Risk communication: health risks associated with environmentally contaminated private wells versus chloroform in a public water supply.
During March 1988, 16 private residential shallow wells near a radar base in Sault Ste. Marie, Chippewa County, Michigan, were found to be contaminated with one or more environmental contaminants. The carcinogens in the groundwater were benzene, CAS 71-43-2; 1,2-dichloroethane, CAS 107-06-2; dichloromethane, CAS 75-09-2; trichloroethylene, CAS 79-01-6; and tetrachloroethylene, CAS 127-18-4. Traces of 1,1,1-trichloroethane, CAS 71-55-6, a non-carcinogen, were also detected. The source of the contamination was indeterminate at the time. In accordance with the Michigan Environmental Response Act (1), the state provided the residents, on an interim basis, with bottled water for drinking purposes.
Concurrently, the Michigan Department of Public Health (MDPH), in collaboration with the Michigan Department of Natural Resources (MDNR), began to develop a response action that would result in either site remediation or a permanent alternate source of potable water.
The public water treatment facility at Sault Ste. Marie used raw water from the St. Mary's River. The maximum concentration of chloroform, a carcinogen, in this drinking water source was 26 [[micro]grams]/L due to chlorination to meet drinking water quality standards. The system was not equipped to filter the surface water prior to treatment.
The relative health risks for the two water sources (groundwater versus public water supply) were computed. We also assisted the Division of Water Supply and the Division of Upper Peninsula (MDPH) in the communication of the relative health risks attributable to the different possible solutions to the problem. The citizens' views were fully ascertained and incorporated in the final decision for the management of the risk.
The objective of this paper is to report the relative health risks, risk communication activities, and the events that led to the final decision. An abstract of this work appeared in the Society for Risk Analysis Abstract Supplement (2).
Materials and Methods
The data on the analyses of water samples from the residential wells and the public water supply were provided by the Division of Water Supply (MDPH). The chemical analyses were conducted by the department's water laboratory.
The cancer risk assessment formulations for benzene, 1,2-dichloroethane, dichloromethane, trichloroethylene, tetrachloroethylene, and chloroform were formulated by using the United States Environmental Protection Agency (EPA) guidelines and procedures (3-7). The EPA oral slope factors (potency factors) for carcinogen contaminants were applied to compute the cancer risk assessments (8). The cancer slope factors for benzene and chloroform have since been revised (9-11). The carcinogenicity assessments for trichloroethylene and tetrachloroethylene were withdrawn by the EPA in 1992 for further review and evaluation (12-13). However, risk assessment formulations for carcinogens reported herein were made by using the scientific information available in 1988 at the time of the decision for the management of the risk (8). The standard EPA assumptions were used in formulating the risk assessments (5,7,14,15). These assumptions were: average human lifetime, 70 years; average human body weight, 70 kg; average daily water consumption, 2 L; and an acceptable risk level, 1 in [10.sup.6].
Table 1. Maximum concentration of contaminants in private wells.(*) Contaminant Maximum Comparison Concentration Value(**) ([[micro]gram]/L) ([[micro]gram]/L) Carcinogens Benzene 2 5 1,2-Dichloroethane 2 5 Dichloromethane 1 5 Trichloroethylene 8 5 Tetrachloroethylene 2 5 Non-carcinogens 1,1,1 -Trichloroethane 8 200 * The chemical analyses were provided by the Division of Water Supply, Michigan Department of Public Health, Lansing, Michigan. The chemical analyses were conducted by the department's water laboratory. ** Maximum Contaminant Level (MCL), U.S. Environmental Protection Agency (16,17).
Following the risk analysis of these data, a risk communication strategy was designed for presentation at a public meeting scheduled to discuss the environmental contamination problem. The strategy included a discussion regarding alternate solutions to the problem, relative health risks associated with each alternate solution, and how to address the public concerns.
The citizens were given the option to select one of the three possible permanent solutions for managing the public health risk from exposure to the environmental contaminants.
Results and Discussion
The maximum concentration of each chemical contaminant found in water samples taken from private wells is shown in Table 1. Except for trichloroethylene, the concentration of each contaminant was below the respective EPA Maximum Contaminant Level (MCL), which is an enforceable standard.
The risk assessment formulations and the relative health risks associated with the contaminated private wells versus chloroform in the city water supply are shown in Tables 2 and 3, respectively. The total estimated excess cancer cases attributed to the consumption of water from contaminated private wells varied from 0 to 14 per one million persons; whereas the total estimated excess cancer cases attributed to the consumption of water from the city public water supply varied from 0 to 60 per one million persons. The relative health risk posed by the consumption of the surface water from the public water supply system was approximately 4.3 times greater compared to the consumption of groundwater from the contaminated wells. Although the comparative analysis of the contaminants showed a higher numerical value (risk) for the chlorinated public water supply, one must realize that the concentrations of environmental contaminants found in private wells were very low.
At a well-attended public meeting on water contamination held on July 25, 1988 in Sault Ste. Marie, representatives of the Michigan Department of Public Health presented their findings relating to the above-mentioned risk assessment and the possible options available to manage the risk. The options available were: (a) continued consumption of bottled water; (b) connection to the existing public water supply; or (c) construction of deep private wells. The advantages and disadvantages of these available options are briefly discussed here.
It must be noted that upon discovery that private wells were contaminated, the Michigan Environmental Response Act (1) funds were used to provide bottled water to each premises. Hence, the residents could elect to continue to be provided with bottled water for drinking purposes. However, the first option was contingent on the continued availability of state funds and was considered an interim measure.
The second option recommended by the state at a cost estimated at $400,000, was to extend the city water main 5,000 feet to accommodate all of the residents. The advantages to the residents would include a relatively safe source of drinking water, which would be chlorinated and routinely monitored for coliforms, and less frequently, for metals and organic chemicals. The chlorination of water is known to be effective in reducing the risk of waterborne diseases. The disadvantages were that the water drawn from the St. Mary's River was unfiltered and influenced by a runoff in the spring when the normally low turbidity of the water is increased 10 to 20 times at snowmelt time. The raw unfiltered water would require supplementary chlorination resulting in an increase in concentration of total trihalomethanes (THMs), including chloroform. Exposure to chloroform by ingestion has resulted in the production of kidney tumors in experimental animals (11). At present, chloroform contamination ism regulated as a part of the total THMs. Four of the 10 possible THMs regulated as total THMs are trichloromethane (chloroform), tribromomethane (bromoform), bromodichloromethane and bromochloromethane. The concentrations of these four THMs are added together for expression as the total THMs for regulatory purposes (20, 21). The current maximum contaminant level (MCL) for total THMs is set at 0.1 mg/L (21, 5). The concentration of THMs in the public water supply of Sault Ste. Made has been in compliance with the MCL for THMs (20). In addition, the state law would require that all the contaminated private wells would have to be sealed or capped once city water is piped into a home to prevent use of the contaminated water for any purpose (1). Also, there would be costs associated with payment for the water and plumbing modifications.
The third option, construction of deep wells, also had its advantages and disadvantages. Discussion focused on constructing deeper wells for each of the affected residents or a single well to serve all of them. Of concern was the unknown quality of the water at a deeper aquifer level and the potential that this water may have been contaminated or could be contaminated later depending upon the existence of possible window(s) between the aquifers.
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The citizens overwhelmingly opted for the second option of connecting to the existing public water supply and, in a sense, volunteered to accept a relatively greater health risk. The residential area was connected to the existing public water supply of Sault Ste. Marie in October 1989. In accordance with the state law all the private contaminated wells were capped (1). It was a unique situation that the public values were ascertained and incorporated in the final decision for the management of the risk.
In response to the State of Michigan proposal, the City of Sault Ste. Marie later planned to further improve the drinking water quality by upgrading this public water facility by incorporation of a filtration system. This project was completed in August 1993.
In evaluating the risk communication process developed as a problem-solving approach toward risk management, several key factors emerged as essential to communicating risk. These are: clarity and accuracy of the message, important elements when developing the presentation; concern at the top of the organization to a careful and objective response; and a fair and open discussion process. These elements are critical to a successful risk communication effort. Risk communication efforts by public agencies are facilitated when the public agencies are perceived as being knowledgeable, objective, and acting in the best interest of the public.
In evaluating our risk communication effort we realized that we intuitively had included the following EPA's Seven Cardinal Rules of Risk Communication in our approach: 1. Accept and involve the public as a legitimate partner; 2. Plan carefully and evaluate efforts; 3. Listen to the public's specific concerns; 4. Be honest, frank, and open; 5. Coordinate and collaborate with other credible sources; 6. Meet the needs of the media; and 7. Speak clearly and with compassion (22). We made our best efforts to explain the pros and cons of the three options available to the citizens and put the toxicology of the environmental contaminants and chloroform in a familiar context.
Understanding the distinctions between risk and risk acceptability are critical to overcoming mistrust and communicating effectively (23). In this context, we had an extensive discussion on all aspects of the environmental problem and the possible solutions. In addition, we gave the citizens an opportunity in the decision making process to find a solution to the problem. We found that this approach enhances public trust in state and local government agencies.
In conclusion, with the incorporation of a filtration system at this public water facility in August 1993, the option voted by the citizens in 1988 may prove to be the best choice because it will reduce the concentration of chloroform in this public water system, which is already subject to the requirements of the Safe Drinking Water Act of 1986 (24).
The authors express their sincere thanks to the late Mr. Lee E. Jager for his support, cooperation, and encouragement; and to Mr. William Kelley, P.E.; James Terrian, M.D.; Mr. John Erickson, P.E.; Mr. Don Degrand, P.E.; Mr. Chuck Thomas, P.E.; and Mr. Stephen P. Gregorich, P.E., for their excellent cooperation; and to Mr. Peter Kliejunas for the review of the manuscript.
1. State of Michigan (1982), The Michigan Environmental Response Act, Public Act 307 of 1982.
2. Sidhu, K.S. and L. Chadzynski (1991), "Risk Communication: Health risks associated with private contaminated wells versus high chloroform levels in public water supply," Society for Risk Analysis, Abstract Supplement 1991 Annual Meeting, Abstr. TPM-C2. A 98-A 99.
3. U.S. Environmental Protection Agency (1986), "Guidelines for carcinogen risk assessment," Fed Regist 51 (185):33994-34003, September 24, 1986.
4. Sidhu, K.S. (1990), "State methods for regulating carcinogens, In: U.S. EPA, Risk Assessment Methodologies: Comparing EPA and State Approaches, EPA 570/09-90-012, 20, Office of Drinking Water, EPA, Washington, D.C.
5. Sidhu, K.S. (1991), Standard setting processes and regulations for environmental contaminants in drinking water: State versus federal needs and viewpoints," Regul Toxicol Pharmacol 13:293-308.
6. Sidhu, K.S. (1992), "Regulation of environmental contaminants in drinking water: State methods and problems," J Am Coll Toxicol 11:331-339.
7. Sidhu, K.S. (1992), "Current methods for assessment of exposure to environmental contaminants," Internatl J Toxicol Occup Environ Hlth 1:84-96.
8. U.S. Environmental Protection Agency (1986), Environmental Risk Assessment: Case Study (165.6), Office of Emergency and Remedial Response, Hazardous Response Support Div., Environ. Response Team, U.S. EPA, Cincinnati, OH.
9. U.S. Environmental Protection Agency (1991), Health Effects Assessment Summary Tables, OERR 9200.6-303 (91-1), Office of Research and Devel, Office of Emergency and Remedial Response, EPA, Washington, D.C.
10. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file benzene, April 14, 1993.
11. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file chloroform, April 14, 1993.
12. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file trichloroethylene, April 14, 1993.
13. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file tetrachloroethylene, April 14, 1993.
14. U.S. Environmental Protection Agency (1989), Risk Assessment Guidance for Superfund, Vol I, Human Health Manual. (Part A) Interim Final. EPA/540/1-89/002, Office of Emergency and Remedial Response, EPA, Washington, D.C.
15. U.S. Environmental Protection Agency (1989), Exposure Factors Handbook EPA/600/8-89/043, Office of Health and Environ. Assess., EPA, Washington, D.C.
16. U.S. Environmental Protection Agency (1987), 40 CFR, Parts 141 and 142. "National primary drinking water regulations: Synthetic organic chemicals; monitoring for unregulated contaminants, final rule" Fed Regist 52(130):25, 690-25,717, July 8, 1987.
17. U.S. Environmental Protection Agency (1991), 40 CFR, Parts 141, 142, and 143. "National primary drinking water regulations: Synthetic organic chemicals; monitoring for unregulated contaminants, final rule" Fed Regist 56(20):3,526-3,597, January 30, 1991.
18. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file 1,2-dichloroethane, April 14, 1993.
19. U.S. Environmental Protection Agency (1993), Integrated Risk Information System (IRIS, Online computer database), file dichloromethane, April 14, 1993.
20. U.S. Environmental Protection Agency, Region 5 (1988), "Information relating to the contamination of the 14th Street Water Supply in Sault Ste. Marie, Michigan." A letter from the EPA Regional Administrator Valdas V. Adamkus to U.S. Representative Robert W. Davis, August 22, 1988.
21. U.S. Environmental Protection Agency (1979), "National interim primary drinking water regulations; Control of trihalomethanes in drinking water; Final Rule." Fed Regist 44(231):68624-68707, November 29, 1979.
22. U.S. Environmental Protection Agency (1988), Seven Cardinal Rules of Risk Communication. OPA-87-020, EPA, Washington, D.C.
23. Covello, V.T., P.M. Sandman, and P. Slovic (1988), Risk Communication, Risk Statistics, and Risk Comparisons: A Manual for Plant Managers. Chemical Manufacturers' Assoc., Washington, D.C.
24. Safe Drinking Water Act (as amended by the Safe Drinking Water Amendments of 1986)(1986), Public Law, 99-339, June 19, 1986.
Kirpal S. Sidhu, D.V.M., Ph.D., Toxocologist, Div. of Health Risk Assessment, and Lawrence Chadzynski, R.S., MPH, Environmental Quality Specialist, Medical Waste Regulatory Program, Div. of Environmental Health, Michigan Dept. of Public Health, 3423 N. Logan St./Martin L. King Blvd., P.O. Box 30195, Lansing, MI 48909