ELKHART — Indiana environmental officials report higher-than-allowed levels of mercury in the discharge from Elkhart's wastewater treatment plan and it's prompted calls for a remediation program involving dentists' offices, the suspected source of the metal.
According to a Dec. 31 violation letter from the Indiana Department of Environmental Management, or IDEM, to the city of Elkhart, routine city testing indicates that the average mercury levels for June, August and October of last year exceeded the allowable limit, 1.6 nanograms per liter of water.
The 1.6-nanogram limit, which went into effect last June, represents a sharp reduction in the previous maximum-allowable limit, 120 nanograms per liter, said Laura Kolo, utility services manager for the Elkhart Public Works and Utilities Department. Whatever the case, the city still must act on the violation of the newer, more stringent limit, and Kolo said Tuesday, Feb. 4, that the effort here will focus on dentists' office.
A nanogram is one billionth of a gram.
Elkhart has no known industrial operation that would be behind the mercury, Kolo wrote in a written response to IDEM on Jan. 17. Thus, "we have concluded that further action needs to be focused on dental offices," she wrote, citing a 2002 report that found that dental clinics are the primary source of mercury emissions at public wastewater treatment plants.
She told members of the Elkhart Board of Public Works Tuesday that the plan here will call on dentists' offices to voluntarily start using amalgam separators to help capture mercury, used in some fillings and discharged into the wastewater system, potentially, when such fillings are drilled out of patients and removed. That'd be cheaper and more effective than implementing some sort of mercury treatment operation at the wastewater plant.
If the voluntary program yields no cooperation, the city could move to a mandatory program, Kolo said. She said she hopes to have the outline of a formal treatment program ready for consideration by city officials by late June.
Notwithstanding the discharges in question into the St. Joseph River, Kolo didn't indicate that the public should be alarmed, noting the much more stringent limit, 1.6 nanograms versus 120 nanograms per liter of water, based on average readings over extended periods. The highest individual reading here was 4.4 nanograms in a June 2013 measurement.
Dentists should use amalgam separators, "to catch and hold the excess amalgam waste coming from office spittoons," the U.S. Environmental Protection Agency advises. "Without dental amalgam separators, the excess amalgam waste will be released to the sewers via drains in the dental offices."
Mercury, according to the federal agency, can impair neurological development in infants and children.