This is a fact sheet about a chemical that may be found in some public or
private drinking water supplies. It may cause health problems if found
in amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What is Thallium
and how is it used?
Thallium is a metal found in natural deposits as ores containing other
elements. The greatest use of thallium is in specialized electronic
Why is Thallium
In 1974, Congress passed the Safe Drinking Water Act. This law requires
EPA to determine safe levels of chemicals in drinking water which do or
may cause health problems. These non-enforceable levels, based solely on
possible health risks and exposure, are called Maximum Contaminant Level
The MCLG for thallium has been set at 0.5 parts per billion (ppb)
because EPA believes this level of protection would not cause any of the
potential health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a
Maximum Contaminant Level (MCL). MCLs are set as close to the MCLGs as
possible, considering the ability of public water systems to detect and
remove contaminants using suitable treatment technologies.
The MCL has been set at 2 ppb because EPA believes, given present
technology and resources, this is the lowest level to which water
systems can reasonably be required to remove this contaminant should it
occur in drinking water.
These drinking water standards and the regulations for ensuring
these standards are met, are called National Primary Drinking Water
Regulations. All public water supplies must abide by these regulations.
What are the health effects?
Short-term: EPA has found thallium to potentially cause the following
health effects when people are exposed to it at levels above the MCL for
relatively short periods of time: gastrointestinal irritation; nerve
Long-term: Thallium has the potential to cause the following
effects from a lifetime exposure at levels above the MCL: changes in
blood chemistry; damage to liver, kidney, intestinal and testicular
tissues; hair loss.
How much Thallium
is produced and released to the environment?
Thallium is not produced in the US. Approximately 4,500 lbs. of thallium
and its compounds were reportedly imported in 1987. Man-made sources of
thallium pollution are gaseous emission of cement factories, coal
burning power plants, and metal sewers. The leaching of thallium from
ore processing operations is the major source of elevated thallium
concentrations in water. Thallium is a trace metal associated with
copper, gold, zinc, and cadmium.
What happens to Thallium
when it is released to the environment?
Thallium does not long persist if released to water, but does have a
strong tendency to accumulate in aquatic life. If released to land, it
may bind to alkaline soils, but may otherwise migrate to ground water.
How will Thallium
be detected in and removed from my drinking
The regulation for thallium became effective in 1994. Between 1993 and
1995, EPA required your water supplier to collect water samples once and
analyze them to find out if thallium is present above 2 ppb. If it is
present above this level, the system must continue to monitor this
contaminant every 3 months.
If contaminant levels are found to be consistently above the MCL,
your water supplier must take steps to reduce the amount of thallium so
that it is consistently below that level. The following treatment
methods have been approved by EPA for removing thallium: Activated
alumina; Ion Exchange.
How will I know if Thallium
is in my drinking water?
If the levels of thallium exceed the MCL, the system must notify the
public via newspapers, radio, TV and other means. Additional actions,
such as providing alternative drinking water supplies, may be required
to prevent serious risks to public health.
This is a factsheet about a chemical that may be found in some
public or private drinking water supplies. It may cause health problems
if found in amounts greater than the health standard set by the United
States Environmental Protection Agency (EPA).
Drinking Water Standards:
|Mclg: 0.5 ppb (parts per billion)
Mcl: 2 ppb
Releases to Water and Land, 1987 to 1993 (in pounds):
|Top Five States
|Primary copper smelting
|Primary nonferrous metals
|Blast furnaces, steelworks
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water