Childhood Tooth Decay: Is It Linked to Lead?

Both epidemiologic and animal studies suggest that childhood lead exposure is associated with dental caries, or tooth decay, but proof based on human studies remains elusive. Although lead poisoning occurs in all socioeconomic groups, urban minorities are particularly affected because they frequently live in older housing, which often contains lead-based paint and lead-contaminated dust. This population also suffers a high incidence of tooth decay, causing some researchers to consider whether lead exposure could be a factor. In a study published this month, a team at the University of Rochester School of Medicine and Dentistry in New York explores the possibility of a link but does not find a definitive answer [EHP 108:1099-1102].

The team's objective was to see whether children with higher lead exposures at toddler age, when permanent teeth are developing, had more caries at school age than children with lower exposures. Headed by James R. Campbell of the Department of Pediatrics, the team drew on data collected by the Eastman Dental Center, which conducts a dental examination program for second- and fifth-graders in Rochester's public schools. Further data were provided by the Monroe County Health Department, which has maintained a database of blood lead concentrations in county children, including those in Rochester, since 1986.

By comparing data from both sources, the researchers identified a primary sample of 248 children who received dental examinations during the 1995-1996 and 1996-1997 school years and for whom information on blood lead concentrations at 18-37 months of age was available. Blood lead concentrations peak at about 2 years--up until that age, nearly everything a child touches goes into his mouth. The threshold for blood lead is established by the Centers for Disease Control and Prevention at 10 micrograms per deciliter ([micro]g/dL), and the Rochester team used this level to define low and high lead exposure in their study population.

Because tooth decay has several causes, the team attempted to control for confounding factors through interviews with the students' parents. Parental input provided information on demographics, fluoride exposure, diet, oral hygiene, and medical history for a secondary sample of 154 students. Keeping in mind three hypotheses regarding lead's involvement in tooth decay that suggest that deciduous (baby) and permanent teeth may be affected differently by lead, the researchers also noted which type of teeth were affected by decay.

Blood lead concentrations in the primary sample had ranged between 0 and 46 [micro]g/dL, with 34% of the children having had blood lead concentrations exceeding the defined threshold. In a simple comparison, 27% of the children with high blood lead concentrations had permanent tooth decay, as compared with 15% with low concentrations. Similarly, 59% of the children with high blood lead concentrations had deciduous tooth decay, compared with 46% with low concentrations. However, the children with high blood lead concentrations were older and had more permanent tooth surfaces--not only had they had more time to develop caries in permanent teeth, they simply had had more time to get permanent teeth. When these variables were included alongside information supplied by parents in more sophisticated statistical analyses, no valid, significant association was found.

Based on these analyses, the researchers conclude that tooth decay is not strongly linked to lead exposure, but they cannot rule out that a weak association exists. The authors also speculate that the difference between the two groups may not be significant because none of the children are so old as to see much permanent tooth decay. Significance might be better determined when these children are older.