What is a drinking water PAG?

The drinking water Protective Action Guide is a health-based value that can be used in the event of a nationally significant radiological emergency to determine when alternative drinking water should be provided and the use of contaminated water supplies be restricted. The drinking water PAG are doses of radiation that should be avoided during an emergency event. They do not represent acceptable routine exposures. PAGs apply to emergency situations only. They trigger safety measures—in this case, provision of alternative drinking water—to keep doses to the public as low as possible.

How does the drinking water PAG work with EPA’s existing Safe Drinking Water Act regulations?

The drinking water PAG is non-regulatory guidance for emergency situations only. Immediately following a radiological incident, community water systems must return to compliance with EPA’s Radionuclides Rule^[1]. Public water suppliers will be required to take corrective measures to meet radionuclide standards as soon as practicable.

Why is there a need for a drinking water PAG when EPA already has regulations for radionuclides in drinking water?

Under the Safe Drinking Water Act (SDWA), the Agency established a dose-based Maximum Contaminant Level (MCL) for beta particle and photon (gamma) radioactivity of 4 millirem per year (mrem/yr); based on lifetime exposure criteria, which assume 70 years of continued exposure to contaminants in drinking water.

The Agency determined that it may not be possible to base response measures during short-term emergency incidents on lifetime exposure criteria. While the SDWA framework is appropriate for day-to-day normal operations, it does not provide the necessary tools to assist emergency responders with determining the need for prioritizing protective actions during the intermediate phase of a response.

Regardless of the cause of an incident, EPA expects that any drinking water system impacted during a radiation incident will take action as soon as practicable to return to compliance with the SDWA levels as soon as practical

How will my children and I be protected during a radiological emergency?

• Emergency responders, state and local authorities have emergency plans in place to protect public health by helping individuals avoid doses of radiation.
• State or local government officials will take reasonable precautionary measures to protect water supplies as soon as they are aware of the radiological incident.
• Public water suppliers are expected to be in close communication with their state/local officials.
• The drinking water PAG can be used to inform decisions about continued use of contaminated water for drinking purposes and to inform decisions to provide alternative drinking water for the affected community.

At what point and what concentrations will I be told to stop drinking tap water during a radiological emergency?

State and local officials make decisions about continued use of tap water based upon the conditions on site during a radiological emergency.  The drinking water PAG provides information they can consider including two scientifically-based levels to be avoided (100 mrem for infants, children aged 15 and under, pregnant women and nursing women; 500 mrem for anyone over age 15 excluding pregnant women and nursing women) for periods up to one year. Since this is only guidance, the levels selected by your state or local officials will depend on the type and severity of the incident.  You may not be instructed to stop drinking tap water. Your water department—in coordination with state/local officials and emergency managers—may choose to either use water from storage tanks that have not been impacted by radiation, purchase water from a neighboring town, transport water in tanker trucks or provide bottled water to the community.

^[1] For more information about EPA’s regulations for radionuclides in drinking water, refer to the Radionuclides Rule:  A Quick Reference Guide: