Definition

Percent of tested private wells with gross alpha exceeding the maximum contaminant level of 15 picoCuries per liter(pCi/l)

Numerator

Number of tested private wells with gross alpha concentration exceeding the maximum contaminant level of 15 pCi/l in a specified period of time

Denominator

Number of tested private wells in a specified period of time

Data Interpretation Issues

Gross alpha particle activity is a surrogate measurement for radium and is a measurement of all alpha radioactivity present, regardless of the specific radionuclide source. The federal maximum contaminant level (MCL) for gross alpha is 15 pCi/l minus the contribution from uranium. Initially, nine southern New Jersey counties in the Coastal Plain (Atlantic, Burlington, Camden, Cape May, Cumberland, Gloucester, Monmouth, Ocean, and Salem) and three northern counties (Hunterdon, Mercer, and Middlesex) were required to monitor for gross alpha. In the Coastal Plain, where the only radionuclide present is radium, this surrogate test works well. However, outside of the Coastal Plain, groundwater samples may contain uranium, radium, or a combination of both. Both elements emit alpha radioactivity and so gross alpha measurements do not provide sufficient information to determine whether a particular sample exceeds the drinking water MCL. Currently, testing for gross alpha is required in all 21 NJ counties. Of all of the private wells sampled statewide, 10.9 percent contained gross alpha levels above the federal MCL.

Why Is This Important?

Gross Alpha is a test that is performed to measure the overall radioactivity in drinking water. Naturally occurring radioactive elements emit alpha particles as they decay. Alpha radiation exists in soil, air, and water. Sampling of public and private wells that draw water from southern New Jersey's Cohansey aquifer has shown elevated levels of naturally occurring radioactivity. Exposure to radium over a long period of time is believed to increase one's lifetime risk of developing certain types of cancer.

How Are We Doing?

Between September 2002 and December 2018, 10.9% of 64,846 private wells in New Jersey tested for gross alpha exceeded the MCL of 15 pCi/l. Gross alpha exceedances were most commonly found in Camden (35.6% of wells), Cumberland (29.9% of wells), Salem (17.2% of wells), and Sussex (15.1% of wells) Counties. Online maps showing gross alpha exceedances are available at the county level, municipal level, and for 2 mile by 2 mile grids from NJDEP, [http://arcg.is/1CPkHyC].

What Is Being Done?

The New Jersey Private Well Testing Act (N.J.S.A. 58:12A-26 et seq.) became effective in September 2002. The PWTA requires the buyer or the seller of a property to test untreated well water prior to the sale and review the results prior the closing of title. It also requires landlords to test the private well water supplied to their tenants every five years and provide their tenants with a written copy of the results. The data generated by this program are provided to the homeowners by the laboratory performing the analyses and then sent to the New Jersey Department of Environmental Protection (NJDEP). The NJDEP notifies local health agencies when a well within their jurisdiction is tested under the PWTA. The data from the PWTA are used by NJDEP to assess the quality of the water from private wells throughout the state.