Definition

Percent of tested private wells with arsenic concentration exceeding the maximum contaminant level of 5 micrograms of arsenic per liter

Numerator

Number of tested private wells with arsenic concentration exceeding the maximum contaminant level of 5 micrograms of arsenic per liter in a specified period of time

Denominator

Number of tested private wells in a specified period of time

Data Interpretation Issues

In January 2006, the maximum contaminant level (MCL) for arsenic in New Jersey was reduced from 50 micrograms per liter to 5 micrograms per liter.

Why Is This Important?

Arsenic is a naturally-occurring element in the earth's crust, and trace amounts can be found in geologic formations and aquifers in parts of New Jersey. Arsenic may also be found in soils as a result of past use of arsenic-containing pesticides and wood preservatives. Arsenic has been classified by the U.S. Environmental Protection Agency (USEPA) as a known human carcinogen. Ingestion of large amounts of inorganic arsenic is associated with increased risk of several types of cancer, including skin, lung, liver, kidney and urinary bladder. Other potential effects of ingesting large amounts of arsenic include diarrhea, thickening and/or discoloration of the skin, diabetes, and heart disease.

How Are We Doing?

Between 2002 and 2018, about 8.3% of 49,404 private wells in New Jersey that were tested for arsenic exceeded the state MCL of 5 micrograms per liter. Arsenic standard exceedances were most commonly found in Mercer (18.2% of wells), Somerset (16.8% of wells), Hunterdon (16.3% of wells), Essex (13.1% of wells) and Bergen (10.2% of wells) Counties. Online maps showing detection of arsenic 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 Department of Environmental Protection (NJDEP) adopted a new maximum contaminant level (MCL) for arsenic of 5 micrograms per liter, effective in January 2006, giving New Jersey the most protective arsenic standard in the nation. The MCL for arsenic in the U.S. is 10 micrograms per liter. The New Jersey Private Well Testing Act (PWTA) became effective in September 2002. The PWTA requires the buyer or the seller of real property to test well water prior to sale and review the results prior to closing of title. It also requires landlords to test the private well water supplied to their tenants and provide their tenants with a written copy of the results. Test results are provided to homeowners by the laboratory performing the analyses and are also sent to the New Jersey Department of Environmental Protection (NJDEP). The NJDEP notifies the local health agency when a well within its 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. Arsenic was initially required to be tested for in private wells in only 12 of New Jersey's 21 counties. These counties were selected due to the higher likelihood of finding arsenic. Testing for arsenic was added in two counties (Sussex and Warren) beginning in March 2008 and testing for arsenic is now required in all NJ counties.