Diagnostic Chelation Challenge with DMSA: A Biomarker of Long-Term Mercury Exposure?

Abstract

ArticlesChelation challenge testing has been used to assess the body burden of various metals. The bestknown example is EDTA challenge in lead-exposed individuals. This study assessed diagnostic chelation challenge with dimercaptosuccinic acid (DMSA) as a measure of mercury body burden among mercury-exposed workers. Former employees at a chloralkali plant, for whom detailed exposure histories were available (n = 119), and unexposed controls (n = 101) completed 24-hr urine collections before and after the administration of two doses of DMSA, 10 mg/kg. The urinary response to DMSA was measured as both the absolute change and the relative change in mercury excretion. The average 24-hr mercury excretion was 4.3 µg/24 hr before chelation, and 7.8 µg/24 hr after chelation. There was no association between past occupational mercury exposure and the urinary excretion of mercury either before or after DMSA administration. There was also no association between urinary mercury excretion and the number of dental amalgam surfaces, in contrast to recent published results. We believe the most likely reason that DMSA chelation challenge failed to reflect past mercury exposure was the elapsed time (several years) since the exposure had ended. These results provide normative values for urinary mercury excretion both before and after DMSA challenge, and suggest that DMSA chelation challenge is not useful as a biomarker of past mercury exposure. EHP puts even more environmental health information right at your fingertips!EHP online articles contain convenient l li in nk ks s t to o P Pu ub bM Me ed d-the National Library of Medicine's free online search service of more than 9 million citations! Search MEDLINE and Pre-MEDLINE (including links to other online journals and databases) for information directly related to each EHP article's topic! Subscribe to EHP today at http://ehis.niehs.nih.gov/

Overview of the clinical toxicity of mercury

“…However, this is not always reliable as shown by the lack of di¡erence in response to DMSA between previously exposed workers and con-trols. 119 When chelation increases excretion, there is a problem with interpretation and the problem is increased when there is no baseline value and mercury is estimated only once. 120 The following example illustrates the di⁄culties.…”

ACMT Recommends Against Use of Post-Chelator Challenge Urinary Metal Testing

“…Chelating agents such as dimercaptosuccinic acid (DMSA), dimercaptopropanesulfonic acid (DMPS), dimercaptol (BAL), and edetate calcium disodium (CaNa2-EDTA) bind metallic and metalloid elements and increase their urinary elimination from both healthy and metalintoxicated individuals [4,[7][8][9][10]. However, scientifically acceptable normal reference values for post-challenge urine metal testing have not been established [4,5,9,11,12]. The results of post-chelator urinary metal testing cannot be compared to normal reference values [5,11].…”

Kelatordiagnostikk og amalgamfyllinger

“…Det er vist at verdiene etter kelatortest i stor grad kan forutsis av den uprovoserte kvikksølvverdien i urin og mengden amalgam i tennene (amalgamflater) (4). Det er også tvilsomt om kelatorer kan belyse tidligere kvikksølveksponering (5).…”