Radon
Status: No national drinking water standard exists
Radon is a radioactive gas that comes from soil and groundwater, and causes lung cancer. Highest exposures come from radon entering a house through its basement or crawl spaces, or from it volatilizing in the water. Read More.
Radon is the most common source of radiation exposure in the home. Radon in tap water is a smaller source of exposure compared to radon in indoor air. Water utilities report radon in picocuries per liter (pCi/L), which is a measure of radioactivity in water. The federal government has not set a Maximum Contaminant Level (MCL) for radon in tap water. In 1991, the EPA proposed a drinking water standard of 300 picocuries per liter for radon, which was not finalized. In 1999, the EPA proposed a combined approach for reducing radon risk in indoor air and limiting radon in drinking water. This approach recommended a maximum of 4,000 picocuries of radon per liter of drinking water in states with programs to address radon air risks. Where there was no state program for radon mitigation, a water radon limit of 300 picocuries per liter was to apply. This proposal has not yet become a federal law.
Click here to read more on radiological contaminants.
The draft federal limits for radon do not sufficiently protect public health. The EPA’s analysis on radon cancer risk suggests that for a water limit of 300 picocuries per liter, 200 in every 1 million people drinking water with this much radon could develop cancer over their lifetimes. For a water limit of 4000 picocuries per liter, over 2,000 people in every 1 million could develop cancer over their lifetimes. The EPA estimates that radon in drinking water causes about 168 cancer deaths per year – nearly 90 percent of which come from lung cancer caused by breathing radon released from water during showering or other water use. The remainder of cancer deaths are primarily from stomach cancer caused by consuming radon in water.
2014-2019:
19
states detected
357
utilities detected
5.9 million
people served
19
states over health guideline
361
utilities over health guideline
5.9 million
people served over health guideline
Health concerns for radon
Lung cancer
Stomach cancer
State and national drinking water standards and health guidelines
EWG Health Guideline 1.5 pCi/L
The EWG Health Guideline of 1.5 pCi/L for radon was defined by the Environmental Protection Agency as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.
pCi/L = picocuries per liter
States reporting radon in drinking water
| UTILITIES REPORTING ABOVE HEALTH GUIDELINES | UTILITIES WITH CONTAMINATION | ||||||
|---|---|---|---|---|---|---|---|
| State | Utilities | People Served | Utilities | People Served | |||
| California | 64 | 2,270,441 | 64 | 2,270,441 | |||
| New York | 15 | 1,160,892 | 17 | 1,161,882 | |||
| Arizona | 5 | 562,763 | 5 | 562,763 | |||
| Wisconsin | 47 | 450,555 | 47 | 450,555 | |||
| Missouri | 22 | 337,044 | 15 | 334,674 | |||
| Oregon | 3 | 248,909 | 3 | 248,909 | |||
| Washington | 5 | 240,523 | 5 | 240,523 | |||
| Nevada | 58 | 209,895 | 59 | 209,959 | |||
| Maryland | 27 | 102,223 | 27 | 102,223 | |||
| Massachusetts | 28 | 72,712 | 28 | 72,712 | |||
| Utah | 3 | 63,692 | 3 | 63,692 | |||
| Maine | 59 | 48,787 | 59 | 48,787 | |||
| Rhode Island | 3 | 48,132 | 3 | 48,132 | |||
| New Jersey | 1 | 14,000 | 1 | 14,000 | |||
| Pennsylvania | 1 | 12,800 | 1 | 12,800 | |||
| New Hampshire | 14 | 5,575 | 14 | 5,575 | |||
| West Virginia | 2 | 1,943 | 2 | 1,943 | |||
| Montana | 1 | 300 | 1 | 300 | |||
| Vermont | 3 | 211 | 3 | 211 | |||
Filtering technologies that reduce radon
Activated Carbon
Reverse Osmosis
Utilities with the highest amounts of radon, 2014-2019
| Utility | Location | Tests | Average level | People served |
|---|---|---|---|---|
| Staffordshire Country Estates | Leicester, MA | 21 of 22 | 28,598.95 pCi/L | 140 |
| Spinsfield Commons | Franklin, ME | 1 of 1 | 19,200.00 pCi/L | 45 |
| East Ridge Mobile Home Park | Waldoboro, ME | 14 of 14 | 19,182.86 pCi/L | 63 |
| Buffumville Heights Estates Condominium | Oxford, MA | 25 of 25 | 17,702.40 pCi/L | 40 |
| White Mountain Resort/gateway | Moultonborough, NH | 1 of 1 | 14,000.00 pCi/L | 208 |
| Northeastern Estates | Standish, ME | 7 of 7 | 13,961.86 pCi/L | 40 |
| Cherry Valley/ Rochdale Water District | Leicester, MA | 6 of 6 | 13,181.67 pCi/L | 3,337 |
| Pinewood On The Green Condos | Oxford, MA | 15 of 18 | 12,760.00 pCi/L | 50 |
| Fcwwd #40/shaver Springs | Fresno, CA | 2 of 2 | 12,440.00 pCi/L | 69 |
| Brandywine | Epping, NH | 1 of 1 | 12,200.00 pCi/L | 72 |
| Harriman Village | Harriman, NY | 4 of 4 | 11,439.45 pCi/L | 5,000 |
| Colby Waterworks | Colby, WI | 1 of 1 | 10,819.00 pCi/L | 1,829 |
| Charlton Manor Rest Home | Charlton, MA | 11 of 11 | 10,204.55 pCi/L | 26 |
| Countryside Apartments | Hollis, ME | 3 of 5 | 8,298.80 pCi/L | 32 |
| Benchmark Condominiums | Tyngsborough, MA | 12 of 18 | 6,346.67 pCi/L | 60 |
| Rockwood Meadows | Upton, MA | 23 of 23 | 6,115.57 pCi/L | 80 |
| Poland Place Condo Association | Poland, ME | 5 of 8 | 6,021.88 pCi/L | 35 |
| Togus Pond Mobile Home Park | Ventura, ME | 8 of 8 | 5,836.50 pCi/L | 53 |
| Saco River Apartments | Hollis, ME | 4 of 4 | 5,603.50 pCi/L | 30 |
| Ayer Road Properties LLC | Harvard, MA | 33 of 35 | 5,557.60 pCi/L | 150 |
| Lamoille Water Users Association | Lamoille, NV | 4 of 4 | 5,200.20 pCi/L | 200 |
| Chimera Inc. | Narragansett, RI | 1 of 1 | 4,600.00 pCi/L | 133 |
| Wiggin Farm Winterberry | Merrimack, NH | 1 of 1 | 4,321.00 pCi/L | 108 |
| Oliverian Sch | Haverhill, NH | 1 of 1 | 4,208.00 pCi/L | 76 |
| Buena Vista Apartments | Liberty, NY | 1 of 1 | 3,909.00 pCi/L | 52 |
| Brook Hollow | Portland, ME | 6 of 7 | 3,873.29 pCi/L | 30 |
| Bridgton Water District | Bridgton, ME | 14 of 14 | 3,636.29 pCi/L | 2,283 |
| Estates At Highland Ridge | Hopkinton, MA | 13 of 13 | 3,437.69 pCi/L | 100 |
| Country View Holdings Llc | Somerset, WI | 1 of 1 | 3,400.00 pCi/L | 75 |
| Sunrise Hill Estates | Barrington, ME | 1 of 1 | 3,180.00 pCi/L | 100 |
| Northbrook Village I / Berlin Ret. | Berlin, MA | 1 of 1 | 3,080.00 pCi/L | 48 |
| Leicester Water Supply District* | Leicester, MA | 4 of 6 | 2,764.57 pCi/L | 3,200 |
| Maine Water Company Kezar Falls Division | Saco, ME | 1 of 1 | 2,760.00 pCi/L | 993 |
| Fields At Sherborn Condo Trust | Sherborn, MA | 2 of 2 | 2,700.00 pCi/L | 110 |
| Canton Point Park | Hartford, ME | 6 of 6 | 2,656.82 pCi/L | 88 |
| Pawling Water District #1 | Pawling, NY | 4 of 4 | 2,495.00 pCi/L | 100 |
| Pawling Village* | Pawling, NY | 4 of 4 | 2,495.00 pCi/L | 2,200 |
| Old Coach Village | Derry, NH | 4 of 4 | 2,447.50 pCi/L | 50 |
| Northbrook Village II | Berlin, MA | 1 of 1 | 2,440.00 pCi/L | 80 |
| Regency At Stow Condominiums | Stow, MA | 2 of 2 | 2,395.00 pCi/L | 132 |
| Begin Trailer Park | Sabattus, ME | 1 of 1 | 2,380.00 pCi/L | 170 |
| Lynns Way | Skowhegan, ME | 1 of 1 | 2,350.00 pCi/L | 40 |
| Sunset Ridge Condominiums | Bolton, MA | 6 of 10 | 2,314.00 pCi/L | 42 |
| Mount Rose Bowl Property Owners Water Co. | Reno, NV | 1 of 1 | 2,307.20 pCi/L | 40 |
| Four Winds Homeowners Association | South Thomaston, ME | 1 of 1 | 2,238.00 pCi/L | 43 |
| Pilot Grove Apartments II | Stow, MA | 1 of 1 | 2,220.00 pCi/L | 134 |
| Stratham Woods | Stratham, NH | 1 of 1 | 2,153.00 pCi/L | 38 |
| Quakertown Boro | Quakertown, PA | 14 of 14 | 2,043.50 pCi/L | 12,800 |
| Freedom Village Condos | Nashua, NH | 1 of 1 | 2,043.00 pCi/L | 165 |
| Charter Oaks Village Cooperative | Waldoboro, ME | 22 of 23 | 2,024.57 pCi/L | 105 |
* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Radon, but it likely has the contaminant in its water supply.
| Utility | Location | Tests | Average level | People served |
|---|---|---|---|---|
| Quakertown Boro | Quakertown, PA | 14 of 14 | 2,043.50 pCi/L | 12,800 |
| Holliston Water Department | Holliston, MA | 1 of 1 | 1,900.00 pCi/L | 14,946 |
| Carson City Public Works* | Carson City, NV | 2 of 2 | 1,590.00 pCi/L | 56,000 |
| Maynard DPW, Water Division | Maynard, MA | 6 of 8 | 1,373.75 pCi/L | 10,665 |
| Westerly Water Department | Westerly, RI | 15 of 15 | 1,239.47 pCi/L | 38,000 |
| Elsinore Valley Municipal Water District* | Lake Elsinore, CA | 15 of 15 | 948.47 pCi/L | 142,264 |
| Sanford Water District | Sanford, ME | 1 of 1 | 930.00 pCi/L | 14,025 |
| Beverly Hills Water Department | Beverly Hills, CA | 8 of 8 | 874.13 pCi/L | 44,290 |
| Greater Augusta Utility District | Augusta, ME | 2 of 2 | 859.00 pCi/L | 15,040 |
| Eau Claire Waterworks | Eau Claire, WI | 2 of 2 | 752.00 pCi/L | 66,060 |
| South Tahoe PUD - Main* | South Lake Tahoe, CA | 62 of 62 | 725.24 pCi/L | 29,500 |
| Dayton Valley Water System* | Dayton, NV | 7 of 7 | 716.36 pCi/L | 15,830 |
| City of Elko | Elko, NV | 7 of 7 | 621.52 pCi/L | 20,451 |
| City of Tualatin | Tualatin, OR | 1 of 1 | 601.00 pCi/L | 26,879 |
| City of Santa Barbara Water Department* | Santa Barbara, CA | 1 of 1 | 470.00 pCi/L | 92,371 |
| City of Riverside* | Riverside, CA | 3 of 3 | 460.00 pCi/L | 303,871 |
| Tualatin Valley Water District* | Beaverton, OR | 1 of 1 | 440.00 pCi/L | 222,000 |
| City of Spokane* | Spokane, WA | 10 of 10 | 411.70 pCi/L | 227,509 |
| Oak Park Water Service | Ventura, CA | 97 of 118 | 377.31 pCi/L | 12,200 |
| Cal American Water Company | Newbury Park, CA | 97 of 118 | 377.31 pCi/L | 61,206 |
| Thousand Oaks Water Department | Thousand Oaks, CA | 97 of 118 | 377.31 pCi/L | 50,000 |
| California Water Service Company - Westlake | San Jose, CA | 97 of 118 | 377.31 pCi/L | 19,451 |
| Fernley Public Works | Fernely, NV | 1 of 1 | 369.00 pCi/L | 19,790 |
| California Water Service (CWS) - Salinas | San Jose, CA | 1 of 1 | 320.00 pCi/L | 106,858 |
| Fond Du Lac Waterworks | Fond Du Lac, WI | 1 of 1 | 240.40 pCi/L | 42,000 |
| City of Mesa* | Mesa, AZ | 2 of 2 | 230.50 pCi/L | 466,000 |
| Virgin Valley Water District | Mesquite, NV | 2 of 2 | 185.40 pCi/L | 18,000 |
| Coachella Valley Water District: Cove Community* | Palm Desert, CA | 2 of 2 | 184.50 pCi/L | 198,544 |
| City of Avondale | Avondale, AZ | 17 of 18 | 178.36 pCi/L | 83,001 |
| Platteville Waterworks | Platteville, WI | 1 of 1 | 159.50 pCi/L | 12,268 |
| Patuxent Naval Air Station (NAVFAC-WASH) | Patuxent River, MD | 2 of 2 | 158.80 pCi/L | 22,000 |
| Madison Water Utility* | Madison, WI | 1 of 1 | 122.00 pCi/L | 235,000 |
| City of Westminster | Westminster, MD | 1 of 2 | 109.05 pCi/L | 35,256 |
| Sussex Village Hall & Water Utility | Sussex, WI | 1 of 1 | 99.20 pCi/L | 10,573 |
| Marin Municipal Water District* | Corte Madera, CA | 5 of 6 | 97.63 pCi/L | 195,362 |
| Independence* | Independence, MO | 2 of 2 | 77.35 pCi/L | 117,240 |
| Rockaway Twp Water Department | Rockaway, NJ | 1 of 1 | 50.00 pCi/L | 14,000 |
| St James WD | St James, NY | 4 of 4 | 21.62 pCi/L | 10,587 |
| Smithtown WD | Kings Park, NY | 4 of 4 | 21.62 pCi/L | 19,635 |
| Suffolk County Water Authority* | Bayshore, NY | 4 of 4 | 21.62 pCi/L | 1,100,000 |
* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Radon, but it likely has the contaminant in its water supply.