In this post I attempt to provide a context for an article in NYT, Drilling Down: Regulation Lax as Gas Wells’ Tainted Water Hits Rivers by IAN URBINA, published on February 26, 2011. The article seems to imply that much of the potentially deadly radioactive contamination of drinking water supply in Pennsylvania comes from "frac water" produced after hydrofracturing the deep natural gas wells there. Such an assertion is not supported by facts, and here is why.
The raw data from the NYT spreadsheet, emailed to me by Mr. Urbina, are plotted here. In the spreadsheet, there are up to five different measurements of radioactivity in the water produced from each of 212 natural gas wells in Pennsylvania. Total alpha radiation refers to all alpha-particle-emitting radioisotopes present in the produced water. In some wells there were additional measurements of alpha-radioactivity from two isotopes of radium and two isotopes of uranium. By subtraction, the difference of between the total alpha radioactivity and those of the other radio-isotopes can be attributed mostly to radon.
Drinking groundwater can have trace quantities of dozens of the naturally occurring radioactive elements. Radon 222 is a ubiquitous naturally occurring radioactive gas that is water-soluble. Radon's decay in air or water is measured in picocuries per liter (pCi/L). The fast-decaying radon is produced during radioactive decay of uranium 238 and thorium 232 that have been in the earth's crust since the earth was formed.
A picocurie per liter is 0.037 radon atoms giving out radiation in one second in one liter of water, or 1 atom of radon giving out radiation in 1 second in 27 liters of water. The U.S. Environmental Protection Agency (EPA) estimates that 10,000 pCi/L of radon in water translates to about 1 pCi/L of radon in air.
The maximum total alpha-particle (mostly from radon, but in some wells also from radium-226 and -228, and uranium- 235 and -238) emissions measured in water produced from two natural gas wells in Pennsylvania were 32,360 pCi/L and 40,880 pCi/L, respectively. I will address the much smaller radium and uranium radioactivity in the produced water and the dilution factors in a later post.
The current "action level" for airborne radon is 4 pCi/L. The EPA recommends that action be taken to lower airborne radon if it exceeds 4 pCi/L in your home. While there are no EPA standards for radon in water now, a maximum contaminant level (MCL) of 300 pCi/L and an Alternative Maximum Contaminant Level (AMCL) of 4,000 pCi/L for public water supplies have been proposed.
Water directly out of the tap contains about 0.01 pCi/L each of uranium, radium, and radioactive lead. It may also contain between 100 and 400 pCi/L of radioactive hydrogen, between 100 and 500 pCi/L of radioactive carbon, between 10 and 30 pCi/L of radioactive beryllium, as well as a variety of other radioactive elements such as aluminum, chlorine, silicon, lead, bismuth, polonium, and argon. It can contain several hundred to several thousand pCi/L of radon gas, particularly if you get your drinking water from a well.
We have about 120,000 picocuries of radioactivity in our bodies from all sources. These naturally-occurring radioactive substances expose our bodies to about 25 "millirem" per year, abbreviated as "mrem/yr". (Millirem measures energy of radiation, like heat.) If you live in Denver, you are exposed to 50 millirems per year. A single CT-scan test exposes you to up to 1,000 mrems of radiation. CT radiation alone contributes 1/4 of U.S. population's radiation exposure!
Public groundwater supplies seem to have the highest radon levels in places where the water flows through granites in the Piedmont. (The Piedmont is a plateau region located in the eastern United States between the Atlantic Coastal Plain and the main Appalachian Mountains, stretching from New Jersey and Pennsylvania in the north to central Alabama in the south.)
The highest readings there have been well over 10,000 pCi/L. The lowest concentrations occur in the coastal plain region, where many readings are below 100 pCi/L. Concentrations from about 500 to 10,000 pCi/L occur in groundwater water samples drawn from metamorphic rocks, such as the gneisses and schists found in the piedmont and mountain regions. Both types of rock are used as building materials.
In conclusion, the two highest radon concentrations measured in frac water back-produced from natural gas wells in Pennsylvania are in line with some groundwater samples in the region.
A high concentration of radon in the groundwater in your area does not necessarily mean that there will be a high concentration of radon in your drinking water. Radon escapes harmlessly into the air when water is being treated for use in a municipal system. Also, radon decays into other substances over time while the water is being stored. Municipal systems that mix surface water—a lake or a river—with groundwater will have lower waterborne radon levels.
High levels of waterborne radon tend to occur in homes on an individual well or a community well system (serving up to about 100 homes) if the groundwater has a high level of radon. However, a private groundwater well should not receive the produced frac water.
Based on a second 1999 NAS report on radon in drinking water, EPA estimates that radon in drinking water causes about 168 cancer deaths per year, 89 percent from lung cancer caused by breathing in radon released from water, and 11 percent from stomach cancer caused by drinking radon-containing water.
The Centers for Disease Control and Prevention (CDC) estimated 52,447 deliberate and 23,237 accidental non-fatal gunshot injuries in the United States during the year 2000. The majority of gun-related deaths in the United States are suicides, with firearms used in 16,907 suicides in the United States during 2004. Thus, an average U.S. resident is almost 1,000 times more likely to shoot him/herself with a gun, than die from stomach cancer caused by drinking radon-contaminated water. By the way, each year there are about 150,000 lung-cancer deaths the U.S. (157,300 in 2010). It is estimated that about 21,000 of the lung-cancer deaths are caused by breathing airborne radon that seeps into our homes from soil. CT scans alone might lead to 29,000 new cancer cases in the U.S.
In 1994 there were 41,000 deaths in traffic accidents, down to 34,000 in 2009. In 2007, CDC reported 182,479 deaths and injuries due to accidents in the U.S., including 18,773 homicides and law enforcement-related deaths.
In 1994 there were 41,000 deaths in traffic accidents, down to 34,000 in 2009. In 2007, CDC reported 182,479 deaths and injuries due to accidents in the U.S., including 18,773 homicides and law enforcement-related deaths.
So, please, pick your risks wisely. Otherwise, you will be frightened and distracted by a mere scary-cat. Instead, you should be watching for a brick falling directly onto your head.
Tad:
ReplyDeleteThe EPA appears to have a standard for gross alpha of 15pCi/L here. Based on that standard, the NYT would appear to be correct that some of the frac wastewater is thousands of times over the drinking water limit.