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RADIONUCLIDES AND THEIR MCUS
<br />By Randy Thielemier
<br />CRWA, Circuit Rider 2
<br />Some radionuclides occur naturally as
<br />trace elements in rocks and soils, others are
<br />man -made. EPA has set limits (or maximum
<br />contaminant levels (MCL)) in drinking water
<br />for four groupings of radionuclides:
<br />1. 2 kinds (or isotopes) of radium —ra-
<br />dium -226 and radium -228
<br />2. Gross alpha emitters
<br />3. 3 uranium isotopes— uranium -234, uranium -235, and ura-
<br />nium -238
<br />4. 179 man -made beta and photon emitters
<br />The nucleus of a radioactive element is unstable. This means
<br />the element is transformed into other elements by emitting
<br />particles and /or high energy from the nucleus or other parts of
<br />the atom. This process is called "radioactive decay." The regu-
<br />lated naturally occurring radionuclides are gross alpha particles,
<br />radium -226, radium -228 and uranium isotopes 234,235,and 238.
<br />These are all the result of the radioactive decay of uranium -238
<br />(U -238) or thorium -232 (Th -232).
<br />The energy released by radioactive decay is called "ionizing
<br />radiation" in the form of alpha, beta, or gamma radiation. Each
<br />type of radiation is energetic enough to break chemical bonds
<br />that are able to damage or destroy living cells. Ionizing radiation
<br />pulls electrons off atoms in the cells and may prevent the cell
<br />from functioning properly. It may lead to the cell's death, to the
<br />cell's inability to repair itself, or to the cell's uncontrolled growth
<br />(cancer). Ionizing radiation is a known human carcinogen.
<br />Alpha emitters naturally occur as radioactive contaminants,
<br />but several come from man made sources. They may occur in
<br />either groundwater or surface water. At high exposure levels,
<br />alpha emitters may cause cancer in some humans.
<br />Beta and photon emitters are primarily man -made radioactive
<br />contaminants associated with operating nuclear power plants,
<br />facilities that use radioactive material for research or manufac-
<br />turing, or facilities that dispose of radioactive material. Beta and
<br />photon emitters primarily occur in surface water. Some beta
<br />emitters occur naturally such as potassium -40 and elements of
<br />the U -238 orTh -232 decay series. Naturally occuring beta emit-
<br />ters occur in ground water and surface water. At high exposure
<br />levels, beta and photon emitters may cause cancer in some hu-
<br />mans. The CDPHE will determine if your system is'vulnerable',
<br />and if you have to monitor for these contaminants.
<br />Radium -226 and radium -228 are natural groundwater con-
<br />taminants that usually occur at trace levels. At high exposure
<br />levels, radium -226 and radium -228 can cause bone cancer in hu-
<br />mans and may cause stomach, lung, and other cancers as well.
<br />Radon is a naturally occurring radioactive gas that emits ion-
<br />izing radiation. National and international scientific organiza-
<br />tions have concluded that inhaling radon gas may cause lung
<br />cancer in humans. Ingesting drinking water that contains radon
<br />gas may also present a risk of internal organ cancers, primarily
<br />stomach cancer. If you smoke and your home has high indoor
<br />radon levels,your risk of lung cancer is especially high. Tap water
<br />emits approximately 1 to 2 percent of the radon found in indoor
<br />air. However, breathing radon from this source may increase the
<br />risk of lung cancer over the course of a lifetime. There is no MCL
<br />for radon in drinking water at the State or national level.
<br />Uranium is a naturally occurring radioactive contaminant
<br />that is found in both groundwater and surface water. Uranium
<br />is toxic to the kidneys and may cause bone cancer and other
<br />cancers in humans.
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<br />COLORADO DEPARTMENT OF PUBLIC HEALTH AND
<br />ENVIRONMENT MAXIMUM CONTAMINANT LEVELS (MCL)
<br />AND COMPLIANCE
<br />Maximum Contaminant Level (MCL): Radionuclide MCLs ap-
<br />ply to all community public water systems in Colorado:
<br />1. Combined radium -226 and radium -228 5 pCi /Liter
<br />(This is the analytic result for radium -226 added to the ana-
<br />lytic result for radium -228)
<br />2. Gross alpha particle activity 15 pCi /Liter
<br />(Includes radium -226 but excludes uranium)
<br />3. Beta particle and photon radioactivity 4 mrem /Year
<br />(Average annual concentration from man made radionu-
<br />clides in drinking water must not produce an annual dose
<br />to the body or any internal organ greater than this value)
<br />4. Uranium 30 Ng /Liter
<br />Monitoring: All community systems must conduct initial
<br />monitoring, at each entry point to your distribution system to
<br />determine compliance with #1,#2, and #4 above by December 31,
<br />2007. CDPHE includes these monitoring requirements with your
<br />sampling schedule for the year that you are required to monitor.
<br />CDPHE may at its discretion, use the results from the period
<br />between June 2000 and December 8,2003, to satisfy initial moni-
<br />toring requirements (often referred to as grandfathering data).
<br />Community systems without appropriate historical data will be
<br />required to collect four (4) consecutive quarterly samples at each
<br />entry point to the distribution system before December 31, 2007.
<br />To reduce the costs of quarterly monitoring requirements
<br />compositing of samples is allowed. For radionuclide sampling,
<br />the samples to be composited are taken from a single entry point
<br />to the distribution system over a period of two (2) consecutive
<br />quarters. The analysis must be done within the six (6) month
<br />holding time forthe first sample collected. The compositing must
<br />be done by the laboratory. The recommended way to sample is
<br />to take individual quarterly samples and send those samples to
<br />the lab each quarter for analysis. In addition, if the first two (2)
<br />quarterly samples are below the regulatory cited detection limit,
<br />CDPHE may waive the final two (2) quarters of monitoring.
<br />If after the initial monitoring, the running annual average is
<br />above the MCL at any sample point, the system is in violation.
<br />The system must take quarterly samples at that sample point
<br />until it has four (4) consecutive quarters that are below the MCL
<br />or until the monitoring frequency is changed as a result of an
<br />enforcement order.
<br />MCL violations are generally a Tier 2 violation, and requires
<br />public notification within 30 days of the system being notified of
<br />the violation according to the Colorado Primary Drinking Water
<br />Regulations, Section 9.2.3. The system must also includethe viola-
<br />tion on the next annual consumer confidence report as required by
<br />Section 9.1 of the Colorado Primary Drinking Water Regulations.
<br />If the initial monitoring results are below the MCL at a sample
<br />point, CDPHE will determine your next sampling frequency at
<br />each sampling point in accordance with the Colorado Primary
<br />Drinking Water Regulations, Section 6.3.2 (c). If the gross alpha
<br />activity measurement is 5 pCi /L or less, you can substitute this
<br />result for the required radium -226 measurement. If the gross
<br />alpha activity measurement is 15 pCi /L or less,you can substitute
<br />this result for the required uranium measurement. See Colorado
<br />Primary Drinking Water Regulations, Section 6.3.2 (e) and 6.3.2
<br />(c) for monitoring frequency impact.
<br />( Reference; Colorado Primary Drinking Water Regulations, amended
<br />Jan.26,2004:Table 2 -7, Section 6.3,Section 9.2.3; National Drinking Water
<br />Clearinghouse; Tech brief: Radionuclides)
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