The Agency for Toxic Substances and Disease Registry (ATSDR) investigated the water quality of seven residential wells surrounding the Chesapeake ATGAS 2H natural gas well site in Leroy Township, Bradford County, Pa., at the request of the U. S. Environmental Protection Agency (EPA) following a well blowout. ATSDR found that several wells had elevated levels of salts and other chemicals, according to a report released today. While it is unclear how the wells were contaminated, the available data suggest to ATSDR that one well was impacted by natural gas activities. The data from the other six wells did not suggest impact from natural gas activities.

ATSDR evaluated groundwater data from the wells after a well head, the structure at the surface of an oil or gas well, failed and released fluids and combustible gases. The gases, including methane, escaped into the atmosphere. Initially, the vapors posed a risk for an explosion; however, after Chesapeake Energy Corporation stabilized the well (about five days after the release), the explosive vapor levels were no longer detected.

To read the public health consultation, please visit: http://www.atsdr.cdc.gov/HAC/pha/ChesapeakeATGASWellSite/ChesapeakeATGASWellSiteHC10282013_508.pdf

ATSDR's public health consultation reported, based on EPA samples collected from the seven wells in April 2011:

• One of the seven wells, Well No. 4, showed a 10-fold increase in methane and various salts, compared with samples taken in July 2010, before natural gas drilling began at the site. These chemicals are consistent with those expected to be mobilized from natural gas extraction activities. Adults and children drinking water from this well would exceed the recommended daily dietary guidelines for sodium. Lithium was detected at a level exceeding the EPA screening level. The lithium level could be of concern to people currently undergoing lithium therapy or taking certain drugs that interact with lithium. The reason for the change in chemical levels in Well No. 4 between pre- and post-blowout sampling is unclear. Further evaluation at the site is needed to understand the source of the impacts to Well No. 4.

Although findings from the other six wells do not suggest an impact from natural gas drilling or related activities, the sampling results showed some well water chemicals at levels of health concern.

• Consuming water from six of the seven wells at this site with elevated sodium levels (wells No. 2, 3, 4, 5, 6, and 7) may be of health concern to people on sodium-restricted diets. However, based on the maximum concentrations measured from these seven private wells, it is unlikely that healthy children or adults would be exposed to individual levels of inorganic salts, such as barium, calcium, magnesium, manganese, and/or potassium, at levels that would result in adverse health effects.
• Arsenic was detected in all seven wells. In five wells, levels were below reporting limits. In Well No. 2, the highest finding, of 30 micrograms per liter, would add a small additional cancer risk (6 in 10,000) for people drinking the water every day for 30 years. The level of arsenic in Well No. 2 is similar to the level found in the samples taken in July 2010 before natural gas well drilling and/or completion activities began. Adults are unlikely to experience non-cancer health effects at this level of exposure. Children who drink one liter of water containing 30 micrograms per liter every day over a year could be at increased risk of non-cancer health effects. Arsenic can affect the skin, liver, digestive and nervous systems. Some arsenic is natural in groundwater in this part of the country.
• Well No. 3 showed detectable levels of gross alpha radiation, a measure of radioactivity in drinking water. Radioactive substances occur naturally in groundwater. The Marcellus Shale is considered to have elevated levels of naturally occurring radioactive material. Based on the sampling information available, the level of alpha radiation detected in Well No. 3 would not produce adverse health effects.

Residents were given detailed, in-person explanations of findings in their wells by EPA and ATSDR. Residents drinking water from Wells No. 2, 3, and 4 are being provided bottled or treated water by EPA or Chesapeake Energy Corp. The permanent treatment systems should make water in two of the wells safe to drink, assuming these systems are properly maintained. Bottled water will continue to be provided to the owners of Well No. 3 until further evaluation of the radiation levels in this well are complete.

The Pennsylvania Department of Environmental Protection (PADEP) provided supplementary groundwater sampling results for this site that were shared with ATSDR, and the Pennsylvania Department of Health (PADOH) provided technical review of ATSDR's public health evaluation for this site. ATSDR is sharing the results of this evaluation with state and local agency partners.

The ability to reach definitive conclusions is limited by the data available to ATSDR at this time. In order to reach more definitive conclusions, long term assessments should be undertaken, which could include:

• Studying potential health effects from exposure to chemicals released or mobilized by natural gas activities into the air, water, soil, plants and animals, and potential differences in different parts of the country;
• Testing of residential drinking water wells before, during and after natural gas activities.

The EPA is conducting further investigations in the area as part of the Agency's larger study on hydraulic fracturing. As conditions warrant, ATSDR will continue to work with EPA and relevant state agencies to monitor and analyze findings.

Editor's Note: The Agency for Toxic Substance and Disease Registry, ATSDR, is a federal public health agency of the U.S. Department of Health and Human Services. It is commonly referred to as CDC's sister agency.

Its mission is to prevent harmful exposures and diseases related to toxic substances.

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U.S. Department of Health and Human Services