Is
Manganese in Drinking Water a Neurotoxin?.
In the March 3rd 2014 Time
Magazine, Alice Park reminds us that low level exposure to many substances can
impact development in children.
One of the substances cited, almost as a
throwaway is manganese in drinking water.
Manganese concentration in
drinking water is not regulated in the United States, but the U. S.
Environmental Protection Agency (EPA) has a health-based “guideline” of is 300
µg/L maximum level.
However, EPA recommends a
"secondary maximum contaminant levels" for manganese for aesthetic
considerations, such as taste, color and odor of 50 µg/L of manganese in
drinking water. The World Health Organization recommends a limit of 400 µg/L of
manganese.
There have been very few
studies of the possible neurotoxic impacts from chronic low level exposures,
the kind of exposure to manganese that would occur from drinking water supplied
from groundwater.
The largest study
(involving 362 children from 251 families) was performed in Canada using
communities with a public water supply and private water supplies from
groundwater with a natural manganese levels from the bedrock geology and not
human activities.
The tap water concentration
of manganese ranged from 1 to 2,700 µg/L manganese. (MMT the gasoline additive
containing manganese has been banned in Canada since 2004, but the highest
concentrations of manganese found in that study seem very high.
In New England, 45% of
wells for public use have manganese concentrations greater than 30 µg/L.
According to a 2009 report by the U.S. Geological Survey, about 5% of domestic
household wells in the United States have manganese concentrations greater than
300 µg/L.)
The study, “Intellectual
Impairment in School-Age Children Exposed to Manganese from Drinking Water,” was published in 2010 in
Environmental Health Perspectives, the Canadian journal and is fully cited
below examined possible neurotoxic effects from manganese at concentrations
they claim are commonly found in North American aquifers.
The scientists assessed the
relationship between exposure to manganese from drinking water and IQ of
school-age children living in communities relying on groundwater.
In addition, they examined
the relations between manganese concentration in hair follicles and estimated
manganese intakes from water consumption and from the food.
Until recently, exposure to
manganese from water consumption has been of little concern, because the intake
of manganese from ingestion of water is small compared with that from foods,
except in the case of infants.
In the Canadian study they
discovered though manganese consumption from water was very small compared with
the
amount ingested
from foods (by more than two orders of magnitude), yet only consumption from
water was significantly associated with manganese concentration in the hair
follicles of the children.
.
The mechanism
of manganese uptake into hair is not well understood, but it has long been postulated that
its affinity for melanin, a protein present in hair, skin, and the central
nervous system, could be involved. Though the children had all lived at the
same locations for at least 12 months, the duration of that level of exposure
is not known.
The scientists found that
IQ scores decreased steadily with increasing manganese concentrations in the
drinking water. Children in the highest manganese concentration quintile
(median, 216 µg/L) scored 6.2 IQ points below those in the lowest quintile
(median, 1 µg/L).
It is not known whether
exposure during a critical developmental period is responsible for their
observations. Interestingly enough, manganese concentrations in drinking water
were lower in houses with private wells than houses served from the public well
(8 µg/L versus 55 µg/L ).
.
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RELATED POSTS:
Iron
& Manganese in Groundwater
Colors and Smells
http://puricare.blogspot.com/2016/09/color-appearance-taste-smell-and-odor.html
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Elizabeth Ward was awarded an MBA from the University of Pittsburgh and an MS ChE from Polytechnic Institute of NYU, worked as a chemical engineer for both the US EPA in DC, and at DuPont before working in finance and then becoming consultant with Washington Advisors and is the author of "The Lenders Guide to Developing an Environmental Risk Management Program." Elizabeth retired from Washington Advisors and began her volunteer career and is currently the Treasurer of the Prince William Soil and Water Conservation District.
http://greenrisks.blogspot.com/search/label/manganese
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