Mercury in the Dental Office New Regulations = New Separator Designs and Treatment

The Fallacy  It has been assumed that the dental amalgam does not leach into water.  It has also been assumed that it does not vaporize.

Reality  Based on data collected by Purves Environmental, nothing could be farther from the truth.  New instrumentation have the capability to detect lower levels of mercury in both water and air. 3  The instrument used in this study has a vapor detection limit of 1 ng/M 3.  The water detection limit is 0.08 ng/L.

Atmospheric Mercury  Measurements in the dental office have ranged from 50 to over 1000 ng/M 3.  The OSHA limit for 8 hour exposure is 1000 ng/M 3.  Measurements in the human mouth that have as little as one amalgam filling is 23 ng/M 3.  Multiple amalgam fillings as high as 900 ng/M 3.

Dental Office Atmosphere  Depending upon the dentist and the type of fillings used the office may be contaminated with mercury vapor without the knowledge of the dentist or other personnel.  The solution for atmospheric mercury is simple, Activated Carbon, preferably Iodated.  Currently there are no efficient air purification systems that use Iodated carbon.

Dissolved/Leached Mercury into Water  USEPA has proposed a new rule to require amalgam separators to be used in dental offices that discharge into a PTOW.  The rule will be in effect in September  The dentist will have up to one year to comply.  Current systems will be grandfathered in.  Dentists will be required to monitor and certify that their system is operating as established by the manufacturer.  This is where the Fun begins.

Dentists and Separators  A love/hate relationship.  Maintenance is not their strong point.  No understanding of amalgam (mercury vaporization or leaching into water)  ADA (American Dental Association)  Cost of implementation  Best Management Practice  Manufacturer’s Recommendations.  Service providers

Separator Efficiency  The separator is nothing more than a two chamber system in which the amalgam and dental waste from the operating chair is transferred by vacuum to the unit and the solids are separated from the liquid and vapor.  The separator must meet a 99% removal efficiency to be approved for use.  That leaves 1% solid to the drain. (10,000 ppm) or (10,000,000,000ng/L)

Typical Separator

Amalgam Leaching Study  Amalgam used in separator study used for leaching study. (1 gm/L) Time in hrs. Total Hg in ng/L

Leached/Dissolved Mercury from actual Separators Office Total Mercury from the Separator in ng/L Dissolved Mercury from the Separator in ng/L* 117,500,0007,500,000 27,290,0002,530, ,000452, ,000378,000 51,250,000811, ,200,0005,210, ,60036,600 Table 3 *Dissolved mercury content based upon filtration of the discharge through a 0.7 um filter.

The Data  All of the samples were taken from offices that had separators operating for at least 6 months.  Of the offices tested, only one office had a separator that had a treatment media in the separator.  That same office #3 and #7 was a “Green Dentist”. He did not use amalgam but he removed amalgams.  The media used was Sulfurized Activated Carbon.  Another study is underway with the same system in a “Non-Green” dental office.

Factors affecting Dental Office Discharges both Air and Water  Type of dentistry (Green vs Non-Green) Do they only remove amalgams or do they put amalgams in?  What type of maintenance do they perform? (internal or external)  Do they keep records?  How many chairs are in use?

Study #2 Preliminary Results  The data from study #2 using a separator with sulfurized activated carbon. Sample DescriptionDay SampledResult Back ground water sample from the discharge side of the pump. Day 1 Thursday4840 ng/L Sample from the discharge with old separator in place. Operated 5 months Day 1 Thursday87700 ng/L Sample from discharge after new separator is installed. Day 1 Thursday5050 ng/L Sample from DischargeDay 2 Friday8230 ng/L Sample from DischargeDay 3 Monday46700 ng/L Sample from DischargeDay 4 Tuesday3310 ng/L Sample from DischargeDay 5 Wednesday21300 ng/L

What Does This Mean?  Separators by themselves are not the complete answer to mercury reduction.  Treatment is necessary to control Mercury discharge from the dental office.  The majority of the discharge is dissolved mercury which is more difficult for the PTOW to remove. It is only by dilution down stream that there isn’t a greater affect.  As states move to lower the PTOWs discharge limit, mercury from dental offices will become a major issue.  Because of the Clean Water Act, the PTOWs have power to regulate dental offices.  For the dental offices, changes will have to take place.

Current Research  There are over 60,000 active dental offices in the US.  Less than 20% have separators.  The most popular unit is the least efficient.  Three companies are actively attempting to look into solutions using treatment.  One company has a treatment system but is looking for improvement.  Activated carbons are currently the only stable supply as a treatment media.

Current Plans and Challenges  To find a source that provides the best removal.  Re-design the separator to allow additional treatment or add treatment capability.  Design a system that is simple and low maintenance.  Develop a maintenance plan that improves to system operation that become a daily office routine.  Dental Office awareness. (Attempt to get the dentist and staff to understand the benefits or proper maintenance.)

What We Have Now  Manufacturers willing to get involved.  Maintenance products that improve the system efficiencies.  The European Market is ready even if the US market slow to move.  Many PTOWs are interested.

What We Need  Testing