MAXIMIZING VOLUNTARY REDUCTIONS IN DENTAL 

AMALGAM MERCURY 

Reduction in Mercury Discharges 

EPA # E0000127 

PI-98765101-0 

Brief Summary Report, November 2007 

Environmental Assistance Center 

Marie Steinwachs, Director 

200 Engineering Building North 

410 6th Street 

Columbia MO 65211 

(573) 882-5011 

moeac@missouri.edu

SUMMARY OF FINDINGS 
The use of voluntary best management practices for dental amalgam in the study area 

dental offices resulted in a measurable and significant reduction in mercury load to the 

influent wastewater of the treatment plants. 

PROJECT OVERVIEW 

The purpose of the study was to determine whether significant reductions in 

mercury discharges from dental offices could be achieved through voluntary best 

management practices (BMPs). Funding was provided by the U.S. Environmental 

Protection Agency and the American Dental Association (ADA). Springfield, 

Missouri was selected for the pilot study based on interest and commitment of 

staff resources from the Springfield Public Works Department and the Greater 

Springfield Dental Society (GSDS). The University of Missouri Extension’s 

Office of Waste Management (now Environmental Assistance Center) provided 

administration and coordination for the project. 

Influent and effluent samples were collected at Springfield’s two wastewater treatment 

plants on a bi-weekly basis for 16 months. This included four months of sampling prior to 

intervention in the form of training dental offices to implement amalgam waste best 

management practices (BMPs). Samples were collected by Springfield Sanitary Services 

chemists following EPA Method 1669 and analyzed for total mercury using EPA Method 

1631. 

Intervention 

Intervention consisted of a 1⁄2-day training course provided to area dentists on best 

management practices for dental amalgam. The eighty dentists and dental office staff that 

attended represented 54 local dental offices and 11 dental offices from other parts of 

Missouri. Participants received a DVD, wall poster with best management practices, a 

brochure of other available resources, and articles including: 

 Dental mercury hygiene recommendations 

 ADA Guidelines on Amalgam Accumulations in Dental Office Plumbing 

 Summary of Recent Study of Dental Amalgam in Wastewater 

 Missouri Dept. of Natural Resources determination of status and options for 

various types of dental waste 

 List of amalgam recyclers 

Those who completed the training course received 4 continuing education credits from 

the Greater Springfield Dental Society (GSDS), and dentists that did not attend or send 

staff to the training course received information and training materials via mail. 

Questionnaire 

A questionnaire was distributed to Springfield dentists by the GSDS and Environmental 

Assistance Center in February 2006 to collect baseline data on amalgam use and 
management practices as reported by Springfield area dentists. The questionnaire was 

adapted from a national survey of dental office practices conducted by the ADA. The 

questionnaire was sent to 123 dentists and there were 48 responses, or a 39% return rate. 

A follow up survey to dentists was distributed to 254 members of the Greater Springfield 

Dental Society (GSDS) in February 2007 to measure any changes in management 

practices after the education efforts as reported by area dentists. The response rate was 

76 dental offices or 30%. A comparison with the results of the first questionnaire 

provided insight into changes in the practices of Springfield dentists that were likely the 

result of voluntary best management practices. 

RESULTS OF WASTEWATER AND BIOSOLID ANALYSIS

Dr. Fred Eichmiller, ADAF Paffenbarger Research Center 

Biosolid 

Concentration data was collated from analysis of dried biosolid mixed from both 

treatment plants. The results showed that overall levels were very low and there was no 

statistical difference in mercury levels of treated biosolid before and after the 

intervention. 

 

Influent wastewater 

Influent water was sampled using a grab sample technique at each central plant collecting 

point and analyzed for mercury concentrations using the 1631 method. The 

concentrations were converted to mass units of mg/day by multiplying the sample 

concentration by the average daily flow rate recorded at the treatment plant on the day of 

sampling. The mass loading of wastewater influent for the NW plant with only a few 

dental offices showed a 34% reduction in mercury after the BMP training, but this 

reduction did not reach statistic significance. A similar analysis done for influent 

wastewater entering the SW treatment plant where the number of dental offices was 

approximately thirty times greater and this analysis showed a highly significant 96% 

reduction in the influent daily mass of mercury after the introduction of BMPs. 

Effluent wastewater 

Effluent water was sampled using a grab sample taken at each plant discharge point and 

analyzed for mercury concentrations. Sampling was done on the same days as the 

influent water sampling. The concentrations were again converted to mass units of 

mg/day by multiplying the sample concentration by the average daily flow rate recorded 

at the treatment plant on the day of sampling. The mean daily load of mercury in effluent 

water showed no difference between before and after the BMP training intervention for 

either treatment plant. 

Conclusions 

• The practice of BMPs in the area dental offices resulted in a measurable and 

significant reduction in mercury load to the influent wastewater of the treatment 

plants. 
• The practice of BMPs in the dental offices did not result in a measurable change 

in biosolid mercury levels. 

• The practice of BMPs in dental offices did not result in a measurable change in 

mercury load to effluent treatment water. 
RESULTS OF QUESTIONNAIRE 

Environmental Assistance Center, University of Missouri 

The comparison of responses on reported dental amalgam management practices before 

and after intervention showed indications that the BMP training and education efforts 

may have succeeded in changing some behaviors. 

Amalgam Use 

Dental amalgam use decreased 5% from the year before. 

Amalgam Capsules 

All dentists using amalgam used pre-capsulated amalgam. There was no increase after 

training in the percentage of dentists that reported using a variety of capsule sizes to 

minimize waste. A significant decrease in improper disposal of capsules in regular waste 

was observed after the training and education, while a significant increase occurred in 

dentists setting amalgam capsules aside for pickup by an amalgam recycler. 

Scrap Amalgam 

BMPs advocate the recycling of excess scrap amalgam. The collection and recycling of 

scrap increased significantly after BMP training while the improper disposal decreased. 

Medical Waste 

Medical waste incinerators are a leading source of mercury emissions. The BMPs advise 

dentists to avoid placing amalgam in containers with medical waste. There was a slight 

increase in the amount of amalgam scrap being disposed of as medical waste after the 

BMP training. This finding may indicate a need for additional education to dental office 

staff and a need for better labeling and instruction from medical waste management 

companies. 

Chair-side Traps 

The BMPs recommend capturing and recycling amalgam wastes in chair-side traps. 

There was a reported increase in the use of chair-side traps from the year before and a 

significant decrease in the practice of disposing of trap contents with regular waste 

Vacuum Pump Filters 

Most of the respondents reported using vacuum pump filters. Many dentists in the BMP 

training course were unaware that the filter and its contents could be recycled together, 

and that filters could be replaced at a cost of about $6-$7. There was an increase in pump 

filter users who reported placing filter contents in a container with medical waste, and a 

slight increase in placing filter contents in a container for pickup by an amalgam recycler. 

There was also a reported decrease in the practice of placing filter contents in with 

regular office waste

Extracted Teeth 

There was significant increase in dentists reporting that they disinfected the teeth and set 

them aside for an amalgam recycler. . 
Amalgam Recycling 

Since last year, there were an increased number of dentists who reported using an 

amalgam recycler. More dentists reported that their recycler also picks up medical waste. 

Nearly half of dentists who reported using an amalgam recycler said they pay less than 

$25 per month for the service. A smaller number of dentists who use an amalgam 

recycling service claim that the recycler picks up amalgam waste at their office, while 

more than one-third reported shipping via US mail, UPS, or other shipping service. A 

majority of dentists who recycle amalgam reported that the recycler provides packaging 

material, shipping labels and shipping manifests 

Deterrents to Amalgam Recycling 

The majority of dentists reported that they were not prevented from recycling due to the 

inability to locate a recycler in their area, locate a recycler to pick up small quantities of 

dental amalgam waste, find a method for shipping waste, or by the cost of recycling 

amalgam. 

Knowledge of BMPs 

The majority of dentists reported being familiar with the ADA’s Best Management 

Practices. In regards to staff training in BMPs, there was a large increase in dentists 

reporting that they had provided this training. There was also an overall increase in the 

understanding of best management practices after training. 

Amalgam Separators 

The majority of responding dentists did not use amalgam separators. There was a slight 

increase over the study period in the number who did report using a separator. Amalgam 

separators are not required in Missouri or in Springfield so it was assumed that very few 

would be in use. 

Bulk Mercury 

The overwhelming majority of dentists reported having no bulk mercury on the premises. 

Conclusions 

• The education and training provided to area dental offices resulted in an overall 

increase in the use and understanding of BMPs. 

• There were significant increases in the recycling of used amalgam capsules and 

scrap amalgam, and corresponding decreases in the disposal of these wastes as 

regular trash. 

• Amalgam recyclers are providing more services to area dentists, including the 

recycling of lead foil, filters, and amalgam-containing teeth. 

Acknowledgements 
The University of Missouri Environmental Assistance Center would like to acknowledge 

and thank the following people and organizations for their support and participation in 

this project: 

• Environmental Protection Agency, Region VII for funding 

• American Dental Association for funding 

• ADAF Paffenbarger Research Center, especially Dr. Fred Eichmiller, for assistance 

with all aspects of the project 

• Springfield Public Works Department for carrying out aspects of the project, 

especially Jim Burks, Karyn Highfill, Stephanie Gott, Ed Malter, Carrie Lamb, and 

Barbara Lucks 

• Greater Springfield Dental Society, especially Dr. Tom Stone, Dr. Kelly Barnett, Jean 

Harmison and the dentists of Springfield for their commitment to the environment 

• Jessica Adams-Weber, intern with the Environmental Assistance Center for assistance 

with the project.