Transcript Arsenic in Groundwater

Arsenic in Groundwater
Naman Dalal
June 7, 2006
Arsenic Information
• Arsenic is a semi-metal with
an atomic number of 33.
• It is odorless and tasteless,
and is naturally occurring in
rocks and soil.
• Arsenic can be combined with
other elements to make
chemicals that are used to
preserve wood or as insect
killers on cotton crops.
• Organic arsenic which is
mainly found in seafood, is
harmless to the human body.
http://www.epa.gov/safewater/arsenic/index.html
Poisonous Arsenic
• The arsenic that concerns scientists is inorganic arsenic
that pollutes the groundwater. Despite its high toxicity,
inorganic arsenic occurs naturally on earth in small
amounts.
• Inorganic arsenic is a known and documented
carcinogen, leading to skin, lung, liver, bladder, kidney,
and prostate cancer.
• Inorganic arsenic is one of the most toxic substances in
its purest form, and besides cancer as a long term effect,
it can cause infertility, decreased production of red and
white blood cells, and can even damage DNA.
http://www.lenntech.com/arsenic.htm
How are we exposed to it?
• Since arsenic is widely distributed throughout the earth’s
crust, it is introduced into the water through the
dissolution of minerals and ores.
• Industrial waste also contributes to arsenic pollution
when run-off from orchards where arsenic is used
mixes with the groundwater.
• The combustion of fossil fuels also pollutes the
environment with arsenic through atmospheric
deposition when water from rains brings the arsenic to
the ground.
http://www.who.int/mediacentre/factsheets/fs210/en/index.html
Effects of Arsenic poisoning
• Arsenic poisoning is different
from acute poisoning, and
results from a chronic and
long term exposure to arsenic
which produces symptoms
over time.
• The main symptoms of
arsenic exposure include
stomach pain, diarrhea,
vomiting, nausea, numbness
in hands and feet, thickening
and discoloration of the skin,
partial paralysis, and
blindness.
http://www.cdc.gov/ncidod/dpd/healthywater/factsheets/pdf/arsenic.pdf
How Arsenic exposure is
diagnosed
• Arsenic exposure is diagnosed
through tests of blood, urine,
hair and fingernails.
• A urine test will show if you
have been exposed to arsenic in
the last few days.
• A hair or fingernail test shows
arsenic exposure ranging from
the previous six to twelve
months.
• These tests are conducted if
symptoms of arsenic exposure
are present, and they can reveal
if it is truly arsenic that has made
you sick.
http://www.cdc.gov/ncidod/dpd/healthywater/factsheets/pdf/arsenic.pdf
Arsenic in U.S. groundwater
• Most of the high
concentrations of arsenic in
groundwater exist in the West,
Midwest, and Northeast.
• Widespread high
concentrations of arsenic
result mainly from release
from iron oxide that mixes
with the upflow of
geothermal water.
• Due to concentrations
exceeding 50 mg/L, new
standards were set by the
EPA.
http://water.usgs.gov/nawqa/trace/arsenic/
EPA standards of Arsenic in
groundwater
• After having the maximum level of
Arsenic set at 50 ug/L, the EPA
lowered levels to 10 ug/L in 2001.
• Water systems are to comply with
this standard by early 2006 to
ensure the protection of millions
of Americans against chronic
exposure to arsenic in drinking
water.
• These levels are measured by
taking samples from wells across
the country and are tested through
laboratory analysis. They are also
in compliance with the standards
set by the World Health
Organization.
http://www.epa.gov/safewater/arsenic/index.html
Why are these levels set?
• These levels are determined to be the most cost
effective and safest level that can be required in the
nation.
• Money plays an important role in setting the maximum
contaminant levels for any chemical in water, so the
EPA has to mediate between cost and how effective a
standard is.
• After careful revisions of the arsenic rule, it took many
years to change the standard from 50 ug/L to 10 ug/L.
• The ultimate goal of the EPA is for arsenic levels in
water to be 0 ug/L.
http://www.epa.gov/safewater/arsenic/index.html
Arsenic pollution in the
world
• Several nations in the world such as Argentina,
Australia, Bangladesh, Chile, China, Hungary, India,
Mexico, Peru, Thailand, and the U.S. have shown
concentrations higher than the guideline value of 10
ug/L of the WHO.
• Adverse health effects from arsenic exposure have been
documented in China, Bangladesh, India (West Bengal),
and the USA.
• Currently, the worst problem exists in Bangladesh and
West Bengal (India) where millions are being exposed to
unhealthy amounts of arsenic through drinking water.
http://www.who.int/mediacentre/factsheets/fs210/en/index.html
Arsenic in Bangladesh
• Over the past 30 years, drinking
water in West Bengal and
Bangladesh has been improved
to prevent dysentery, diarrhea,
and other adverse effects.
• However, in the 1980’s, scientists
noticed high levels of arsenic as
a side-effect of the current
treatment on water.
• Now, according to some
estimates, arsenic is causing 200,
000 to 270, 000 cancer related
deaths in Bangladesh alone.
http://www.who.int/mediacentre/factsheets/fs210/en/index.html
How Arsenic pollution can
be prevented
• So far, no filtration technique has been proven to be
effective in all types of situations in removing arsenic.
• As scientists continue to lower the concentration of
arsenic in the water that is accepted, the cost and
difficulty to get it that low is increased.
• Although we cannot truly prevent arsenic from being in
our water because it is a naturally occurring element, we
can reduce the amount that is used to preserve wood
and reduce the amount used in alloying agents and other
parts of industry.
http://www.who.int/mediacentre/factsheets/fs210/en/index.html
Why Arsenic pollution is
overlooked in groundwater
• Arsenic enters our water systems
from more than just the rocks
and minerals that contain it, but
now increasingly from industrial
waste.
• Much emphasis about our water
quality was placed on the
amounts of chlorine or nitrates
and phosphates present in our
water.
• Many people still do not realize
that arsenic pollution in water is
creating serious problems across
the world and should not be
ignored any longer.
Further Readings
• World Health Organization http://www.who.int/mediacentre/factsheets/fs210/en/inde
x.html
• USGS - http://www.usgs.gov/nawqa/trace/arsenic/
• US EPA http://www.epa.gov/safewater/arsenic/index.html
• CDC http://www.cdc.gov/ncidod/dpd/healthywater/factsheets/p
df/arsenic.pdf
• LennTech - http://www.lenntech.com/Periodic-chartelements/As-en.htm