United States
Environmental Protection
Agency
Office of Pesticides and
Toxic Substances TS-793
Washington D C 20460
xvEPA
Toxics Information
Series
Cadmium—
what is it?
Cadmium
Cadmium,first producedcommerciallyin 1907,is a
valuable industrial metal. Although U.S. production is
relatively low—approximately 1,942 metric tons per
year—large amounts are imported annually for manufac-
turing purposes. Workplace exposure to cadmium has been
regulated for some time because of its known toxic
properties. However, scientists now believe the health
hazards associated with long-term low level exposure in
the environment may be more serious and more widespread
than previously suspected. Cadmium has been included in
the recent carcinogen list of the Carcinogen Assessment
Group of the U.S. Environmental Protection Agency
(EPA). This Information Bulletin describes some of the
known and suspected health hazards of cadmium and what
EPA and others are doing to reduce the risks associated
with cadmium exposure.
A soft, silvery metal, cadmium is a relatively rare
element found in sulfide deposits primarily in zinc
ores, and to a lesser extent in lead and copper ores and
high sulphur coal. Most industrial cadmium is produced
as a by-product of zinc refining.
Cadmium is currently used almost exclusively in the
U.S. in industrial processes (e.g., 1,242 metric tons
were used in the first nine months of 1979). Cadmium is
used for electroplating because it has high retention of
luster, deposits readily and uniformly, has good
solderability characteristics, and is a corrosion
preventive. It is also used in pigments for higher
quality plastics, paints and inks; plastic stabilizers;
as alloys in batteries; and as an alloy in other
processes. As an industrial metal, cadmium is in great
demand because of its many important characteristics:
low electrical resistance, high resistance to corrosion
and heat, colorfastness, lightfastness, long life and
thin coating and precise conformity. Although
substitutes are available for most industrial cadmium
uses, in some cases they tend to be less effective, and
in other instances more toxic than cadmium. One
successful cadmium substitute, recently developed for
use in photocells, is silicon sheet to replace cadmium
sulfide and cadmium telluride in solar energy
production.
-------
Why is Cadmium is hazardous to human health, both in
cadmium a high concentrations for short periods of time and
problem? in low doses for prolonged periods. In the natural
environment, localized cadmium ore deposits would pose
little threat to public health, though there are a few
agricultural areas with very high natural cadmium levels
(e.g., Salinas Valley). Industrial production has
redistributed the metal throughout the environment
causing widespread cadmium contamination.
Approximately 68% of the cadmium in the U<,S0
environment is in waste piles and landfills. Since
cadmium recycling is currently negligible, it is
eventually released as a waste product in some form0
Sewage sludge, used as fertilizer and soil conditioner,
may contain between 1-1500 parts per million cadmium0
Major industrial sources of land destined wastes include
electroplating companies and battery and paint manufac-
turers. Electroplating also accounts for nearly 75
percent of the water-borne cadmium wastes. The largest
single source of cadmium air contamination is zinc
smelters which account for about 50 percent of the air
emissions. However, zinc smelters, which are few in
number and generally located in isolated areas, may pose
a smaller risk to the general public than do other
sources, such as iron and steel mills and municipal
incinerators, which contribute a smaller percentage of
the total emissions, but affect a greater number of
people. Also, cadmium is released into the environment
through its use in pesticides, although this is not a
major exposure route.
As a natural-element, cadmium does not decompose or
break down into less toxic components over time0 Once
released into the environment,, cadmium remains available
for absorption from air, water and soil by various
plants and organisms.
Cadmium is absorbed into the human body by the
inhalation of air-borne cadmium, the smoking of tobacco,
and the ingestion of food and water containing
cadmium. This is scientific consensus that the most
significant route of human exposure is through the food
chain. Air-borne cadmium is mostly a worker exposure
problem. However, fall-out from air-borne cadmium
presents a greater problem when it contaminates
croplands. Likewise, smokers, particularly smokers who
work in industries using cadmium or live near industries
discharging cadmium emissions, run a higher risk of
cadmium-related disease than do other segments of the
population.
Cadmium creates both acute and chronic health
effects. Acute poisoning produces respiratory or
gastrointestinal symptoms. Inhalation of large amounts
of cadmium causes pulmonary enema (fluid retention in
the lungs), with symptoms resembling pneumonia. Severe
edema may result in death. Ingestion of large amounts
of cadmium can cause nausea, vomiting, diarrhea,
abdominal cramping and excessive salivation. Acute
poisoning is very rare; however, chronic exposure to low
levels of cadmium is widespread.
-------
Respiratory disease; Inhalation of cadmium over
prolonged periods of time can cause serious damage to
the respiratory system. Emphysema, commonly thought of
as a smoker's disease, may also be caused by low level
exposure to cadmium fumes and dust over prolonged
periods. Clinical studies indicate .pulmonary capacity
is reduced after exposure to levels as low as 66
micrograms per cubic meter (66ug/m ). from two to twenty-
five years. Laboratory tests using rabbits and rats
have also produced emphysema and other respiratory
ailments in the test animal.
Kidney and liver damages Approximately 70 percent
of the cadmium absorbed by the body" is accumulated in
the kidney and liver. Functional liver damage has been
reported on rare occasions in cadmium workers, but
scientists are more concerned about the effects of
cadmium on the kidneys. Serious structural damage to
the kidneys have been observed in workers exposed to
cadmium over prolonged periods and laboratory tests have
produced like results. Scientists note that prolonged
exposure at 66 ug/m produces proteinuria, usually the
first symptom of kidney disease. The World Health
Organization has recommended that cadmium exposure
should be 57-71 ug/day or less. Major structural damage
has been recorded at levels of 200 ug/m3 in the kidney
kidney. However, some experts believe damage may occur
at half that amount, while others believe that damage
doesn't occur until levels of 300-400 ug/m are reached.
Cancers Recent studies indicate cadmium may also
be a human carcinogen or cancer-causing agent. Like'
other known human carcinogens, cadmium induces mutations
in bacteria and mammalian cells. Laboratory animals
injected with cadmium develop cancer at the site of
injection and in other organs. Reports of significant
increases in prostate cancer in persons occupationally
exposed to cadmium for prolonged periods seem to
corroborate the laboratory data.
Birth defects; Human birth defects attributable to
cadmium have not been documented. Nevertheless, one
study of mothers working in the cadmium industry record-
ed lower birth weights, signs of rickets and delayed
development of teeth in newborn children. Laboratory
tests in which pregnant rats, mice, hamsters and frogs
are fed cadmium have produced birth defects in the
offspring0
Other effectss Cadmium has toxic effects on a
variety of organs and systems in test animals, and there
are indications that humans may be affected in similar
ways. Injection of cadmium into rats, rabbits and dogs
have induced hypertension. Similarly, chronic oral
exposure to low concentrations has created l.yperten-
sion in rats. Direct cause and effect relationship
between cadmium exposure and hypertension, however, has
not yet been established in test animals or humans.
-------
Moderate anemia has been reported in cases of
occupational exposure to cadmium dust and fumes. Anemia
is a common finding in cadmium chronic exposure
experiments with several species of laboratory
animals. Central nervous system disorders have been
observed in storage battery factory workers exposed to
cadmium and brittle bone conditions have been reported
among workers in a variety of cadmium industries0 Also,
people who suffer from iron, calcium, and other dietary
deficiencies are highly susceptible to cadmium
absorption.
What is the Federal regulation of human exposure to cadmium
government cadmium began in the occupational environment where
doing about exposure was the greatest, and has since been expanded
this hazard? to include cadmium contamination of food, land, water
and air. In 1970, the Occupational Safety and Health
Administration (OSHA) adopted occupational exposure
standards set voluntarily by industry in the 1940"s to
curb acute cadmium poisoning. OSHA is currently
reviewing a proposal to lower those limits of Od
milligrams per cubimeter (0=1 mg/m3) for cadmium fumes
and 0.2 mg/m3 for cadmium dusts to 40 migcrograms per
cubic meter (40ug/nr) for combined dust and fumes» (A
milligram is 1/1000 of a gram and a microgram is one
millionth of a gram). The standard is being strenght-
ened to protect workers against the development of
kidney damage which has been reported at exposure levels
as low as 66 ug/nr . '_
The Food and Drug Administration (FDA), concerned
with the dietary intake of cadmium, is surveying foods
available in grocery stores for the presence of cadmium,
and testing the ability of cadmium to leach from
cookware. They are also evaluating current analytical
methods for detecting cadmium in foods. The FDA, EPA
and U.S. Department of Agriculture (USDA) are jointly
involved in a four-year survey (started in 1979) of
6,000 crop samples and 18,000 associated soil samples
from major crop producing regions of the U.S. to assess
cadmium content and availability. A long-term study
sponsored by EPA and USDA is analyzing the flow of
cadmium from sewage sludge in a food chain system
utilizing sludge-fertilized corn fed to dairy goats„
Another EPA and FDA study is examining impacts of
incorporating cadmium-contaminated sewage sludge into
cattle feed.
To curb the increasing cadmium contamination of
soil resources, EPA has established criteria for the
disposal of sewage sludge containing cadmium on
agricultural lands (1979 regulations), and proposes to
promulgate rules for municipal and home use and disposal
of sludge in the near future. Regulations governing the
management of hazardous cadmium wastes from industrial
sources have also been proposed under the authority of
the Resource Conservation and Recovery Act*
-------
To reduce cadmium levels in water, EPA used the
authority of the Clean Water Act in 1979 to set effluent
guidelines which limit the amount of cadmium in waste
water discharges from electroplating plants into
publicly-owned waste water treatment works. A drinking
water standard of 0.01 mg of cadmium per liter of water
has also been set. EPA draft water criteria for cadmium
will serve as the basis for any additional regulation of
cadmium content in water.
The health effects, sources of emissions,
population exposure and risk of cadmium in the air have
been analyzed by EPA and regulation of cadmium as an
airborne carcinogen under the authority of the Clean Air
Act is under consideration. Under the Federal
Insecticide, Fungicide, and Rodenticide Act (FIFRA), EPA
also is conducting an in-depth risk/benefit review of
registered cadmium pesticide uses through the "rebuttal
presumption against registration" (RPAR) process„ This
review could result in continuation, restriction or
final cancellation of the presently registered cadmium
pesticide uses.
In Summary; Cadmium is of concern because of its
known toxicity at very low levels, its bioaccumulation
in soils, its potential as a human carcinogen, and the
widespread exposure of the American public to cadmium
levels which approach those known to cause significant
health hazards. The major uses of cadmium have been
banned by the Swedish Government.
------- |