What is Radium?
Radium is a naturally-occurring, silvery-white, radioactive material
that can exist in several forms called isotopes. Radium is formed
when uranium and thorium (two other natural radioactive substances)
decay (break down) in the environment. Radium is almost everywhere:
in soil, water, rocks, plants, and foods at low levels.
Radium only degrades by radioactive decay. Each isotope of radium
releases radiation at its own rate. The concentrations of radium-226
and radium-228 in drinking water are generally low, but there
are some areas where high concentrations of radium occur due to
geologic sources.
In the U.S., radioactivity is usually measured in units called
"curies". The level of radioactivity in water is usually
very low and is measured in picocuries (one picocurie equals one-trillionth
of a curie) per liter (pCi/l).
Is Radium in My Water?
Surface water is usually low in radium but groundwater can contain
significant amounts of radium due to local geology. Drinking water
from wells can contain radium-226 and radium-228 at levels above
regulatory standards. High radium levels can be due to the presence
of radium in the rock or sands from which the well water is drawn.
What Levels of Radium are Safe?
The EPA's maximum contaminant level (MCL) for radium (Radium-226
and Radium-228 combined) in public water supplies is 5 picocuries
per liter (pCi/l). The MCL has been set well below levels for
which health effects have been observed. It is therefore assumed
to be protective of public health. EPA estimates the additional
lifetime risks associated with drinking water containing 5 pCi/l
is about 1 in 10,000. Public water supplies whose radium levels
exceed 5 pCi/l are not inherently "unsafe" but are required
to notify the public that the water exceeded the MCL. Water containing
elevated levels of radium may carry a correspondingly higher level
of risk to health. |
