Environmental lead exposure appears to increase the risk of cavities in children, adolescents and adults in the United States, according to findings published in the June 23 issue of the Journal of the American Medical Association (JAMA). Researchers at the University of Rochester, together with colleagues at Children's Hospital Medical Center of Cincinnati, estimate that about 11 percent of the tooth decay seen in children today may be due to moderate or high levels of lead exposure.
"Some 2.7 million children between the ages of 5 and 17 may have increased susceptibility to tooth decay because of lead exposure," says Mark E. Moss, D.D.S, Ph.D., of the University of Rochester School of Medicine and Dentistry and the study's lead author. Moss, a researcher in the University's Eastman Department of Dentistry, conducted the study with Bruce P. Lanphear, M.D., M.P.H., associate professor of pediatrics at Children's Hospital Medical Center of Cincinnati, and Peggy Auinger, a data analyst at Children's Hospital at Strong Memorial Hospital and at Rochester General Hospital.
The team made the finding by combing through data collected on nearly 25,000 individuals, ages two and older, who participated in the Third National Health and Nutrition Examination Survey. The survey was conducted from 1988 to 1994 by the National Center for Health Statistics to assess the health and nutritional status of children and adults in the United States. Moss and Lanphear found that even after adjusting for diet, dental care, and other social and demographic factors, an increased amount of lead in the blood meant an increased risk of tooth decay. The finding proved true for all age groups and for both baby and permanent teeth.
In the study funded by the National Institutes of Health, Moss and Lanphear found that in children each increase in blood levels of lead of 5 micrograms per deciliter boosted risk of tooth decay 80 percent.
"Lead is a systemic toxin that affects virtually every organ system, even at levels previously thought to be low," says Lanphear. "This study helps to explain the disproportionately high rate of cavities among inner-city children. Despite the decline in children's blood lead levels, lead exposure remains a major public health problem that persists throughout adulthood and entails major medical and dental costs to the U.S. population."
Lead is well recognized as causing developmental and other problems. While lead has been removed from most gasoline, it's still present in old paint and commonly in soil or dust around contaminated buildings, as well as in some window blinds and glazes on some pottery. In their paper, Moss and Lanphear note that the region of the United States with the highest lead pollution—the Northeast—is also where dentists see the highest rates of tooth decay.
The results reinforce the announcement two years ago by another University of Rochester team that while lead does not actually cause cavities, it appears to make rats— and thus people, whose teeth get cavities in an identical manner—much more susceptible. Those researchers found that offspring of rats exposed to lead had 40 percent more cavities than rats whose mothers were not exposed.
Lead is likely one reason why dental cavities are still a major problem in some pockets of the population despite the widespread use of fluoride and fluoridated toothpaste, says dental researcher William Bowen, D.D.S., D. Sc., who conducted the 1997 study and is the founder of the Rochester Caries Research Center, the nation's first research center on tooth decay. By age 17, 84 percent of children have tooth decay, and 95 percent of all adults in the U.S. have cavities, which are a leading cause of tooth loss. Annual treatment cost for cavities and their consequences, which are a major cause of sick days in the work place, is estimated to be anywhere from $4.5 billion to $20 billion.
Just how lead may interfere with the development of teeth is the subject of ongoing studies at Rochester. In humans, lead is stored in the bones for decades, and high amounts are released into the blood of women who are pregnant. These high levels reach the fetus at a time critical to the development of teeth and salivary glands.
"Dentists think that some children have poor dental habits when in fact, they may be brushing and flossing regularly, are exposed to fluoride treatments, and have regular dental check-ups. Lead may be a factor in such cases," says Moss, who is an epidemiologist and assistant professor in the Department of Community and Preventive Medicine.
"If a causal association between environmental lead exposure and cavities is substantiated, it would have important implications concerning the need to broaden the focus of dental health interventions beyond modifying dietary habits, improving personal oral hygiene, and increasing fluoride exposure. This research provides an additional compelling reason for an effective program of removing lead from our environment," he adds.