United States
Environmental Protection
Agency
Office of Water
4601
EPA811-F-95-002g-T
October 1995
National Primary Drinking
Water Regulations
Selenium
CHEMICAL/ PHYSICAL PROPERTIES
' 3 t'
CAS NUMBER: 7782-49-2
COLOR/ FORM/ODOR: Selenium is a metal which exists in nature
only in the combined form.
SOIL SORPTION COEFFICIENT: N/A
BIOCONCENTRATION FACTOR: BCF of 1000 in humans; 50,000 in
marine fish
SOLUBILITIES:
dioxide-
hydrogen-
sodium-
sulfide-
384 g/L at 14 deg C
3.8 LA at 4 deg C (hydrogen selenide)
850 g/L at 20 deg C
insoluble
COMMON ORES: Usually found in the sulfide ores of the heavy
metals, such as pyrite, clausthalite, naumannite, tiemannite.
Also found in coal.
DRINKING WATER STANDARDS
MCLG: 0.05 mg/l
MCL: 0.05 mg/l
HAL(child): none
HEALTH EFFECTS SUMMARY
Acute: Selenium is an essential nutrient at low levels.
However, EPA has found it to potentially cause the
following health effects from acute exposures at levels
above the MCL: hair and fingernail changes; damage to
the peripheral nervous system; fatigue and irritability.
No Health Advisories have been established for short-
term exposures.
Chronic: Selenium has the potential to cause the
following health effects from long-term exposures at
levels above the MCL: hair and fingernail loss; damage
to kidney and liver tissue, and the nervous and circula-
tory systems.
Cancer: There is no evidence that selenium has the
potential to cause cancer from lifetime exposures in
drinking water. •-.:."
*
USAGE PATTERNS
Selenium is used extensively in the manufacture and
production of glass, pigments, rubber, metal alloys,
textiles, petroleum, medical therapeutic agents, and
[photographic emulsions. Selenium dioxide is the most
widely used selenium compound in industry. It is used as
an oxidizing agent in drug and other chemical manufac-
ture; a catalyst in organic syntheses; an antioxidant in
lubricating oils.
Production in 1985 was reported to be429,515 pounds,
with demand for its various uses as follows: electronic
and photocopier components, 35%; Glass manufactur-
ing, 30%; Chemical and pigments, 25%; and Other, 10%.
RELEASE PATTERNS
There are no true deposits of selenium anywhere and
it cannot economically be recovered from the earth
directly. It usually occurs in the sulfide ores of the heavy
metals; this includes pyrite, clausthalite, naumannite,
tienammite and in selenosulfur. Soils in the neighbor-
hood of volcanoes tend to have enriched amounts of
Toxrc RELEASE INVENTORY -
RELEASES TO WATER AND LAND: 1987 TO 1993
TOTALS (in pounds)
Top Five States *.
UT
AZ
Wl
IN
TX
Water
1 3,556
1,578
0
0
5,300
359
Major Industries*
Copper smelting, refining 1 ,500
Metal coatings 0
Petroleum refining 8,949
. Land
1,010,686
696,515
260,632
45,000
0
4,920
962,067
45,000
977
* Land totals only include facilities with releases greater than
1000lbs.
October 1995
Technical Version
Printed on Recycled Paper
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selenium. Selenium is the most strongly enriched ele-
ment in coal, being present as an organoselenium com-
pound, a chelated species, or as an adsorbed element.
Selenium compounds are released to the air during the
combustion of coal and petroleum fuels, and during the
smelting and refining of other metals.
From 1987to 1993, according to the Toxics Release
Inventory selenium releases to land and water totalled
over 1 million IDS., of which about 99 percent was to land.
These releases were primarily from copper smelting
industries. The largest releases occurred in Utah. The
largest direct releases to water occurred in Indiana.
Selenium concentration in fresh water is usually around
0.02 ppm. The selenium content of surface water is
greatly influenced by pH, being high in acidic (pH < 3.0)
and in alkaline waters (pH > 7.5). Traces of selenium
ranging from 0.0000-0.01 ;ppm are commonly found in
community drinking water.
ENVIRONMENTAL FATE
The toxicity of selenium depends on whether it is in the
biologically active oxidized form. In alkaline soils and
oxidizing conditions, selenium may be oxidized suffi-
ciently to maintain the availability of its biologically active
form, and cause plant uptake of the metal to be in-
creased.
In acidic or neutral soils, it tends to remain relatively
insoluble and the amount of biologically available sele-
nium should steadily decrease. Selenium volatilizes from
soils when converted to volatile selenium compounds
(such as dimethyl selenide, dimethyl diselenide, and
others) by microorganisms.
It is known that selenium accumulates in living tissues.
For example, the selenium content of human blood is
about 0.2 ppm. This value is about 1000 times greater
than the selenium found in surface waters. It is clear that
the human body does accumulate or concentrate sele-
nium with respect to the environmental levels of sele-
nium. Selenium has been found in marine fish meal at
levels of about 2 ppm. This amount is around 50,000
times greater than the selenium found in seawater.
Selenium dioxide is the primary source of problems
from industrial exposures since the dioxide forms sele-
nious acid with water or sweat, and the acid is an irritant.
Selenium compounds released during coal or petroleum
combustion may be a significant source of exposure.
OTHER REGULATORY INFORMATION
MONITORING:
• FOR GROUND WATER SOURCES:
INITIAL FREQUENCY- I sample once every 3 years :
REPEAT FREQUENCY- If no detections tor 3 rounds, once every 9 years
- FOR SURFACE WATER SOURCES:
INITIAL FREQUENCY- ' 1 sample annually
REPEAT FREQUENCY- If no detections for 3 rounds, once every 9 years
- TRIGGERS - If detect at > 0.05 mg/L, sample quarterly.
METHODNUMBERS
270.2
D3859-84A; 03859-88
3113B;3114B
ANALYSIS:
REFERENCE SOURCE
EPA 600/4-79-020
ASTM Standards 1991
Standard Methods (17th ed.)
TREATMENT
BEST AVAILABLE TECHNOLOGIES
Activated Alumina, Coagulation/Filtration (SeVI only). Lime Softening, Re-
verse Osmosis, Electrodialysis
FOR ADDITIONAL INFORMATION:
* EPA can provide further regulatory and other general information:
• EPA Safe Drinking Water Hotline - 800/426-4791
4 Other sources of lexicological and environmental fate data include:
• Toxic Substance Control Act Information Line - 202/554-1404
• Toxics Release Inventory, National Library of Medicine - 301/495-6531
• Agency for Toxic Substances and Disease Registry - 404/639-6000
October 1995
Technical Version
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