Evaluation of Sorbents in Managing Hg Vapor from Amalgam Waste

Objective: This study assessed the capacity of carbon-based mercury (Hg) vapor binding material (sorbents) to limit Hg vapor released from stored dental amalgam waste. Methods: Four different sorbents were evaluated: Activated carbon (AC), AC impregnated with sulfur (GC-IPSp), AC mixed in the lab with sublimed iodine (AC-SI), and AC impregnated with iodine crystals (GC-II). Ten grams of ground and sieved amalgam (210-710µm) were placed into forty tightly-sealed HDPE containers: 200 grams of sorbent were put into mesh bags then placed inside thirty-two containers (an additional eight containers had no sorbents). Hg vapor measurements were made with either of two instruments (depending on vapor level): OhioLumex RA-915+ Hg vapor analyzer (baseline and treatment samples) or Arizona Instruments Jerome 431X (control samples). Containers were sampled in random order with measurements taken Tuesday through Friday at 7AM for four weeks. Baseline Hg vapor levels were determined for each container prior to placement of amalgam. Results: The table shows weekly means in nanograms of Hg per cubic meter of air.  Over four weeks, Hg vapor levels generally decreased (presumably due to surface oxide formation) and differences between groups diminished.  Mean removal efficiencies at Week 1 were calculated to be 99.97%, 99.98%, 99.99% and 99.99% for AC, GC-IPSp, AC-SI, and GC-II, respectively. Control data was not included in any analysis. A 2-way ANOVA (group by week) had significant main effects and interaction. 1-way ANOVA's, were significant at baseline and weeks 1 and 2; post-hoc Tukey (p≤0.05) groupings are reported. Conclusions: Low cost carbon-based Hg sorbents can effectively mitigate Hg vapor release from dental amalgam waste. This study was supported by the Navy's Bureau of Medicine and Surgery, and the USEPA.