Gill, I'd bet that San Saba caves could could have slightly higher radon than background, especially if they are connected to groundwater enriched in radon and have little air turnover. Radon gas is denser than air.
You'd need long term exposure for it to be a health risk. Living in a poorly ventilated house with a water well producing from igneous, metamorphic or coal or hcarb-bearing strata would be of much greater concern naturally. Most of Texas (including San Saba), has very low radon gas compared to many other parts of the country. Risk increases over the Llano Uplift and El Paso area. See map. http://www.city-data.com/radon-zones/Texas/Texas.html The ash layers (bentonite beds) in our local Austin Chalk are somewhat radioative. Recent studies of groundwater from Houston have shown elevated levels (above EPA MCLs) of uranium and radium. Tangentially, no level of radioativity is really safe but avoiding cigarretts, air travel and x-ray machines is helpful. Aimee ________________________________ From: Gill Edigar <[email protected]> To: Cavers Texas <[email protected]> Sent: Tue, December 21, 2010 5:18:05 PM Subject: [Texascavers] San Saba County/CO2/radon For a long time after I first visited caves in San Saba County in the 1960s I assumed that the source of the high levels of CO2 were due to decomposition of organic materials that originated on the surface. At some point (years ago) after radon became a hot topic I started associating radon with CO2 out gassing and more recently wondering if any radon studies have been done at CBSP. So I asked my caver friend and geologist Steve Hall of Virginia about those relationships. He is a radon specialist. He said that the source of out gassing CO2 is often igneous rocks which are also a radon source. I started to wonder what the rock sequence was in the Gorman Falls area. How thick is the limestone/dolomite? What formations lay between the top layer and the granite below? Could that be a source for the CO2? Should cavers there take any special precautions regarding radon? I tried the internet without getting much satisfaction so am wondering if anybody has information on any of that handy. It would make an interesting discussion. --Ediger --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
