Typically urban air holds .000007 mg mercury per cubic meter writes Nucon in selling their Mersorb Mercury absorbing product. Locations in South Texas have shown Mercury concentrations in NATURAL GAS ranging from 0.002 mg/m3 to over 4.5 mg/m3. “The Threshold Limit Values-Time Weighted Average (TLV-TWA), established by AIGCH, is 0.05 mg mercury per cubic meter air.”
And as for OFFSHORE drilling, contributors of Mercury in our seafood read here…..http://usa.oceana.org/impacts-offshore-drilling “Drilling muds and produced water are disposed of daily by offshore rigs. Offshore rigs can dump tons of drilling fluid, metal cuttings, including toxic metals, such as lead chromium and mercury, as well as carcinogens, such as benzene, into the ocean”.
ADDITIONALLY the “….process of flaring involves the burning off of fossil fuels which produces black carbon. Black carbon contributes to climate change as it is a potent warmer both in the atmosphere and when deposited on snow and ice. Drilling activity around oil rigs is suspected of contributing to elevated levels of mercury in Gulf of Mexico fish”.