they were pregnant. That's the finding of a new study. Released when things aren't burned completely, this pollution is known as polycyclic aromatic hydrocarbons, or PAHs. The biggest sources of these PAHs: the burning of fossil fuels, wood and trash.
Frederica Perera works at Columbia University's Mailman School of Public Health in New York City. She researches how exposure to things in the environment affects children's health. In a new study , she and her team studied the exposure to air pollution of 233 nonsmoking pregnant women in New York City. Because burning tobacco can spew(排放) PAHs into the air and lungs, Perera's team focused on nonsmokers. The researchers wanted to probe(探查) other sources of PAHs, ones that would have been hard for an individual to avoid.
The team started by testing the blood of each woman during pregnancy. The reason: Any PAHs in a woman's blood would also be available to the baby in her womb. Nine years later, the researchers investigated signs of attention problems in these children, now age 9. They asked each child's mother a series of questions. These included whether her child had problems doing things that needed sustained(长期的) mental effort, such as homework or games with friends. The scientists also asked if the kids had trouble following instructions or made frequent, careless mistakes. All of these can be symptoms of a disorder called Attention Deficit Hyperactivity Disorder, or ADHD. About one in 10 U.S. children has ADHD.
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