ABSTRACT

1
ABSTRACT The 20th most abundant element found
in the Earth is Arsenic (As). This element
naturally occurs as As (III) and As (V). These
two oxidation states determine toxicity levels
and control its fate and transport into the human
body, via geologic processes. Sources of arsenic
exposure include contaminated ground water, coal,
geothermal springs, volcanic sediments, and
anthropogenically-related releases. Arsenite
(H3AsO3) is the dominant species of As (III) in
solution and is strongly absorbed onto iron
oxides and other soil constituents (e.g. clay).
Arsenate (H3AsO4) is the most common form of As
(V) and highest absorption rates occur when pH
falls between 4 and 7. As is highly mobile in the
hydrosphere and poses a widespread public health
concern. Exposure to Arsenic can come from both
natural and anthropogenic activities. The most
common toxic pathway is via groundwater, where
the most acute cases are associated with Asian
countries. West Bengal and Bangladesh, in
particular, suffer from rampant arsenic
poisoning, often interpreted as the result of
agricultural irrigation. In heaviest impacted
areas, concentration levels range up to 500 ppb
(parts per billion), whereas background levels
usually average between 3 and 20 ppb. Chinas
Guizhou Province suffers from As poisoning via
lithologic pathways, thought to be intensified by
use of domestic coal fuel associated with
concentrations up to 3500 ppb. Long term exposure
to As, whether air born, in food supplies, or
drinking water, may result in cardiovascular
disease, neurological disorders, skin
depigmentation, rhagades, hyperkeratosis and
Bowens Disease (squamous cell carcinoma). This
paper examines the global impact of environmental
arsenic and its range of human health effects.
Figure 6. Environmental Health Perspectives
Volume 108, Number 5, May 2000
Figure 8. Geologic, Hydrologic, and
Geochemical Characterization of the Deep Ground
Water Aquifer System In the Bengal Delta of
Bangladesh, 2010
Figure 9. Arsenic-induced hyperkeratosis causing
skin ulceration, which leads to
skin cancer
Figure 7. 10-year old girl suffering from
arsenic poisoning, hyperkeratosis
Figure 3. Block Diagram showing principal
geochemical processes involved in the generation
of high-arsenic groundwater in Bangladesh
CHINAS GUIZHOU PROVINCE China does not
experience high levels of arsenic in drinking
water however they do use geogenic coal from the
area. Coal in this area contains extraordinarily
high concentrations of arsenic because it is
bound to the organic components and can contain
up to 35,000µ per gram of coal. (Centeno et al,
2007) Chili peppers dried over coal burning
stoves are believed to be the main source of
poisoning. The dried peppers have been found to
have up to 500µ per gram while chili peppers
freshly picked contained as little as 1 µ per
gram. (Centeno et al, 2007) Chili peppers are a
main ingredient in the Chinese diet so the
population in this area is at risk of poisoning.
Other ways arsenic infiltrates the human body is
by inhalation of combusted coal and dust from the
local area. The population infected is in the
thousands, a much smaller case than Bangladesh,
but a relevant one. Those who are infected show
typical symptoms of As poisoning such as Bowens
Disease and hyperkeratosis. (Centeno et al, 2007)
See Figures 9, 10, 11
INTRODUCTION Arsenic is a naturally occurring
element that can be found within the lithosphere.
There is scientific research that has been
documented depicting areas in which especially
high concentrations of As have been found. Due to
natural geologic processes, concentrated arsenic
is able to infiltrate the hydrological cycle and
enter the human body. Another way human health is
impacted via geologic processes is by use of coal
containing high concentrations of As. Health
impacts from Arsenic vary immensely, such as
squamous cell carcinoma and cardiovascular
disease. The variety is a result of concentration
levels of the consumed element in its different
ionization states. Concentration levels are
dependent upon geologic processes that have
occurred in the past or are currently ongoing
these processes can be influenced and enhanced by
humans.
HEALTH CONCERNS There are various health
concerns related to scientifically recorded high
concentrations of geogenic arsenic. Significantly
high prevalence of skin cancer was observed in
all arsenicosis-endemic areas around the world.
(Centento et al, 2007) Squamous cell carcinoma,
rhagades and hyperkeratosis are a few of the skin
problems that have been the most noticeable
health complications caused by arsenic poisoning.
Inhalation of arsenic can occur near mining areas
and in places where the burning of coal is used
as an energy source. When arsenic becomes a
systemic toxicant it is known to induce
cardiovascular disease, neurobehavioral
disorders, and respiratory disorders, and various
cancers like liver and kidney. (Centneto et al,
2007) See Figures 4, 5, 7, 9
Figure 2. Different molecular configurations of
arsenic
Figure 10. Arsenic and other metal concentrations
in chilli peppers and corn.
SUMMARY 1. Arsenic is geogenic and can be found
at different ionization states throughout the
lithosphere. Geologic processes that have
influenced or currently do influence the area in
question determine the mobility of arsenic in the
groundwater and in the land. 2. Geogenic Arsenic
is found to be associated mostly with alluvial
and deltaic sedimentary deposits which contain
pyritic rock types. Arsenic is most commonly
associated with pyrite, which can be found in
clays and mud, and in environments where there
are high levels of iron oxides. 3. There are
various human health concerns related to exposure
of concentrated levels of As. The most commonly
found health degenerates are related to skin
disorders such as Hyperkeratosis, Bowens
Disease, hyper pigmentation, and various
cancers. 4. There are many cases of arsenic
poisoning world wide. In the Bengal Basin area,
the most severe cases are caused by exposure to
arsenic via groundwater, which is used for
drinking and irrigation. In China, chili peppers
are believed to be the main cause of exposure.
The Chinese population in this area uses
contaminated to coal to roast their chili peppers
for which are used for every day consumption.
Figure 11. Environmental Health Perspectives
Figure 1. Distribution of Arsenic Globally in
Oxidizing and Reducing Conditions
GEOLOGIC SOURCE, FATE, AND TRANSPORT OR ARSENIC
Arsenics mobility in the lithosphere is a
direct impact of the geologic setting it resides
in. Arsenic has different ways it mobilizes
through the environment. AS(III), Arsenite is
considerably more toxic than Arsenate, As(V)
because it is less soluble. (Naidu and Naderbaum,
2003) Pyrite is a type of rock that is formed
under sedimentary conditions, at low
temperatures, in reducing conditions. This type
of rock is found alluvial deposits, sediments of
rivers, lakes, oceans, and many aquifers. The
depth of sedimentary deposits affects the
concentrations of arsenic that occur. (Smedley
and Kinniburgh, 2005). Found in mud and clays,
pyrite is significant because it generally
contains high levels of As(V). Pyrite is unstable
in aerobic systems and undergoes which releases
iron oxides while it desorbs the previously
adsorbed arsenic. (Smedley and Kinniburgh, 2005)
Redox potential and pH are the most important
factors of arsenic speciation in aqueous systems.
( Smedley and Kinniburgh, 2005) Alluvial and
deltaic plains as well as large inland basins
are at a much greater risk to encounter high
arsenic concentrations because of their
interaction with aqueous environments. In
strongly reducing aquifers, typified by Fe(III)
and sulfate reduction, As(III) typically
dominates. ( Smedley and Kinniburgh, 2005) See
Figures 1, 2, 3
Figure 4. Keratosis on hands, 2008
Figure 5. Health Impact Visual
WEST BENGAL/BANGLADESH
Addressing population at risk, the West
Bengal/Bangladesh groundwater arsenic problems
are by far the most serious cases recorded world
wide. Approximately 35 million people, in the
West Bengal/Bangladesh area, are exposed to
levels of arsenic in their drinking water above
the US EPA recommendation of 0.10ppm and also
above the Indian recommendation for 0.05mg per
liter. The source of exposure is primarily from
potable water used for drinking and irrigation.
The Bengal Basin groundwater problems with
arsenic generally occur within young, mainly
Holocene, shallow aquifers(lt150m depth), composed
of alluvial and deltaic sediments deposited by
the vast river systems of the Ganges,
Brahmaputra, and Meghna (Smedley and
Kinniburgh, 2005) The lower parts of the basin
are covered in clays and fine silts these silts
are responsible for the widespread development of
reducing conditions. Concentrations range from
lt0.05 to around 3200µ per liter. (Smedley and
Kinniburgh, 2005) See Figures 3, 6, 8

References Cited Naidu, R., and Nadebaum, P.R.
Geogenic Arsenic and Associate Toxicity Problems
in the Groundwater-Soil-Plant-Animal-Human
Continuum. CSIRO Land and Water, 2001 Smedley,
Pauline, and Kinniburgh, David G. Arsenic in
Groundwater and The Environment. British
Geological Survey, 2005 Wuyi, Wang, et al.,
Mitigation of Endemic Arsencosis with Selenium
An Example in China. Institute of Geographical
Sciences and Natural Resources Research,
2003 Centeno, Jose A., Global Impacts of
Geogenic Arsenic A Medical Geology Research
Case. Royal Sweedish Sciences, 2007 Also see
www.wou.edu/rkeller06 for a more complete list
of references.