What are radionuclides and how do they get into drinking water?
Radionuclides are naturally-occurring radioactive minerals that are occasionally present in bedrock, along with other minerals such as iron, arsenic, calcium, and silica. As ground water moves through fractures in bedrock that contains the mineral deposits, radioactive minerals can leach out into the groundwater system. Radionuclides can dissolve easily in water. The principal radionuclides that we are concerned about are radium, uranium, and radon gas. Radon gas is produced from the natural radioactive breakdown of uranium and radium.
Bedrock wells (often called artesian or drilled) may contain elevated concentrations of one or more radionuclides even if other nearby bedrock wells have low concentrations. Wells that derive water from sand and gravel deposits, also known as dug or point wells (shallow wells), generally have substantially lower concentrations or no dissolved radionuclide content.
Radionuclides exist throughout Massachusetts. In some areas the concentrations of these minerals exceed the drinking water standards for radioactivity.
How can I be exposed to radionuclides?
Uranium, radium, and radon can be taken into the body by drinking water, or breathing air. Ingestion is the most common means of getting them into the body, with the exception that radon is a gas so the primary route of exposure is via inhalation of indoor air.
How can radionuclides affect my health?
The U.S. Environmental Protection Agency (EPA) sets public drinking water standards and has determined that exposures via drinking water to certain radioactive minerals above specified levels are a health concern. Exposure to radioactivity increases the risk of developing various cancers. Other sources of radioactivity in the environment include X-rays, radiation from the sun, foods from plants that concentrate radioactivity as they grow, antique fluorescent watch dials, and many other sources.
Uranium is a health hazard only if it is taken into the body. The primary health effect from exposure to elevated levels of uranium is kidney damage. However, most of the effects seen in humans have been due to high short-term exposures, and some occupational studies have shown a reversal of kidney effects after exposure ends. Chronic exposures can also result in kidney effects. Health effects from exposure to naturally-occurring uranium in drinking water are associated with the chemical toxicity of uranium. EPA set its drinking water standard for uranium primarily on its chemical toxicity, but as a precaution also considered the potential for uranium to cause cancer after a lifetime of drinking water exposure, under the assumption that any constituent that has radioactive properties could cause cancer. Skin exposure is generally not a major concern.
Radium is a health hazard when it is ingested. Some of it is excreted from the body with waste but a portion of it may accumulate in bone. This accumulation may, over time, result in an increased risk of bone cancer, leukemia, and lymphoma. A significant concern regarding the presence of radium is radon, which is produced from the radioactive decay of radium.
In addition to cancer risks from ingestion of radon dissolved in water, the greater risks from radon exposures are associated with inhalation of the gas, which may increase the risk of lung cancer.
What are the health standards for radionuclides in drinking water?
The federal standards set to protect public health for radioactivity in public drinking water supplies are called Maximum Contaminant Levels (MCLs). MCLs are based on an individual consuming 2 liters of water a day for a lifetime. The EPA finalized new MCLs for radionuclides in drinking water for public water systems in 2000. However, these standards only legally apply to community public water systems and may serve as guidelines for all other drinking water supplies. There are currently no federal or state standards established for private wells (a well that serves less than 25 people) or other non-community public water systems (wells supplying schools, factories, shopping centers, etc.). Private-well standards may be set by the local board of health (BOH) and are typically the same as the state and federal Public Water Supply (PWS) standards. While EPA does not have a standard for radon in drinking water, Massachusetts has established a radon guideline, included in the table below.
|Compliance Gross Alpha
|Radium 226 + Radium 228
1 Current Massachusetts Regulatory Limit: MassDEP Office of Research and Standards Guideline (ORSG) triggering indoor air testing
Do I have radionuclides in my water?
If you are served by a community public water system, you can contact the utility for specific information on radionuclides in your water. Consumer Confidence Reports (annual water quality reports) issued by the utility in early summer will also contain this information. If a standard is exceeded, the utility must notify customers.
If you have a private well constructed in bedrock, you should have the water tested to determine if radionuclides are present. For a searchable listing of MassDEP Certified Laboratories, see MassDEP's Certified Laboratories.
The concentration of radioactive minerals in well water can vary substantially based on rainfall and other factors. Thus, at least two samples (taken a month or two apart, if possible) should be taken before conclusions are reached regarding the average concentration of any radionuclide. The recommended approach is to request that the laboratory first test for gross alpha. If the is gross alpha result is less than 5 picocuries per liter (pCi/L) then no testing for radium 226, radium 228, or uranium is needed, because the results will be below the public drinking water standards. If the gross alpha result is equal to or greater than 5 pCi/L, then testing for radium 226 and radium 228 should be requested. If the gross alpha result is equal to or greater than 15 pCi/L, then testing for uranium should also be requested. Typical laboratory analytical costs for drinking water samples are:
|Approximate Cost per Sample
|$20 to $45
|Gross alpha radiation
|$60 to $150
|Radium-226 and Radium-228
|$60 to $100
Can radionuclides in drinking water be treated?
Yes. All naturally occurring radioactivity can be treated. However, different radionuclides require different types of treatment. In general, uranium and radium only need to be removed from water that will be consumed or used in food. The primary health risks associated with radon gas are from inhalation. Radon, if present in drinking water, enters the air in the home as it off-gasses from water that pours from faucets and shower heads and that is used in dishwashers and clothes washers. Therefore, radon removal requires treating all of the water that enters the home. In addition, the homeowner should be aware that radon gas can infiltrate the house from the underlying soils through cracks, holes and openings in foundations, and this potential source of radon to indoor air should be considered in evaluating indoor air radon exposures and may require a different treatment system than that which would be used for water as a sole source of radon. See EPA's A Citizen's Guide to Radon for more information regarding radon gas in the home.
The implications to the private well owner are that point-of-use systems (i.e., treatment systems that only treat the kitchen tap water) may be all that is required for uranium or radium removal. However, point-of-entry systems (i.e., treatment systems that treat all of the water that enters the home) would be required for radon gas removal from water. The presence of other naturally occurring minerals in the water may increase treatment costs.
|Radium 226, Radium 228
|Cation exchange, manganese greensand filters, or reverse osmosis
|Anion exchange or reverse osmosis
Reverse osmosis (RO) is most commonly used for point-of-use systems for removal of uranium in private wells. A recent cost survey conducted by the New Hampshire Department of Environmental Services (NHDES) indicated that the median cost to install a point-of-use treatment system for uranium removal was $1,595, with median annual maintenance costs of $185. Anion exchange is most commonly used for whole-house treatment systems for removal of uranium. The same NHDES survey indicated a median cost of $2,450 to install a whole house treatment system for uranium removal, with median annual maintenance costs of $120.
Aeration systems are the preferred method for radon removal. The NHDES survey indicated a median cost of $4,000 to install a whole house treatment system for radon removal, with median annual maintenance costs of $200. This cost is only for the treatment of radon in water and does not include the cost to install a separate sub-foundation ventilation system for removing radon gas from beneath the house before it can seep into the home.
The NHDES survey did not specifically address cost estimates for the installation of radium removal systems.