Radon is released with methane during the extraction process of hydrofracking. This is true wherever fracking is done. The shale and gas in the Marcellus areas of Pennsylvania has proven to be more highly radioactive than other, more distant shale plays, which have previously supplied New York’s gas. Radon is more of a concern the closer the supply, because there is less time for the radioactivity to dissipate. It is estimated that gas from Pennsylvania would travel to NYC within one day’s time. During winter months, when demand is higher, gas is delivered faster, and, with apartment windows tending to be closed, the risk would be even greater.
And this does not take into account the fact that there are 7 other isotopes after the radon that are radioactive before reaching the stable isotope of lead, Pb-206. Each of these is the result of a monoatomic radon. Individual atoms of even heavy metals can remain suspended in a gas for extended periods or get blown around as dust. And remember, lead is toxic and causes mental retardation at any age, but especially in children. It has been banned as a fuel additive for this reason and in shotgun pellets for waterfowl hunting.