Managing Mercury in Dental Offices Greg Newman Division of Pollution Prevention and Environmental Assistance

OUTLINE n Background n Mercury in North Carolina n Mercury in Wastewater n Sources of Dental Mercury Discharges n Preventing Mercury Releases n Treatment

Mercury: Background

Products / Chemicals Containing Mercury n Thermometers n Manometer (pressure gauges) n Tilt switches n Thermostats n Fluorescent Lights n Sulfuric Acid (lead smelting) n Caustic Soda (chloro-alkali) n Chlorine Bleach (chloro-alkali) n Chlorine Gas (chloro-alkali) n Textile fabric (biocides) n Overall Use of Mercury Down 97% ( )

Environmental Effects of Mercury n Once in water bacteria convert Hg to Methyl Mercury - Neurotoxin n Methyl Mercury Biomagnifies –Binds to Proteins of Fish »Bass & Bowfin Most Affected

Mercury Emissions to the Environment n Total of 3300 tons annually n Natural Sources –Oceans, Rocks, Volcanoes, Plants

US Manmade Mercury Sources n Combustion Contributes 83% of U.S. Hg Emissions (285 tons ) n Mercury from Combustion Falls Back to Ground with Rain –Washes into Rivers and Lakes

Mercury in Wastewater n POTWs Usually think in ppm or ppb n Need to Think in Sub-ppb (parts per trillion) n 1 fever thermometer (0.5 grams) contaminates 11 million gallons of water

Mercury in North Carolina

Fish Advisories in North Carolina

Update on Mercury Situation in NC n Fish Consumption Advisories for Lumber River Basin, Baytree Lake, & added Phelps Lake in ‘96 –Total More than 10% of States Land Area n NC Advisories from Atmospheric Deposition –Phelps Lake is Land Locked (No major influent, surrounded by State Park)

Dental Mercury Contributions

n Estimates on POTW Mercury Loading from Dentists Range from Negligible to Nearly 60% of Total n Many POTWs Believe Dentists are one of the Last Direct Dischargers or Mercury Mercury from Dental Discharges Duluth, Minnesota 4

n Amalgam 1:1 mix of Mercury & Alloy Powder n Only About 45% Ends Up in Tooth Filling (Rest down the drain through traps and vacuum system) n Major Amalgam Particles Caught in Screens, some smaller particles caught in traps n Significant Pass-thru of Minor Particles –Increased surface area of small particles increases mercury solubility Mercury from Dental Discharges

Dental Waste Continued... n Low Flows (< 1 Gallon per patient) n High Concentration (1-15 ppm Hg) n Theoretically, 1 gallon Dental Wastewater at (3 ppm) puts 1 MGD over WQ Standard

Preventing Mercury Releases

Amalgam Management n Goal: Prevention of amalgam releases to the environment n Methods include: - product substitution - improved housekeeping - separation - recycling

Amalgam Management – Priorities n Prevent introduction to City sewer n Prevent incineration (red bag waste) n Recycle or manage as hazardous waste n Keep mercury spill kit on site

Dental Office Waste Management

Amalgam Management MANAGEMENT STRATEGIES n Use precapsulated amalgam. n Establish contract with recycler - Recycle all contact and non contact mercury (list) n Amalgam traps and filters should be shipped to a recycler or collected by a hazardous waste hauler. Separate contact from non-contact amalgam n Change chair side traps once per week. Flush lines at end of the day and change traps in morning. n Use disposable traps as it is difficult to remove amalgam from reusable traps and the material is often washed to sewer

Amalgam Management MANAGEMENT STRATEGIES n Don’t rinse traps or filters over drains - Retrieve excess amalgam with gauze and recycle. n Remove amalgam from instruments with gauze prior to washing and recycle. n Secondary filters in vacuum systems should be changed once per month or according to manufacturers specifications n Store any waste amalgam in designated airtight container. TRAINING n Train all employees n Maintain a log RESULTS n 75% removal of amalgam

Mercury Treatment Equipment

Dental Amalgam Wastewater Technologies n Screening Filters –Simple Wire Screens Protecting Vacuum Pumps –Change to finer mesh (20 for 100) close to 90% Removal n Sedimentation –Vary from simple inexpensive traps to large Multi- phase Units $200 - $1,000, claim 95% removal n Ion Exchange –Cationic & Anionic polymers capture small particles of Hg usually after sedimentation –$1,500 and up, claim 95% removal n Centrifuge –Spin larger particles out to the sides of the vacuum pump for collection –$2,500 and up, claim 95% removal n Cross flow microfiltration with precipitation n Traditional Metal Scavenging Polymers

NC Efforts to Reduce Wastewater Dental Mercury n Tryon exploring permits n Whiteville and Fuquay-Varina strongly encourage / require installation of treatment equipment n Whiteville received grant to conduct evaluation of removal equipment

Questions / Comments n Greg Newman (919) Web: www/p2pays/org (919) Web: www/p2pays/org