Young children who are exposed to secondhand smoke have a much higher rate of tooth decay than children who do not grow up around smokers, according to a study supported by the Agency for Healthcare Research and Quality. The study is the first in the United States to associate secondhand, or passive, smoking with tooth decay?a public health problem that costs an estimated $4.5 billion annually. Although the occurrence of dental cavities in children has declined dramatically in the United States, little headway has been made in reducing cavities in children living in poverty, who generally have less access to dental care and appear to be more vulnerable to dental decay.