14 July 2003
Cadmium Found to Mimic Estrogen
Randolph E Schmid
heavy metal cadmium, widely used in batteries and alloys, can affect
rats in ways that mimic the female hormone estrogen, a new study
say the study suggests the metal may be a risk factor for breast
cancer. Scheduled for the August issue of the journal Nature Medicine,
the study is being published online Monday.
never expected to see this strong a relationship, given how different
the cadmium and estrogen compounds are," said Mary Beth Martin
of Georgetown University. "Cadmium's ability to functionally
mimic estrogen and its effect on cell growth is quite remarkable."
we saw suggests a direct link between low dose cadmium exposure
and increased risk of breast cancer," she said.
has long raised environmental concerns because chronic exposure
can lead to kidney damage and bone disease.
the study found that even relatively low doses of cadmium affected
the mammary glands and sexual development of the animals.
effects included an increase in weight of the uterus, changes in
the lining of the uterus and increased density of the mammary glands.
In rats exposed to cadmium while still in the womb, there were changes
in their mammary glands and puberty began earlier than normal, reported
studies in male rats showed changes in the prostate after administration
of cadmium, Martin said.
said it's too early to predict that the metal would affect human
in the same way it does rats, but the findings suggest that it may
be a hazard.
onset of puberty can increase a woman's risk of breast cancer, and
increased breast density can also be an indication of the disease.
more we learn about how this works in rats, and eventually people,
the better lifestyle choices women can make," she said.
tests were designed to see the effect of cadmium at levels that
might be encountered in real life.
World Health Organization recommends a maximum exposure of 7 micrograms
of cadmium per kilogram of weight per week. The rats were injected
with the equivalent of 5 micrograms per kilogram of weight.
the United States, dietary exposure to cadmium is estimated to range
from 0.12 microgram to 0.49 microgram per kilogram daily.
metal is common in pigments, alloys and batteries and can be encountered
in soldering processes. It is also an air contaminant produced by
burning fossil fuels and is present in foods, particularly shellfish,
liver and kidney. Cigarette smoking can add 2 to 4 micrograms of
cadmium per pack.
their experiments, the researchers first removed the ovaries of
female rats, eliminating the animals' main source of estrogen, Martin
the animals recovered from the surgery, some were injected with
cadmium while others were given estradiol, a common form of estrogen.
days later, there was a 3.8-fold increase in the uterus weight in
rats given estradiol to replace their normal estrogen.
the rats given cadmium also had a growth in uterine weight, which
increased 1.9-fold, an indication that they were reacting to the
metal as though it were a hormone.
addition, some of the rats given cadmium were also given a chemical
known to block the effects of estrogen. Those did not have an increase
in uterus weight, Martin reported.
treated with both estradiol and cadmium showed 50 percent increases
in the density of the tissue in the mammary glands, the study found.
said the relatively low dose of cadmium needed to produce the results
was a surprise.
researchers found no toxic effects on the animals' livers or kidneys.
of cadmium into pregnant rats did not change the pregnancy, but
the female offspring reached puberty earlier than rats not exposed
to the metal and their mammary glands developed more fully.
© 2003 The Associated Press