Uranium is a naturally-occurring metallic mineral that can turn up in both ground water and surface water in areas where it exists in the local bedrock.  It is radioactive and toxic to life at high exposures.  It has been linked to various cancers, including bone cancer, and is toxic to the kidneys.

Naturally-occurring uranium takes three forms (also known as isotopes): uranium-234, uranium-235, and uranium-238. Uranium-238 is the most common form. Over 99 percent of the uranium found in nature is uranium-238.

Uranium is not stable but breaks down into other elements including radium and radon. This process is called decay, and alpha radiation is released. Both radium and radon are also unstable, and decay to other elements, releasing additional radiation. Together, all of these various forms of radiation-emitting breakdown products are called radionuclides.  The total amount of radioactivity emitted is combined and often referred to as gross alpha. The gross alpha results are measured using the term pico Curies per liter (pCi/l).

Uranium used in the nuclear industry and in weapons manufacture has been enriched to increase its propensity for nuclear fission.  Enriched uranium does not occur naturally in the environment, but may be present in the case of industrial accident or downwind of nuclear explosions.

Drinking Water and Radionuclide Testing

The Federal Safe Drinking Water Act requires that community water systems perform testing for radionuclides.

In Maine, new public water systems must test for gross alpha and radon to fulfill this mandate.  A high gross alpha result may instigate further testing to isolate the source of radioactivity, such a testing for uranium.

 

Exposure Limits:

Uranium

Maine Maximum Exposure Guideline (MEG) limit: 30 ug/L   (= 30 ppb)

USA Primary Drinking Water Standard limit : 30 ug/L

Other Radionuclides and Gross Alpha Radiation

Contaminant Maxium Contaminant Level - GOAL (mg/L) Current Maximum Contaminant Level (mg/L) Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) Sources of Contaminant in Drinking Water
Alpha particles zero 15 picocuries per Liter (pCi/L) Increased risk of cancer Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation
Beta particles and photon emitters zero 4 millirems per year Increased risk of cancer Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation
Radium 226 and Radium 228 (combined) zero 5 pCi/L Increased risk of cancer Erosion of natural deposits
Uranium zero 30 ug/L as of 12/08/03 Increased risk of cancer, kidney toxicity Erosion of natural deposits

Resources:

Wikipedia: Uranium

Maine Drinking Water Program, "Radionuclides" (webpage)

State of Connecticut Fact Sheet, "Uranium in Private Well Water" (2016, 2 pg. pdf)

US EPA, "Radionuclides Rule": https://www.epa.gov/dwreginfo/radionuclides-rule

US EPA, "Alpha Particles"

Test Methods for Uranium*

Drinking Water – EPA 200.8 (SDWA Compliant)
Wastewater – EPA 200.8 (NPDES Compliant)
Solids – EPA 6020A (SW846) (RCRA Compliant)

Sample Requirements

Drinking Water

Container: plastic, glass
Volume: 125 mL
Hold Time: 6 months if preserved with HNO3 to pH<2, otherwise 2 weeks
Preservation: HNO3 to pH<2

Wastewater:

Container: plastic, glass
Volume: 125 mL
Hold Time: 6 months if preserved with HNO3 to pH<2, otherwise 2 weeks
Preservation: HNO3 to pH<2

Solids:

Container: plastic, glass
Volume: a least 150g
Hold Time: 6 months
Preservation: n/a

Test Methods for Gross Alpha*

Drinking Water – EPA 900.0  (SDWA Compliant)
Wastewater – N/A  (NPDES Compliant)
Solids – N/A (SW846) (RCRA Compliant)

Sample Requirements for Gross Alpha

Drinking Water 

Container: Plastic
Volume: 1 L
Hold Time: 6 Months
Preservation: Nitric Acid pH <2 within 5 days of collection

Wastewater: n/a
Solids: n/a

*MEL sub-contracts these tests to another lab