MERC Vermont | Advisory Committee on Mercury Pollution Meeting Minutes

Meeting #39: Thursday, September 5, 2002
Time: 9:00 a.m. to 12:00 p.m.
Location: Skylight Conference Room, Department of Environmental Conservation
Waterbury State Complex, Waterbury, Vermont

Members Present:
Michael Bender, Abenaki Self-Help Association, Inc.
Mary Canales, School of Nursing, University of Vermont
Neil Kamman, Agency of Natural Resources, Water Quality Division
Rich Philips, Vermont Agency of Natural Resources, Environmental Assistance

Guests Present:
Peter Berglund, P.E., Metropolitan Council Environmental Services, Minnesota (Phone)
Owen Boyd, SolmeteX™, Northborough, Massachusetts
Dr. Daniel Ferraris, DMD, South Burlington
Tony French, Consultant
Sarah O'Brien, National Wildlife Federation
Mark Stone, MS, DDS, Mercury Mgt. Program, Naval Dental Research Institute
Peter Taylor, Vermont State Dental Society (VSDS)
Greg Lutchko, Vermont Agency of Natural Resources, Environmental Assistance
Gary Gulka, Vermont Agency of Natural Resources, Environmental Assistance
Karen Knaebel, Vermont Agency of Natural Resources, Environmental Assistance

The meeting location was moved and the Committee members and interested parties gathered in the Skylight Conference Room of the Waterbury State Complex. Rich Phillips called the meeting to order.

Because of limited time, the Committee decided to move review of the work plan to the October meeting.

Agenda Item 2-
Update on amalgam separator and clinic loading study Peter Berglund, P.E., Metropolitan
Council Environmental Services, Industrial Waste & Pollution Prevention Section.

Peter Berglund attended the meeting via telephone. Mr. Berglund advised the Committee that his Agency had two main studies: evaluation of amalgam separators and loadings from dental clinics measured at vacuum systems.

conducted because of % of contribution detected in first study
idea was to install equipment, treat wastewater and then look at sludge generated at plant
focused analytical work on sludge measurements
established baseline and during time equipment was installed
two separate sewage treatment locations
about 13 dentists in both locations
average reduction of 29% at one treatment plant and 44% at the other
29% reduction was because that treatment plant had a more aggressive grit chamber
another part of study was to back calculate what the expected loading would be 120- 234 mg (range) per dentist per day
used mostly settling type of amalgam collector - sold out of Seattle - settles over night - collects in container

Question as to mercury mass loading - fairly typical number or somewhat unique?
- 8 plants - in general mercury was uniform in all plants - two cities had a small amount of industrial contribution
- worked on one case study for the area -compared mercury from dental clinics and residential sources - measurements fairly uniform
- residential and commercial flow everywhere around the country all showing small (5-10%) industrial contribution and significant dental and significant residential contributions.
Question if the mercury measured in sludge is broken down and amalgam measured independently?
- The sludge is incinerated and comes back to the treatment plant via used scrubber water.
- No separate quantification of amalgam- amalgam incinerated and it is all measured as total mercury.
Question as to whether the practice patterns of dentists were evaluated?
- Installed in general practice clinics - some were using amalgam, some dentists didn't place amalgam but removed it.
- Clinics all logged placements and removals.
Question if in the test of sludges was the test done to determine the total mercury in solids?
- Yes, to keep the study manageable they did not analyze the effluent.
Question if this study only included dentists on municipal waste water systems?
- In Minnesota, commercial cannot be on septic tanks.
Question as to whether the installation of separators will be a voluntary approach?
- Nothing finalized - might be voluntary - if clinics do not eventually install, it will be mandated.
Question if Minnesota is thinking toward establishing a treatment standard?
- Still part of negotiation with Dental Association
- ISO standard of 95% is not adequate
- ADA ran a test and set a benchmark - everyone is using ISO except Toronto.
- ISO uses amalgam particle size over 3mm
- 60% are over 500 microns
- trap pulls out materials over 700 microns
Question as to how Minnesota deals with mercury in the pipes?
- Some dentists use nitric acid to clean X-ray equipment - as a part of BMP they push clinics to control Ph of wastewater. For residual mercury in pipes it is an onerous task to clean out pipes.
- First recommendation is to install separators, as time goes by, look at pipes if cleanup is warranted.

Agenda Item 3-
Discussion of research findings: "Determination of Biologically Available Forms of Mercury in Dental-Unit Wastewater" and "Residual mercury content and leaching of mercury and silver from used amalgam capsules" Mark Stone, MS, DDS, Project Manager Mercury Management Program, Naval Dental Research Institute.

Monomethyl mercury (MMHg) was found to be present, in important concentrations, in dental wastewater from three locations in two different treatment facilities from sampling over the 18-month study period. The highest concentrations of MMHg were found to be present in the holding tanks of the 107 and 30-chair clinics. Lower, but still environmentally significant concentrations of MMHg were measured at the dental chair. The amount of MMHg is low in comparison to total Hg yet noteworthy when the toxicity of MMHg is considered. The concentration of MMHg in dental wastewater samples is orders of magnitude greater than in environmental samples.

Within a series of samples collected over several days, MMHg concentrations are relatively consistent; but large differences between values from samples taken several months apart are sometimes recorded. Conversely, MMHg values from chair side samples were much more consistent throughout the study. Variability seen in holding tank samples may be associated with the residence time of wastewater in the tanks, the amount of rinse water used in the clinics as well as wash down cycles used in some dental vacuum systems.

The higher concentration of MMHg in samples from holding tanks compared to chair side samples is likely the result of methylation of inorganic Hg by bacteria and fungi. The biochemical mechanism of methylation is only superficially understood, but both biotic and abiotic mechanisms are known to occur. Methylation of inorganic Hg has been shown in sediments and found to be the result of sulfate reducing bacteria. The higher concentrations of MMHg seen in holding tanks where bacteria grow and prosper strongly suggest bacteria to be the source of the MMHg (although abiotic methylation via the coenzyme methylcobalamine, a Vitamin B-12 analog, cannot be ruled out). The source of MMHg formation in the dental-unit wastewater stream is an area of ongoing research.

Sulfate Reducing Bacteria (SRB) are known to populate the oral cavity of healthy patients as well as patients with periodontal disease. A recently published report correlates MMHg levels in human mouths to the number of Hg containing restorations present, suggesting methylation may occur in the oral cavity. An earlier paper demonstrated the methylation of inorganic Hg by oral streptococci in vitro. SRB in the oral cavity may provide a mechanism by which dental waste water is "seeded" with these bacteria.

The presence of Hg in dental wastewater is an obvious concern for dental clinics, but also an important issue for municipally owned wastewater treatment plants. These facilities use bacteria in the treatment process and Hg provides a substrate for microbial mediated methylation. Significant concentrations of Hg have been measured in the influent of wastewater treatment facilities. A nine-week study tracking Hg pathways at a large Midwestern plant revealed an average daily Hg loading of 248 grams. The Hg removal efficiency was determined to be 96%; resulting in the release of 4% of the Hg (approximately 10 grams per day) into the Mississippi River.

Question if all the methylated mercury in study came from holding tanks
- Collected wastewater pretreatment in batches
- Tried to identify bacterial-fungi or other organisms
- Belief that additional methylation occurred in holding tanks
Comment that Navy clinics are huge and have identifiable special circumstances
- Treat large amounts of people
- Use amalgam - no other material that can replace it in all parts of the mouth
- No time and no access to use other types of materials - there is potentially only one day allocated for dental
Question as to whether it is a concern for the total amount of mercury going out - is it a flaw of the ISO method?
- In vitro type of sample
- Install in clinic and see what real numbers are
- Average values - 9 out of 12 remove over 99%
Question of the types of amalgam separators, which were evaluated by the Navy as to whether all units addressed dissolved mercury and if this, was the most aggressive type of removal.
- Response was that only two systems removed dissolved mercury
- Mr. Stone felt this was the most effective type of unit
- Suggestion that the Committee evaluate those units that remove the dissolved mercury as well as particulates
- Vermont State Dental Society felt uncomfortable in only evaluating two systems without more information about other types of units.

Study solid waste issues
As many as 11,000 -12,000 capsules per month are used in one Navy dental clinic
Originally reusable capsules were used
Visually inspect capsules to see mercury
Mixers were contaminated
Encourage manufacturers to recapsule
Some amalgamators (mixing machines) were disposed of
10 brands of capsules studied
capsules were segregated into three groups according to the function of the capsule design- more complicated capsule designs may tent to retain more amalgam and therefore more mercury
- the highest levels of retention in this study were in the case of "Disprsalloy" because the pestle added increased surface area where the amalgam and mercury could adhere. Pestal containing capsule - 0.59 to 1.5 mg with new design
- ultrasonically fused capsules retained the next highest amount of mercury because of a groove that tends to retain amalgam
- third group is the simplest capsule design
Leaching test with capsules - over RCRA level
Retorting facility - $1200 for 55 gallon drum

Agenda Item 4-
Discussion of how amalgam separators work - Owen Boyd, Solmetex.

Amalgam separators are nothing more than filters placed in dental settings. Centrifuge separators created smaller particles from larger ones. Standard filtration or mechanical filters are designed to work on settlement of particles with a 90-95% reduction. Settlement filters are inexpensive but there is a problem in dental settings due to negative pressure created in the vacuum system. It is a waste of time to deal with a 5 micron filter (particle size distribution in ISO standard) inside a vacuum line.

In the Solmetex system, they slowed down the flow in an air expansion unit to drop the particles into a lower chamber to get rid of the smaller particles. Along with the mechanical filter there is another chelex filter, which is an absorbent for dissolved mercury. It doesn't take a lot of contact time to absorb mercury. About one liter of fluid per day passes through the system.

Inexpensive but was adequate to do the job
Below a ppb - more expensive filter
Change by law - 10 ppb at sewer connection no matter what filtration system
In place and maintained they will hold to limit
Have sanitant into stream from resin that disinfects 24 hours a day- keeps resin from fouling and lasts one year.
Maintenance every 6 months
Permission from 49 states which will allow Federal Express to come in and pick up cartridge - reverse label to Wisconsin for retort - recovered for reuse
Program is in place - agreements with dental societies in US - $48. per month per practice
Has fill line on system allows dentist to monitor system
Installed by plumber - typical installation by flex tubing - never had to alter a room for space - designed to be flexible - left/right/anywhere
They send a card to dentist - time to pick up filter - invokes a phone call - keep track and make certain maintenance is done

Samples do not work on a vacuum system - methylation in system
Nicholas Blum took spike sample sand sent them out to every single state - variance of results
ADA study
- Needs to be an organization where dental offices can feel secure
- ISO standard does not include mercury
- All venders to include how much water
- Most systems 750 ml per minute after vacuum pump - in front of vacuum line, lesser flow rate
- ISO by independent testing lab - numbers are good
- Effluent levels - certain systems have different levels - weak at best
- ADA filtered - added mercury back in
- Dentists vary from one practice to the next
- Technology not tested insitu - done in lab testings
- Important to know flow rate unit is tested under - many work only for small flow rate - one of the systems uses lots of volume to flush (Peter Berglund)

Agenda Item 5-
Update on STEP project findings (Massachusetts Dental Amalgam Separator Project)- Michael
Bender, member of Technical Workgroup and Greg Lutchko, EAD.

Mr. Lutchko suggested that perhaps since Mr. Bender was on the technical workgroup that he
would have more insight into the project. The group believed that there was struggle with
coordination between data in the lab and what is occurring in the field. There was concern that
the project included rinsing of the lines in the dental office by taking a garden hose and running
water through the system. At 5 gallon per minute, this would ruin the integrity of the system.
Perhaps the best method would be to start over and allow the manufacturer to bring in new
units. The purpose of this project was to develop a protocol with a quick test of equipment.
The group felt there were too many variations in the testing that was unaccounted for in the
data. Mr. Berglund suggested that the goal is to come up with a good yardstick. ISO uses
large particles and doesn't address dissolved particles. STEP is trying to come up with
improved bench-top method but the project is not complete. There was a suggestion from
other information provided by the STEP project that the maintenance was crucial to the success
of any unit and that in some cases the maintenance was the draw back to some systems that
might have shown more success.

Agenda Item 6-
Status of DEC/EAD evaluation of dental amalgam separators. Greg Lutchko, EAD.

The Department is anxious to move forward on the amalgam separator issue. There is
information out there on available units that meet all expectations such as ease of maintenance
and performance issues. However, what we are lacking are units in Vermont.

EAD suggested that they were not able to endorse a specific product or vendor but could only
establish standards to guide dental offices in their selection of products. What these standards
would be was uncertain; whether to set performance standards for percentage removal limits
or to set an effluent concentration based limit. EAD's evaluation of the science believes that
Vermont can do better than the ISO standard in addressing dissolved mercury in order to
realistically deal with the effluent limit.

EAD suggested that the dental society consider evaluating the efforts of other state dental
associations. EAD also suggests coordination with the dental society to continue voluntary
efforts to address the mercury amalgam issues. EAD suggests a pilot project for a couple of
units in Vermont to determine cost, ease of use, performance, maintenance, and reliability.

Peter Taylor told the Committee that the Agency was scheduled to speak at the Vermont State
Dental Society's annual meeting for about a half hour and set up a booth at the exhibit hall. He
anticipates attendance of around 500 dentists and staff.

Regarding the issues surrounding amalgam separators, Mr. Taylor advised the Committee that
he had hoped to obtain a sense of direction and how to approach the issues. He told the
Committee that he believed dentists were willing to cooperate and that addressing this matter
could be relatively painless but it was important to look at all separators and make a
determination as to which were best.

Mr. Taylor believes the following are items that should be considered to assist dental offices:

Testing of the product and the ease of maintenance of all separators.
Exploring the newly discovered issue regarding amalgam capsules and their disposal
Obtaining a list of manufacturers of separators.
Creating a list of recycling companies for recycling of all products including contact and non contact amalgam (Provide this information to dental offices)
Determining non governmental organizations that could assist
Creating a feedback form on the Dental Society's web site

Suggestion to conduct a pilot project with Vermont Dentists
- Concern that a pilot project would be huge endeavor and tests already being conducted elsewhere
- Pilot project would be to evaluate products rather than to test waste water discharge
- Suggestion that amalgam separator manufacturers may potentially be willing to allow their products to be tested by dentists to evaluate effectiveness, cost, and ease of use regarding maintenance.
- Suggestion that the amalgam separator manufacturers chosen for the pilot have some sort of provision (which is provided for in the maintenance program of their product) that provides for the disposal of the captured amalgam particles.
- Suggestion that the Department be involved with the pilot and agree what is included.
- Suggestion that units should also deal with soluble discharge as well as particulates.
Suggestion to develop a Memorandum of Understanding between the dental society and the Department as did Massachusetts and Rhode Island.
Suggestion to fall back on the data of the ADA and ISO.
Suggestion to establish small sub committee, involving technical experts, to sift through the information on amalgam separators and report back to the Advisory Committee.
- Best Management Practices has a placeholder for separators, a committee could produce something that is workable to include in the BMPs.
- Suggestion that a sub committee could evaluate a process for approving units by either using the current protocol or bring the limits up to a 98-99% recovery rate.

The next meeting was set for October 10, 2002 from 9:00 a.m. to 12:00 p.m. in the conference room at the Environmental Assistance Division, Waterbury state complex, Waterbury, Vermont.

Agenda items include update on all work plan items, update on sensitive populations sub-committee. In addition, the Committee considered a possible conference call with experts on the dental amalgam separator issue.

Meeting date was changed from October 10th to October 29, 2002 from 9:00 a.m. to 12:00 p.m.

Copies of studies referenced in this document can be obtained by contacting Karen Knaebel at (802) 241-3455.


		Vermont Agency of Natural Resources Advisory Committee on Mercury Pollution