Children in poor, predominantly minority neighborhoods in New York City are as much as 21 times more likely than children from affluent parts of the city to be hospitalized for asthma, according to a new study. Doctors suspect that a number of environmental factors contribute to the nation’s urban asthma epidemic, including indoor and outdoor pollutants, pesticides, auto emissions, and dirt and dust in the air. Acute asthma attacks among children have increased 100 percent in the last decade, and asthma is now the most common cause of hospitalization among American children.