2. Brief History of Arsenic
Discovery
History is convoluted
Not sure who first discovered
Greeks and Romans had slaves mine for arsenic
Used in Alchemy
Albertus Magnus www.en.wikipedia.com
German chemist
First to isolate in 1250 AD
3. General Information of
Arsenic
Chemical Formula = As
Atomic Number = 33
Molecular Weight = 74.92 grams
Color = lead gray, gray, white
Hardness of 3.5
Similar to calcite or flourite
Talc is 1 and diamond is 10
Nonmagnetic
Metallic
Poor conductor of heat & electricity http://periodictable.com/Elements/033/index.html
4. Inorganic vs. Organic
Arsenic
Inorganic Organic
Occurs naturally in soil and many minerals
and ores that contain copper and lead Mainly found in marine organisms
When heated, arsenic rises up
smokestack as a fine dust Can still be used on agriculture
Cannot be used in agriculture Primarily cotton
Used to pressure treat wood Improve properties when added to
Arsenate V is found in water an allow or metal
Greatest use in lead acid batteries
Semiconductors and LED’s
Arsenate III found in water
http://www.finegardening.com/design/articles/pressure-treated-wood-in-beds.aspx
5. Uses of Arsenic
‘Poison of Kings’
Marsh and Reinsch Tests
Bronze alloy
Lead alloy
Medicinal uses
Syphili, yaws, psoriasis, and other viruses
Industrial uses
http://biologyze.com/tag/arsenic-and-bacteria/
Ammunition production, pigments, insecticides, rat
poison, wood preservative, semiconductors, & others
6. Environmental Sources of
Arsenic
Marine animals
In drinking water
~200 mineral species http://deepbluehome.blogspot.com/2010/10/deep-blue-home-
snapshot-2000-2010.html
Most common is arsenopyrite
Emitted from volcanoes
http://ebt2010.blogspot.com/2010/07/understand-whats-
arsenic-and-how-it.html
http://www.ecowaternorthwest.com/arsenic.php
7. Anthropogenic Sources of
Arsenic
Reduction of Arsenic Trioxide
(As2O3 - Arsenite) with charcoal
As2O3 is created during the metal
smelting process
Industrial uses http://www.ehow.com/how_6160537_preserve-pressure-treated-wood.html
Ammunition production,
pigments, insecticides, rat http://www.indiamart.com/alchemylaboratories
/analytical-reagents.html
poison, wood preservative,
semiconductors, & others
http://serc.carleton.edu/woburn/issues/pesticides.html
8. Mechanism
Inorganic
Arsenate – exists in +5 oxidation state
Arsenite – exists in +3 oxidation state
11. Mechanism (Continued)
In general, As terrorizes the metabolic processes of
the mitochondria
http://www.phschool.com/science/biology_place/biocoach/cellresp/overview.html
12. Mechanism (Continued)
Pentavalent toxicity
Very similar to phosphate
Can substitute for inorganic phosphate in glycolytic and
cellular respiration pathways
13. Mechanism (Continued)
Pentavalent toxicity
ADP-phosphate = ATP
ADP-arsenate = biologically useless
High energy phosphate bonds are lost
Stopping the production of ATP will stop all processes
that require ATP
14. Mechanism (Continued)
Trivalent toxicity
Reacts readily with thiol-containing molecules (-SH
functional group)
Amino acid cysteine contains thiol group
Cysteine rich proteins are vulnerable to As binding
but if binding does not have detrimental effects on
the protein, this may serve as a detoxification
mechanism
15. Mechanism (Continued)
Trivalent toxicity
Pyruvate Dehydrogenase (PDH)
requires lipoic acid cofactor – a dithiol
As inhibits this enzyme by binding to
the cofactor
The citric acid cycle cannot proceed
because the pathway is terminated
http://upload.wikimedia.org/wikipedia/commons/0/0b/Citric_acid_cycle_with_aconitate_2.svg
16. Mechanism (Continued)
Oxidative Stress
Reductase enzymes are present in the cell to reduce
reactive oxygen species (ROS)
As binds and inhibits some of these reductases, resulting
in the accumulation of ROS
ROS can bind/damage DNA and other cellular
components
Part of As carcinogenicity
17. Mechanism (Continued)
Carcinogenicity
Researchers have yet to fully elucidate carcinogenic
mechanisms of As
It is widely accepted that As is a carcinogen and several
mechanisms have been proposed
18. Mechanism (Continued)
Carcinogenicity
ROS accumulation
DNA Excision Repair and DNA Ligase inhibited by
Arsenic
Co-mutagenic effect with ROS, UV radiation, http://www.biol.unt.edu/~jajohnson/DNA_sequencing_process
X-Rays, and other chemicals
DNA methylation alterations
Also noted as a tumor promoter in mouse ovarian
cancers
19. Health Effects and
Symptoms
Acute As poisoning
Nausea
Vomiting
Blood in the urine
Cramping muscle
Hair loss
Stomach pain
Convulsions
Organ failure
Comma to death (interferes with glycolysis)
20. Health Effects and
Symptoms
Chronic arsenic poisoning
High oxidative stress
affect the structure of function of cardiovascular
system
Increases the risk of cancer
Vitamin A deficiency
Night blindness
Heart disease
Skin color change
Eye inflammation
Hyperkeratosis and hyperpigmentation http://wewinwater.com/2011/09/03/addressing-arsenic-poisoning-in-bangladesh/
Blushed complexion
21. Health Effects and
Symptoms
Bangladesh
77 million people (1/2 population of crowded
Bangladesh) may have been exposed to toxic levels of
arsenic.
More than 20% of deaths are caused by arsenic.
Groundwater is contaminated with As
http://www.who.int/topics/arsenic/en/
22. Health Effects and
Symptoms
United Kingdom (1990 and 1991)
In UK, 6000 people had the arsenic poisoning and 70 of
them died.
The beer contained 15ppm of arsenic
Glucose (ingredient of beer) is contaminated to
arsenic
Contaminated during the refining process
http://www.beer100.com/beercalories.htm
23. Health Effects and
Symptoms
Japan (1955)
In Japan, 12,130 children suffered from the arsenic
poisoning and 130 of them died.
Milk from Tokushima factory was contaminated to
arsenic
Symptoms
loss of appetite, vomiting, diarrhea, boil, skin color
changed to black, anemia, hypertrophy of the liver
Aftereffect http://romanianrecipes.wikia.com/wiki/Milk
blurred vision, hard of hearing, low score in school
record, abnormal brainwave, epilepsy, headache,
dizziness, cold hands and feet
24. Health Effects and
Symptoms
Arsenic and ADHD study (Roy et al 2010)
526 6-7 years old children in Torreon Mexico
Urinary arsenic levels were measured
No significant relationship found between any measure
of urinary arsenic and parents ratings of behavior
However, higher urinary arsenic was associated with
high scores on Cognitive Problem exams
25. Health Effects and
Symptoms
Pre- and Postnatal Arsenic Exposure and Body Size
– a cohort study (Saha et al 2012)
Purpose - to assess potential effects of early life As exposure on
weight and length of children from birth to 2 years of age
2372 children born in Bangladesh.
Measured arsenic concentrations in urine (U-As) with child
body weight and length
Compared to girls in the first quintile of U-As (<16 µg/L),
those in the fourth quintile (26-46 µg/L) were almost 300 g
lighter and 0.7 cm shorter.
Postnatal arsenic exposure was associated with lower body
weight and length among girls, but not boys.
26. Arsenic Regulation &
Legislation
EPA
Proposed a maximum contaminant level (MCL) of
5mcg/L in 2000 and established at 10mcg/L on Jan 22,
2001
This rule became enforceable on Jan 23, 2006
This standard protects public health based on the best
available science and ensures that the cost of the
standard is achievable
27. Arsenic Regulation &
Legislation
FDA
Currently only has a standard for maximum levels of As in
bottled water
No inorganic As regulations in Europe and U.S. in relation to
food
Only China has a regulatory limit (150 ppb)
Today, FDA is testing apple juice and trying to determine an
appropriate level
Apple juice containing >23 ppb of organic arsenic represent a
potential health risk
28. Arsenic Regulation &
Legislation
Organic Food
Organic food is not exempt from being contaminated by
toxic chemicals
Organic standard do not prohibit the presence of As
Two brands of organic infant formula – 20 times more
As than other regular brands
Institute for Agriculture and Trade Policy (IATP) and
FDA move toward regulating As contaminant levels in
the food supply
