Dental practices may be a source of a dangerous form of mercury contamination in the water supply, a small study suggests. In tests of wastewater from two dental practices, researchers at the University of Illinois found high levels of methylated mercury - a chemically altered form of the metal that is toxic to the brain and nervous system.
Mercury is part of the silver dental fillings that have long been used to treat cavities; in this form, mercury is believed to be safe.
However, when dentists use drills to remove these fillings, the tiny mercury particles that end up in dental wastewater are exposed to sulfate-reducing bacteria that convert the particles into methyl mercury. The new findings, published in the journal Environmental Science & Technology, raise the concern that dental offices may be an important source of methyl mercury in the public water supply.
"We found the highest levels of methyl mercury ever reported in any environmental water sample," researcher Dr Karl J. Rockne, of the University of Illinois at Chicago, said in a statement.
He and his colleagues estimate that up to 11 pounds of methyl mercury from dental wastewater may enter the US public water supply each year. The amount sounds small, but they note that minute amounts of this form of mercury can be toxic. The findings are, however, based on tests from only two dental practices - one "single-chair" office and one 12-chair clinic.
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