PHILADELPHIA, July 1 (Reuters) - Officials have quarantined 28 cows that may have drunk toxic waste water from natural gas drilling in Pennsylvania, adding to concerns about health risks arising from exploiting the state's vast shale deposits.
The cows had access for at least three days to a pool that formed from a leaking waste water holding pond on a farm in Tioga County, north-central Pennsylvania, where East Resources Inc (EOG.N) is drilling into the Marcellus Shale formation.
The state agriculture department said on Thursday that the toxic water may have contaminated the cows' meat and that they were quarantined on May 1.
Some of the state's farmers have reported cases of sick animals and birth malformations that they blame on toxic chemicals used in hydraulic fracturing ("fracking"), which energy companies use to draw gas from deep deposits.
Waste water from the gas drilling process contains chemicals injected into the ground to fracture the gas-bearing rock, as well as naturally occurring toxic substances that are disturbed deep underground during fracking and drilling.
Pennsylvania is estimated to have enough gas in its Marcellus Shale formation to meet total U.S. needs for a decade or more and is drawing the attention of major energy companies as well as groups concerned about possible health risks.
It was the first time the state has quarantined cattle related to natural gas drilling in Pennsylvania, said Justin Fleming, a spokesman for the Agriculture Department.
Tests found the water contained chemicals including chloride, magnesium, potassium, and strontium, the department said in a statement. Strontium, a heavy metal, is of particular concern because it can be toxic to humans, especially children, officials said.
"We took this precaution in order to protect the public from consuming any of this potentially contaminated product," said Agriculture Secretary Russell Redding.
No cows were seen drinking the waste water but tracks were found throughout the pool, and grass was dead in a roughly 30-foot by 40-foot (10-metre by 13-metre) area around it, the statement said.
There are 20 adult cows, which will be held from the food chain for six months, and eight calves which will be removed from the food chain for two years.
The safety concerns grew after a June 3 incident in which another Pennsylvania well operated by EOG Resources experienced the first blowout in the current drilling boom, spewing gas and fracking fluid into the surrounding area for 16 hours. (Editing by David Storey)