Does manganese inhaled from the shower represent a public health threat
WINSTON-SALEM, N.C. ? A new analysis based on animal studies suggests that
showering in manganese-contaminated water for a decade or more could have
permanent effects on the nervous system. The damage may occur even at
levels of manganese considered safe by the Environmental Protection Agency,
according to researchers from Wake Forest University School of Medicine.
"If our results are confirmed, they could have profound implications for
the nation and the world," said John Spangler, M.D., an associate professor
of family medicine. "Nearly 9 million people in the United States are
exposed to manganese levels that our study shows may cause toxic effects."
The study is the first to show the potential for permanent brain damage
from breathing vaporized manganese during a shower. It was conducted by
reviewing the medical literature and calculating, based on animal studies,
the amount of manganese people would absorb by showering 10 minutes a day.
Because manganese is monitored in public water supplies, high levels of
this naturally occurring metal are especially found in wells and private
water supplies.
Spangler and Robert Elsner, Ph.D., published their findings in the current
issue of Medical Hypotheses, a forum for ideas in medicine and related
biomedical sciences.
The journal publishes "interesting and important theoretical papers that
foster the diversity and debate upon which the scientific process thrives."
Everyone is exposed to small levels of manganese, which is found in food
and many types of rocks and enters the air, soil and water. But, at higher
levels, manganese is toxic to the central nervous system and can cause
learning and coordination disabilities, behavioral changes and a condition
that is similar to Parkinson's disease.
Children, pregnant women, the elderly, and patients with liver disease are
at highest risk from manganese toxicity. Some of these groups have
developed manganese poisoning even at fairly low doses in their water
supplies, Spangler said.
The Environmental Protection Agency (EPA) has set 0.5 milligrams/liter as
the upper limit of manganese advisable in water supplies. The limit,
however, is based on odor and taste of the water. The potential risk of
manganese accumulating in the brain through showering has not been
considered by the EPA in setting this limit. In their analysis, Spangler
and Elsner found that concentrations well below 0.5 milligrams might lead
to brain injury.
"Inhaling manganese, rather than eating or drinking it, is far more
efficient at delivering manganese to the brain," said Spangler. "The nerve
cells involved in smell are a direct pathway for toxins to enter the brain.
Once inside these small nerves, manganese can travel throughout the brain."
Elsner and Spangler extrapolated data from rodents to estimate human
exposure to manganese during showering. They found that after 10 years of
showering in manganese contaminated water, children would be exposed to
doses of manganese three times higher than doses that resulted in manganese
deposits in the brains of rats. Adults would be exposed to doses 50 percent
higher than the rodents.
The researchers said that while limitations to their calculations do exist,
regulatory agencies have not considered this potential pathway when setting
drinking water standards.
"Studies should be carried out among populations that have experienced high
levels of manganese in their water supplies over long periods of time,"
Spangler said. "Regulatory agencies may one day need to rethink existing
drinking water standards for manganese."
The addition of manganese to gasoline as an anti-knock agent may also be a
threat, the researchers said.
"The manganese, as it settles from car exhaust onto streets and highways,
may enter the water supply, increasing manganese levels in the water we
drink and bathe in," said Spangler.
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Media Contacts: Shannon Koontz, shkoontz@xxxxxxxxxx; Karen Richardson,
krchrdsn@xxxxxxxxxx; at 336-716-4587
About Wake Forest University Baptist Medical Center: Wake Forest Baptist is
an academic health system comprised of North Carolina Baptist Hospital and
Wake Forest University Health Sciences, which operates the university's
School of Medicine. The system comprises 1,187 acute care, psychiatric,
rehabilitation and long-term care beds and is consistently ranked as one of
"America's Best Hospitals" by U.S. News & World Report.
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