Arsenic toxicity

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2. Arsenic
Presented by:
Fatima Qaiser 4 M
Quratulain 17 M
Fasiha Shahbaz 27 M
Amina Amanat 34 M
Presented to:
Sir Dr. Naeem Akhtar Abbasi

3. Objectives……
History
Chemistry
Ores
Sources
Pathways to enter in Enviroment
Human exposure and its Health effects
Remedial measures
Risk assessment
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4. Brief History :
• Discovered by Albertus
Mangus ,he heated a common
compound of arsenic,
(orpiment with soap and form
the pure form of arsenic.
in1250AD
• Get its name from a persian
word for yellow pigment
orpiment and a latin word
arsenicum.
• In ancient times it was used as
poisons of kings.
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5. Arsenic Chemistry:
 Symbol = As (group 5A)
 Atomic no = 33
 Molecular weight = 74.92g
 density = 5.7gcm3
 Hardness = 3.5
 Melting point = 814C
 Boiling point = 615C
 Color = silver grey
 Allotropic form = yellow, black and
grey
 Oxidation state = 0, -3,+3, +5
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6.  Non-magnetic and is a crystalline metal.
 Poor conductor of heat and electricity.
 Hardly convert into water soluble products.
 Tarnishes in air forming arsenic trioxide.
 Arsenic gas AsH3 is most dopant gas n microchip industry.
 Arsenic alloys used in car batteries.
 As2O3 used as fowler solution.,for manufacturing paints.
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7. Limitations and standards for Arsenic:
(WHO and OSHA)
WHO
Daily
Intake
Drinking
water
Air
3.0
ugkgday
10ugl
Cannot be
established
OSHA
Water
Air
Action
level
10UGL
10UG
M3
5UG
M3
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8. Ores of arsenic:
Arcinopyrite (FeAsS)
Orpiment (As2S3)
Realgar (As2S2)
With oxygen (As2O3),(AsO5),(As2O4)
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Sources of Arsenic
Natural:
 Arsenic occurs naturally in the earth’s crust.
 Volcanic activity, rock and mineral erosion and Forest Fires
release Arsenic in the environment.
 As is often concentrated in the sulphide-bearing mineral
deposits e.g.; gold and cobalt.
Anthropogenic:
 Reduction of Arsenic Trioxide with charcoal.
 Arsenic trioxide is also produced during smelting process of
ores like lead, nickel, zinc etc.
 Industrial uses includes Ammunition production, pigments,
Insecticides, rat poison, wood preservative, semiconductors
and others.
 In 19th century, Arsenic was used in paints and dyes for
clothes, paper and wallpaper.

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How Arsenic gets into water?
 Naturally low concentration, in inorganic form (arsenite and
arsenate)
 Geological formations
 Geothermal and volcanic activity
 Weathering of rocks, oxidative dissolution of arsenic bearing
minerals releases arsenic in the water
 Anthropogenic sources of surface water contamination with
arsenic includes industries
 Indirect sources include pesticide and fungicide runoff from
fields
 Arsenic gets in the ground water because of the geology of
that area
 By the infiltration of snowmelt/rain water containing arsenic
residues
 Majority of the ground water contains arsenate (pentavalent
form)

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How Arsenic get into soil?
 Arsenic in soil is mostly in inorganic form
 Pentavalent form (arsenate) dominates in the soil
 because of oxidation of trivalent arsenicals.
 Arsenic in soils are mostly present in sulfide ores of
metals from the weathering of the parent rock
(sedimentary)
 Anthropogenic activities like use of pesticides,
herbicides and fertilizers can introduce arsenic in soil.
 Solubility and mobility of arsenic depends on the
chemical form of arsenic.
 Arsenate is typically less mobile in soil, and arsenite is
more mobile;
 Organic arsenic compounds are less mobile
 Greater the aluminum and iron compounds in the soil,
greater will be the arsenic content

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How Arsenic get into Air?
 In air, arsenic exists attached to particulate matter,
as a mixture of arsenite and arsenate
 Most of the inorganic arsenic in the atmosphere is
trivalent and Pentavalent
 Human exposure to arsenic through air occurs at
 concentrations as low as 0.4 to 30 ng/m3
 Majority of air emission is arsenic is from
industrial
 Areas.
 Coal combustion for thermal power plants is one
of
 the major sources of anthropogenic arsenic
 emission into the biosphere.

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15. Human exposure
The main routes of human exposure of arsenic are through
 Ingestion
 Inhalation
 Dermal Contact
People are most likely exposed to inorganic arsenic through drinking
water. This is especially true in areas with water sources that naturally
have higher levels of inorganic arsenic. People can also be exposed to
inorganic arsenic by eating such foods as rice and some fruit juices.
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16. Human health Effects
Long-term exposure to arsenic from drinking water and food can cause
 cancer
skin lesions
cardiovascular disease
Diabetes
 In utero and early childhood
exposure has been linked to negative
impacts on cognitive development and
increased deaths in young adults.
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18. Remedial measures
The remedial measures includes variety of options, ranging from
 removing arsenic from ground water after it is extracted
 searching alternative aquifers
 reducing the level within the aquifer itself
 dilution of the contaminants by artificial recharge
 blending with potable water
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19. Health risk assessment of
arsenic in drinking
groundwater: A case study
in a central high land area
of Vietnam

20. Introduction
• Worldwide, million people are exposed to arsenic due to using As-
contaminated groundwater for daily needs
• The current recommended limit of arsenic in drinking-water is 10
μg/L.
• As groundwater is very important sources for drinking and irrigation
purposes, million of people could be exposed to As.
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21. Study Area
District of Lam dong
province
• Cat tien
• Da the
• Da houai
• Bao loc
hydrogeology
• Seven types of aquifer:
• Holocene
• Neogene
• Pleistocene basalt rock
• Pliocene sedimentary
rocks.
Wells
• Dug well (shallow
depth )
• Drilled well (deep
aquifers )with 70m
depth
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23. Collection of dataset
Department of
natural
resources and
environment
environment
188 samples
from private
wells
As conc
&PH
Type
,location
& depth
Water
treatme
nt tools
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24. Health risk assessment
The risk assessment for human health of As in groundwater through drinking and
domestic purposes for two groups of residents: children and adults.
Where:
 ADD is average daily dose from ingestion (mg/kg/day);
 C is arsenic content in groundwater samples (mg/L);(H:500 ug/L)(L: 5 ug/L dug well)
 IR is water intake rate, 1 L/day for children and 2 L/day for adults
 EF is exposure frequency (365 days/year);
 ED is exposure duration, 10 years for children and 70 years for adults.
 AT is the averaging time for carcinogenic exposure, 3,650 days for children and 25,550
days for adults. BW is the body weight that equals 10 kg for children and 55 kg for
adults.
ADD=(C×IR×EF×ED)/(AT×BW) (1)
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25. Non carcinogenic risk
hazard quotient is calculated as equation
HQ=ADD/RfD
 HQ is hazard quotient (unitless),RfD is the reference dose (0.0003
mg/kg/day)
The carcinogenic risk (CR) is calculated as equation:
CR=CSF×ADD
 CSF is the cancer slope factor for arsenic (1.5 mg/kg/day),The highest safe
standard for carcinogenic risk is 10-4
Carcinogenic Risk
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26. Results
• Arsenic concentration generally observed when pH of groundwater is
from 6 to 8.
• The As concentration in groundwater collected from drilled wells
(average of 54 ug/L) are much greater than in dug wells (average of 5
ug/L). The highest concentration of As is observed in the well depth of
40 and 60 m below land surface.
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28. Conclusion:
Lam Dong province with the highest contaminated level of
500g/L, 50 times higher than the WHO guidelines. 11.7%
of total (n=188) samples exceeded the drinking water limit
for As 10 ug/L.u10 ug/Lg/L).
The health risk assessment showed that 25.5% and 29.3%
of the carcinogenic risk values for adults and children
exceeded the highest acceptable level value of (10-4)
proposed by US EPA
The dataset also indicated that 93% of surveyed wells, the
groundwater was pumped directly without any treatment and 7%
of wells, pumped groundwater was simply treated by sand
filtering. This way of using groundwater is unsafe for human
health.
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