Serum Neuron-Specific Enolase in Lead-Exposed Individuals.

The article by Ravibabu, et al, 1 provides important new data in the field of biomarkers to monitor exposures to lead within the workplace, as in the lead acid battery manufacturing. They found that the serum neuron-specific enolase (NSE) levels are not elevated in association with concentrations of blood lead levels among workers in the lead acid battery manufacturing plant. In our (unpublished) cases we also found that serum NSE levels did not correlate with changes in lead concentrations in whole blood among individuals with potential exposure to lead. However, we would like to clarify some of the issues raised by Ravibabu and colleagues. In the introduction section, they state that “the levels of serum NSE were associated with exposure to solvents, chromium, 1-bromopropane, 2,5-hexanedione...” However, if we are correct, serum NSE levels is likely to be a more effective biomarker for mercury toxicity than chemical substances that the authors cite (ie, solvents, chromium, 1-bromopropane, 2,5-hexanedione). The authors acknowledge this point in their Discussion of the clinical evaluation of serum NSE levels as a marker of traumatic brain injury, silicosis, mercury intoxication, pneumoconiosis, and in chromium-exposed as well as carbon monoxide-exposed persons. We were surprised, however, that there is no mention in their Introduction, or in the Discussion section, of the role of serum NSE as a biomarker of effects associated with mercury poisoning that was first reported and suggested by Benz, et al. We argue that the case study by Benz, et al, was the first to evaluate the potential association between mercury poisoning and serum NSE levels in humans. And our report on four patients with mercury overexposure, subsequently published, shows that there is an association between mercury exposure and levels of serum NSE, which is a good indicator of alterations in the central as well as the peripheral nervous system cellular structure and biochemical processes. Serum NSE seems to be a promising biomarker of effects for mercury exposure in humans. Future studies evaluating the effects of mercury exposure on serum NSE are needed.