Why was testing of private wells conducted and who conducted this study?
Due to an improved understanding of the impacts of arsenic and uranium on human health, the U.S. Environmental Protection Agency (EPA) established drinking water standards for arsenic and uranium. However, without testing, it can be difficult to determine which private wells may have arsenic or uranium present in levels that exceed the standards. The U.S Geological Survey (USGS) study was conducted to identify geologic characteristics that may help identify areas with higher probability of contamination from arsenic or uranium. Note that the study examined only naturally occurring arsenic and uranium levels, not arsenic and uranium levels due to releases of these chemicals from industrial or other man-made processes.
In 2003, the U.S. EPA established the drinking water standard of 30 parts per billion (ppb) for uranium in public drinking water supplies. In 2001, the EPA changed the public drinking water standard for arsenic from 50 ppb to 10 ppb; this standard became effective in 2006.
The purpose of the USGS study, which began in 2008, was to determine whether there was a correlation between the presence of arsenic and uranium in wells completed in bedrock and the type of bedrock. This information would be used to guide future public water supply exploration activities. An additional benefit of the study is that the information can be used to determine whether or not a private bedrock water supply well is in an area with a higher or lower probability of exceeding either of these standards.
The study involved laboratory analyses of private bedrock well samples collected by 478 private well owners located in 116 communities in central and northeastern Massachusetts. The study area was selected based upon a review of existing public bedrock well records, which indicate that higher arsenic concentrations occur in this area. Less is known about the distribution of uranium in bedrock well water. The study included uranium analysis in order to obtain a better understanding of its possible correlation with types of bedrock in Massachusetts. The USGS and the Massachusetts Department of Environmental Protection (MassDEP) jointly funded the private well study.
To address any potential concerns about individual health impacts associated with arsenic and/or uranium detected in private well water samples taken during this project, the Massachusetts Department of Public Health (MDPH) offered urine testing as a public service to a subset of participants of the USGS study. Contact MDPH for more information at 617-624-5757 or 800-240-4266.
Should I be concerned about arsenic and uranium in my private drinking-water well?
In order to determine whether or not you should be concerned about arsenic and uranium in your private well water, you would first need to know what levels are present in your well water. MassDEP and MDPH recommend that all homeowners test their wells for arsenic and radionuclides such as uranium. If the results of initial and follow-up testing exceed the public drinking water standards, then you should consider installing a water treatment system to achieve these standards.
While I am waiting for the test results, is it safe to drink my water? Or to bathe in it?
Yes. Based on information available on water testing results and the MDPH companion effort testing for arsenic and uranium in urine, the probability that anyone's well poses a health concern is very low. However, we recommend you get your water tested. Living in an area where the USGS testing indicates groundwater has a greater chance of exceeding the arsenic and uranium drinking water standards does not necessarily mean that your well will have a problem. In fact, we expect that the majority of private wells in these areas will not exceed the standards. So, it is likely, but not certain, that your water will be below the standards. The only way to know for sure is to have your well tested. In the meantime, if you are concerned, you may consider using bottled water until you get your test results.
The public drinking water standards for arsenic and uranium are 10 micrograms and 30 micrograms per liter of water, respectively (or 10 ppb and 30 ppb, respectively). Drinking water standards are set by the US Environmental Protection Agency to protect public health. They are based on an individual consuming 2 liters (approximately 2 quarts or 8 cups of water a day) of water every day for a lifetime. Actual health risks depend on the three key factors: the level of arsenic and uranium in the drinking water; the amount of water actually consumed from your private well; and how many years the water is consumed. Risks are reduced if you ingest less than 2 liters a day or consume the water for less than a lifetime.
Why might arsenic and uranium be present in bedrock well water?
Some areas of New England may contain naturally higher levels of arsenic and uranium in bedrock than other areas of the region. Arsenic can be found in two different forms: organic arsenic and inorganic arsenic. The inorganic forms of arsenic are generally found in groundwater and pose a greater health concern than the organic forms of arsenic (which are present in some foods, e.g., fish) that are considered less toxic. Through natural processes, arsenic and uranium can leave the rock and enter the groundwater in the bedrock. If a bedrock well is installed at a location that intercepts groundwater containing relatively high concentrations of arsenic and/or uranium, then arsenic and/or uranium withdrawn from the well may exceed the public drinking water standards.
What are the drinking water standards for arsenic and uranium?
The state and federal public drinking water (PWS) standard for arsenic is 0.010 milligrams per liter (mg/L) (or 10 parts per billion ppb). The drinking water standard for uranium is 0.030 mg/L (or 30 ppb). Private well standards are determined by the local board of health (BOH) and are typically the same as the state and federal PWS standards.
Did the study show a correlation between geology and arsenic concentrations in bedrock wells?
Yes. The 478 bedrock well water samples collected for the study were distributed amongst the many different types of bedrock geologic units that are mapped in the study area. The results indicated a correlation between the probability of exceeding the public drinking water standard for arsenic and the type of bedrock. The study also indicated a strong correlation between arsenic concentrations and the well's proximity to the Clinton-Newbury fault zone. The Clinton-Newbury fault zone extends from near the eastern end of the Massachusetts and Connecticut border in the south to the Merrimack River Valley in the northeast.
The USGS predicted the estimated number of wells within the study area expected to exceed the arsenic standard by multiplying the probabilities obtained from the sample results by the estimated number of wells in the area.
This method resulted in a prediction that approximately 5,700 residential bedrock wells out of 90,000 in the study area may have arsenic concentrations that exceed the public drinking water standard. The USGS estimated that approximately 3,800 of these 5,700 wells are not being treated for arsenic.
Did the study show a correlation between geology and uranium concentrations in bedrock wells?
Yes. The results of the 478 samples collected for the study indicated a correlation between the probability of exceeding the public drinking water standard for uranium and the type of bedrock. In general, wells completed in granitic (granite type) bedrock units had the greatest probability for exceeding the standard.
The USGS predicted the estimated number of wells within the study area expected to exceed the uranium standard by multiplying the probabilities obtained from the sample results for each individual bedrock unit by the estimated number of wells in each unit. This method resulted in a prediction that approximately 3,300 residential bedrock wells out of 90,000 in the study area have uranium concentrations that exceed the public drinking water standard. The USGS estimated that approximately 3,000 of these 3,300 wells are not being treated for uranium.
What percentage of samples exceeded the public drinking water standards for arsenic and uranium?
The results of 478 private well samples from 116 towns that were collected and analyzed for the USGS study are as follows:
- approximately 13% of the samples collected from randomly selected well locations exceeded the 10 ppb public drinking water standard for arsenic
- less than 3% of all samples collected exceeded the 30 ppb public drinking water standard for uranium.
What are the potential health effects associated with high levels of arsenic in drinking water?
Short-term exposure to drinking water with higher levels of inorganic arsenic may lead to nausea, vomiting, diarrhea, cardiovascular effects, and brain effects (i.e. encephalopathy), as well as decreased production of red and white blood cells and impaired nerve function. Long-term ingestion of drinking water with inorganic arsenic may lead to a pattern of skin changes (e.g. patches of darkened skin, small "corns" or "warts" on the palms, foot soles, and torso) and damage to the nervous system (i.e., peripheral neuropathy). Several studies have also shown that long-term exposure to inorganic arsenic can increase the risk of certain cancers, including lung, skin, bladder, liver, kidney, and prostate.
What are the potential health effects associated with high levels of uranium in drinking water?
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. US 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.
Are there radionuclides other than uranium that I should be concerned about?
The USGS study only investigated the occurrence of arsenic and uranium in bedrock well water. Other naturally occurring radionuclides, such as radon gas and radium, are commonly found in the same types of bedrock as uranium. Therefore, although no probability data exists for radon gas and radium, areas with increased probability for increased uranium concentrations generally would have an increased probability for elevated radon and radium concentrations. See the Radionuclide Q&A for additional information regarding radon and radium public drinking water standards, health effects, and treatment options.
Are public water supplies at risk for arsenic or uranium in their water?
No. Public water supply wells that serve residences are tested for arsenic and uranium. Any public water system that can not routinely meet the public drinking water standards is required to provide treatment. They are also required to report any water quality results that exceed the public drinking water standards in their annual Consumer Confidence Report that is made available to their customers.
Where can I have my well water tested for arsenic, uranium and other radionuclides?
For a searchable listing of MassDEP Certified Laboratories, see the spreadsheet of MassDEP Certified Laboratories that Test for Arsenic Speciation, below.
Where can I have my well water sample speciated for arsenic 3 and arsenic 5 concentrations?
Inorganic arsenic occurs naturally as arsenic 3 and arsenic 5. Arsenic 3 is significantly more difficult to remove from water than arsenic 5. Therefore, if the total arsenic concentration in your well water exceeds the public drinking water standard, you should consider having a sample tested for arsenic speciation in order to select a treatment option that will remove a sufficient amount of arsenic to produce finished water that meets the standard. See the list of MassDEP certified labs that test for arsenic and uranium (linked to the previous section).
Is my town included in the study area?
See the Town Maps listing, linked below, to determine whether there is arsenic or uranium probability information available for your town. If your town is listed, you will also find links to PDF maps of your town for arsenic and uranium probability zones.
Where can I find specific information about the probability of arsenic or uranium in my well water?
You may use the Well Locator Tool for Obtaining Arsenic and Uranium Probability Estimates to enter a street address and town name to obtain information regarding the probability that your bedrock well water may not meet the public drinking water standards for arsenic and uranium. Also, Town Maps showing the arsenic and uranium probability zones are available.
Both the well locator tool and the applicable town maps for uranium probability zones identify areas of bedrock that are mapped as granite or pegmatite that are located outside of the area covered in the USGS study. Although no probability statistics for the occurrence of uranium is available for these specific granite or pegmatite units, bedrock wells in these types of rock generally have an increased chance of containing naturally occurring radon, radium, and uranium concentrations exceeding the drinking water limits.
What kind of treatment should I install for removal of arsenic or uranium and how much will it cost?
There are typically two variations, or species, of inorganic arsenic in water: 'arsenic 3' and 'arsenic 5.' This is significant because 'arsenic 3' is very difficult to remove from water and must be changed or oxidized to 'arsenic 5' before it can be removed. Anion exchange, reverse osmosis, activated alumina, and other types of adsorptive media filters are most commonly used for arsenic removal. Depending upon whether you are treating only the water that goes to your kitchen sink or all of the water that enters your home, the median cost for the installation of arsenic removal systems is between $1,200 and $3,000 (not including the cost of pretreatment to convert 'arsenic 3' to 'arsenic 5,' which may or may not be required).
Reverse osmosis and anion exchange are most commonly used for uranium removal. Depending upon whether you are treating only the water that goes to your kitchen sink or all of the water that enters your home, the median cost for the installation of uranium removal systems is between $1,600 and $2,500.
Do I need to treat all of the water or just the water that goes to the kitchen sink faucet?
For those wells that exceed the arsenic and uranium drinking water standards in Massachusetts, the concentrations are typically only of concern for ingestion. Therefore, only treating the water that is used for drinking and cooking water is typically all that is required for protecting the health of your family. If your arsenic concentration exceeds 0.5 milligrams per liter (mg/L) (or 500 parts per billion), which is extremely rare in Massachusetts, then you should consider whole house treatment.
Can I discharge reject water from my reverse osmosis treatment system to my Title 5 septic system?
The answer depends upon the type of RO treatment system, the concentration of arsenic and uranium in the raw water and the use of the property. On-site discharges of RO reject water from Point-of-Use (POU) (i.e. treating only the water that flows to the kitchen sink) drinking water treatment devices at one- to four-unit residential properties may typically be discharged to a Title 5 septic system, but only if the following raw (untreated) water concentrations limits for arsenic and uranium are met:
- total arsenic concentration is less than 1 milligram per liter (mg/L) or 1 part per million (ppm) in the raw (untreated) water; and
- contact Joe Cerrutti or Steve Hallem (contact information provided at the end of this page) for information regarding allowable uranium concentrations in the raw water.
POU devices that are used at properties composed of greater than four residential units or are used for purposes other than residential use may not discharge to a Title 5 septic system. Point-of-Entry (POE) (i.e. treating all of the water that enters the house) drinking water treatment systems may not discharge to a Title 5 septic system. Wastewater from a drinking water treatment system that may not be discharged to the Title 5 septic system must either be discharged to a municipal wastewater treatment system or to separate dry well. The discharge to a dry well requires the submittal of a MassDEP Underground Injection Control (UIC) registration application with the exception of properties that are only used for one family residential unit.
Can I discharge arsenic or uranium wastewater from my drinking water treatment system to a dry well?
All discharges from water treatment systems require a MassDEP approved UIC registration, with the exception of properties that are only used for one family residential unit. See discussion for preceding question regarding exemption for certain reverse osmosis (RO) reject water for POU systems. In order to approve a UIC registration application for water treatment system discharges, MassDEP assesses whether the discharge has the potential to result in a violation of the drinking water standard in the receiving groundwater. Due to dilution effects, MassDEP may approve of discharges to a dry well that exceed the public drinking water standards, but there is no set limit and each application is considered on a case-by-case basis. MassDEP can not approve of any discharges of water in which arsenic exceeds the federal hazardous waste threshold (Toxicity Characteristic) of 5 milligrams per liter (mg/L) or 5 parts per million (ppm) or in which uranium exceeds 0.600 mg/L or 600 parts per billion (ppb). Contact Joe Cerutti or Steve Hallem (contact information provided at the end of the this page) for information regarding allowable uranium concentrations in the discharge to a UIC well.
Is there any funding available to low-income homeowners for installing a treatment system?
The US Department of Agriculture (USDA) Rural Development's Home Improvement and Repair Loans and Grants Program (Section 504) funding may be available to very low-income homeowners in qualifying communities. These loans or grants may be used by homeowners to address general repairs to improve or modernize, weatherize and/or remove code violations This program may be used for on-site water treatment systems, and hook-up costs to municipal systems that are necessary for the safe and sanitary condition of the dwelling. This program is available in rural communities and small-incorporated towns/cities of up to 10,000 population. Some communities of between 10,000 to 20,000 populations may be eligible. Homeowners should check the USDA Rural Development web site for eligibility requirements and for information on how to apply at: https://www.rd.usda.gov/ma.
Who regulates private wells?
Under Massachusetts General Law (MGL Ch.111 s.122), local Boards of Health (BOHs) have primary jurisdiction over the regulation of private wells. The local BOH is empowered to adopt a Private Well Regulation that establishes criteria for private well siting, construction, water quality and quantity.
What is the state doing about the problem?
MassDEP provided much of the funding of the USGS study that identified the high and low probability zones and MDPH provided the funding for a private well mapping study that was used in the USGS study and MDPH funded and conducted the urine analysis effort that was run concurrently with the USGS study.
MassDEP has developed a Well Locator Tool for Obtaining Arsenic and Uranium Probability Estimates to provide an easy way for private well owners to obtain additional information regarding the probability that their bedrock well water exceeds the public drinking water standards for arsenic and uranium.
MassDEP, MDPH, and USGS have provided and will continue to provide outreach to the local boards of health, informing them of the study results and where they can direct private well owners for additional information.
MassDEP has developed town-scale PDF maps of the arsenic and uranium probability zones and made them available to the general public and local boards of health for the towns for which USGS information exists regarding the probability that arsenic or uranium exceed public drinking water standards, or for which there are types of bedrock that are generally known to have an elevated probability of containing uranium and other radionuclides at concentrations exceeding public drinking water standards.
MDPH provides information regarding the health effects of arsenic and uranium to any private well owner seeking information.
MassDEP provides information regarding the available treatment technologies to any private well owner seeking information.
Please note that MassDEP does not regulate private drinking water wells.
Can my pet drink water that exceeds the drinking water standard for arsenic/uranium?
Different species of pets may have different sensitivities to arsenic and uranium in drinking water. However, it is recommended that pets be given drinking water that conforms to the same standards/guidelines set for humans.
Who can I contact for more information or questions?
If you have additional questions that are not answered by this document and the associated links, you may obtain additional information from the following:
For questions regarding the USGS report contact the USGS Water Science Center: https://www.usgs.gov/centers/new-england-water/connect
For questions regarding health effects of arsenic and uranium contact MDPH at 617-624-5757 or 800-240-4266.
For questions regarding arsenic treatment contact Joe Cerutti, MassDEP at 617-292-5859, email: firstname.lastname@example.org.
For questions regarding radiological treatment contact Steve Hallem, MassDEP at 617-292-5681, email: email@example.com.