Monitoring Radionuclides in Drinking Water and Food: Routinely and After a Release
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Various US federal and state agencies are responsible for routine monitoring of drinking water and certain foods, including milk, for the presence of various contaminants including radionuclides.
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Which agency has jurisdiction depends on whether food, water, or milk is being monitored for contamination.
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Enhanced monitoring may be done if radiation or other kinds of hazardous incidents occur.
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Agencies also establish policies for intervening if certain levels are identified.
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Federal and state entities (and other countries) may have different monitoring and intervention policies.
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What is measured?
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Level of radiation in food or water, in Bq/kg or Bq/liter; or pCi/kg or pCi/liter
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How is the measured level of contamination used?
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The goal is to detect levels of radioactive contaminants, which, if ingested, could lead to individuals or populations receiving a predetermined radiation dose (in units of rem or mSv) which should be avoided.
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That predetermined dose to be avoided is known as the Protective Action Guideline (PAG).
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Various national and international organizations have studied risks from radiation, and their data have been used to establish PAGs.
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Protective Action Guidelines (PAGs)
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PAGs (specific dose levels) and contamination limits and are used together as guides which help officials in emergency conditions recommend Protective Actions that will avoid or minimize accumulation of a projected radiation dose either
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Over a lifetime of chronic intake or
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From a single acute exposure
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May refer to a projected dose absorbed by
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The whole body or
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A specific organ, like the thyroid
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May vary by age group, and are usually lower for children and infants
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Selected guidance documents
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Protective Actions
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Are formal prevention or mitigation strategies recommended by officials to reduce or avoid the chance of individuals or populations reaching a PAG (dose level).
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May include
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Interdiction of foods, milk, and water
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Shelter-in-place
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Evacuation
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Medical countermeasures, like potassium iodide
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Note especially that
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Different units are used to express
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Levels of contaminants (in units of Bq/kg or Bq/liter; pCi/kg or pCi/liter)
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Doses to people used in PAGs (in units of rem or mSv)
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Various agencies and countries may have different
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Allowable levels of contamination for specific isotopes in water, or milk, or food
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Protective Action Guidelines (PAGs)
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Methods of implementing Protective Actions
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Derived Intervention Levels (DILs): set by the Food and Drug Administration (FDA)
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When FDA tests food for radioactive contamination, it measures how much radiation is released by radioactive materials that are not expected to be naturally present.
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Unit of measure is typically Bq/kg.
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FDA uses DILS, a calculated value, to enhance food safety.
- It is not an arbitrary level that distinguishes between safe and unsafe food.
- It is one way to estimate the potential for increased risk (of cancer) if enough of a contaminated food is eaten over time to reach the established PAG.
- Even if someone were to consume a food contaminated to the level of a DIL for a whole year, they would not likely receive the PAG dose because of the conservatism built into the calculation of the DIL.
- DIL is one factor FDA uses to help decide whether intervention may be recommended.
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Published DILs are specific for each radionuclide.
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The criteria used to set DILs include the
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Percentage of potentially contaminated foods in a persons diet
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Amount of food typically eaten
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Length of time that a person may be expected to eat contaminated food
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Potential exposure to contaminated foods of different members of the population, including infants and children.
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In general, DILs apply to all foods.
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FDA does not have different DILs for different types of food, though DILs may be adjusted based on, for example, whether a food must be rehydrated before being ready to eat.
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Selected FDA guidance documents about radiation and food safety
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Maximum Contamination Levels (MCLs): set by the Environmental Protection Agency (EPA)
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Is the "maximum permissible" level of a specific contaminant, including specific radionuclides, in water delivered to any user of a public system
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Basic information about radionuclides in drinking water (Safe Drinking Water Act, EPA)
- EPA has proposed that the Safe Drinking Water Act standard should control drinking water recommendations during a radiological emergency.
- Some state and federal agencies have proposed less restrictive alternatives to the MCL approach.
- Reconciliation between the radiation MCL and an emergency drinking water PAG may be necessary during an incident as the potential cost of alternative sources needs to be weighed against the very low risk tolerance associated with the MCLs.
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Under the Safe Water Drinking Act, the Environmental Protection Agency (EPA) has jurisdiction in this area.
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Selected guidance documents
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Monitoring of milk
- Various agencies monitor and regulate radiation in milk.
- EPA conducts routine radiological monitoring of milk under its RADNET program.
- In emergencies, enhanced and targeted monitoring of specific concerns is likely, and levels of concern would be reported to agencies with regulatory responsibility.
- The FDA also does routine, periodic sampling of some but not all U.S. milk products through its "Market Basket Survey".
- FDA has regulatory jurisdiction over the safety, labeling and identity of milk and milk products in interstate commerce. In emergencies, enhanced and targeted monitoring of specific concerns is likely.
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States have jurisdiction over those facilities located within their territory.
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