Objectives To calculate individual cumulative mercury exposures from a convenience sample of dental professionals and measure the effect on peripheral nerve function.
Method Participants attended the American Dental Association’s (ADA) conventions held from 1997–2006. Individual surveys were completed and measurements were taken of the median and ulnar sensory nerve amplitude and latency in the dominant hand. The ADA has measured the average urinary mercury concentration of participants since 1977, allowing a cumulative mercury exposure to be estimated for each individual dentist based on the number of years they practiced dentistry. Both fixed and mixed effects (accounting for repeated measures) linear regression models were used.
Results 3923 observations from 2649 dentists were used to perform linear regression using multiple models. Models included individuals with or without imputed BMI, along with either repeated measures or initial observations only. Adjusted covariates included hand temperature, gender, age and BMI. Individuals with rheumatoid arthritis, diabetes, carpal tunnel syndrome (for median nerve models only), or hand temperatures interfering with the accuracy of the instrument were excluded. The main effect of cumulative exposure was found to be significant (p-value <0.05) in median nerve latency and amplitudes but insignificant in ulnar nerve measures. All models but ulnar nerve latency showed a highly significant interaction of cumulative exposure and age (p-value < 0.01).
Conclusions Using an estimated cumulative mercury exposure as the measure of effect shows a significant positive association with decreased peripheral nerve function. This study is the first of its kind to estimate dentists’ cumulative mercury exposure and its effect on peripheral nerve function.