Gamma rays, alpha particles, and beta particles, which are given off by radioactive decay, have very different properties but are all ionizing radiation. Each form of ionizing radiations contains enough energy to break chemical bonds. The radiation can break bonds in DNA and RNA disrupting its function and potentially damage or destroy living cells. Alpha particles do not penetrate the skin but enter the body when alpha-emitters are in food, water, or air. While some beta particles are capable of penetrating the skin, beta emitters are more hazardous when they enter the body through food and water.
Radioactive elements are naturally present in rocks, soil, and water from trace amounts to dangerous concentrations depending on where you are. The occurrence of radionuclides in ground water is controlled primarily by the local geology and geochemistry of rock and the flow and age of the water. Research by the U.S. Geological Survey (USGS) found that the over time the concentration of a one radioactive element varied significantly from the same well. Migration and concentration of radionuclides depends on the amount of radioactive material in the bedrock, the moisture levels in the soil, groundwater circulation, and atmospheric pressure. Uranium, thorium, and radium can be highly mobile in groundwater and can move considerable distances and be re-deposited in soils or carried in the groundwater to the well. The isotopes of radium can enter the body through water, and some may be deposited in the bones and may over many years can result in an increased risk of getting cancer. Exposure to uranium in drinking water may result in toxic effects to the kidneys. Some people who drink water containing uranium over many years have an increased risk of getting cancer.
|Variation in Radon concentrations over time from USGS|
The EPA does not yet have a recommended drinking water standard for radon because the primary source of radon exposure is from breathing contaminated air in the home or office. EPA has focused on concentration of radon in the air. Radon is a colorless, odorless gas produced by the radioactive decay of radium, which in turn was formed by the decay of uranium. There is a correlation of elevated concentrations of radon in the inside air with elevated concentrations of radionuclidies in groundwater and groundwater can carry radon into the house.
Geological exploration has identified more than 55 locations within the Piedmont and Blue Ridge regions of Virginia where uranium is found. Uranium occurs in the Lovingston rock formation at a fraction of a percent, but radionuclides are known to be present in the groundwater in the regions thanks to sampling done at community water wells. About a decade ago, the USGS found that naturally occurring radionuclides in the ground water of southeastern Pennsylvania may pose a health hazard to some drinking water from wells drilled in the Chickies Quartzite. Counties in Maryland also have high radionuclides in water, just to name a few locations. You can find out more about the likelihood of radionuclides in your groundwater by inquiring at your state’s department of environmental quality or protection or by reading the community disclosure of nearby community water supply wells. That’s how I found out about local water quality and what to test for when I moved to this region.
If you are one of the 15% of U.S. households who obtain your water from a private well, you need to test your well. Every year you should test your well for bacteria and every few years for other substances including radionuclides. The radionuclides tests are expensive the cheapest way to go is to have a state and federal qualified and certified laboratory sample your well water for short-term GAPA, and GBPA. This screening test is less expensive than direct analysis for specific radionuclides. Testing for GAPA and GBPA may cost between $100 and $200, while testing for radium isotopes may cost between $200 and $300. Testing for total uranium may cost between $100 and $200. Call your local department of health to locate a qualified laboratory. Areas with known elevated levels of radionuclides tend to have a list of qualified laboratories. For a fee some health departments can sample your well. Nobody has the budget to test your well for free.
Once you identify the problem, solving the problem of radionuclides is very direct. The only real concern is drinking water and the possibility of radon carried in the water being released into the home. Reverse osmosis systems installed in the kitchen can be used to remove up to 99% of radionuclides in drinking water with selection of the correct membrane according to the EPA. Removal effectiveness depends on membrane selected, the water pressure and proper installation. Proper selection of the membrane and pressure is essential when selecting a reverse osmosis system. Hard water will cause scaling on the membrane so buy extra membranes and know how to change them. When the water pressure in the sink drops, the membrane is fouled and needs to be changed. The reverse osmosis systems require regular maintenance and monitoring to continue to function properly over an extended period of time.
Though I am not a fan of these systems in many applications, they are the best available technology for radionuclides. Reverse osmosis systems use a lot of water. They recover only 5% to 15% of the water entering the system, so they should only be used for the drinking and food preparation water. Waste water is typically connected to the house drains and will add to the load on the household septic system-it’s like adding an extra person to the septic load. A reverse osmosis system delivering 5 gallons of treated water per day may discharge 40 to 90 gallons of waste water per day to the septic system. This is a significant additional load and could impact the life and functioning of your septic system. You might want to look into other methods to dispose of the waste water.
Effectiveness of reverse osmosis system depends on initial levels of contamination, membrane size and type and water pressure. The application of pressure reverses the natural flow of the flow of water in osmosis from high concentration so that water passes from a more concentrated solution to a more dilute solution through a semi-permeable membrane. Reverse osmosis systems incorporate pre and post-filters along with the membrane itself in order for a reverse osmosis system to function properly. It is common to have a whole house filter system utilizing activated carbon installed in series with the reverse osmosis system. When addressing radionuclides the activated carbon filter can reduce the radon levels carried in the water, solving that problem.
Reverse osmosis units on the market range in cost from $200 to $3000 and vary in quality and effectiveness. Homes on well water need to purchase low pressure units. The size and membrane type are one of the factors that will determine cost. Replacement membranes cost $100 to $200 and filter cartridges around $50 (there are usually several)- it’s like a printer, the money is in selling the supplies. Reverse osmosis is a proven technology that has been used successfully on a commercial basis most famously for removing salt from seawater. Household reverse osmosis systems typically deliver small amounts (2 to 10 gallons per day) of treated water and waste 7 to 20 times the amount of water treated. Reverse osmosis systems can also remove many inorganic contaminants from household drinking water supplies including arsenic, sodium and nitrate. The removal effectiveness depends on the contaminant and its concentration, the membrane selected, the water pressure and proper installation and maintenance.