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Health Effects Due to Arsenic
Exposure from Drinking Water
Neera Erraguntla, Ph.D.
Toxicology Section
Texas Commission on Environmental Quality
[email protected]
512-239-2492
Overview of Presentation
Basics
History
Forms of Arsenic
Inorganic vs. Organic
Mediums of Arsenic Exposure
Soil, Water, Food, and Air
Health Effects
Cancer vs. Non-Cancer
Conclusions
Q&A
What is Arsenic ?
Arsenic (As) is an element
– This means that it is a chemical that can’t be broken
down into simpler chemicals
Inorganic As is a human carcinogen (EPA, 1984)
As: A Global problem
200 million people worldwide are at risk to As exposure
(NRC, 2001)
Several regions in the World are above the WHO’s
maximum permissible limit. These include:
- Bangladesh
- Cambodia
- India
- Vietnam
- China
- Thailand
- Argentina
- U.S.
- Chile
- Nepal
- Mexico
- Ghana
- Taiwan
History
As linked to ancient migration:
As levels as high as 229 mg per kg
were found in the fossils near a deep
aquifer
“Perfect Poison” for Murder
– Popular with mystery writers
In France ~ 1000, children died.
They lived in rooms with wallpaper
containing Paris Green.
Arsine gas was the culprit
Where does As come from?
Natural:
– As occurs naturally & is widely distributed in the
Earth’s crust
– Volcanic activity, rock & mineral erosion, & forest fires
release As
– As is often concentrated in sulfide-bearing
mineral deposits (e.g., gold and copper)
– Strong affinity to pyrite (very abundant) and hydrous
iron oxides
As: Where does it come from?
Anthropogenic or Man-Made:
–
–
–
–
Drilling Wells
Mineral Extraction
Processing Wastes
Pesticides
Levels of As in water depend on:
– Level of human activity
– Distance from pollution sources
US EPA
The Safe Drinking Water Act (SDWA)
authorizes the USEPA to set national
health-based standards for drinking
water to protect humans against both naturally
occurring and man-made contaminants that may
be found in drinking water.
US EPA, states, and water agencies/divisions then
work together to make sure that these standards
are met for rivers, lakes, reservoirs, springs, and
groundwater wells.
Inorganic Forms of As
Inorganic arsenic compounds are used to preserve
wood
In the environment, As combines with oxygen,
chlorine, & sulfur to form inorganic compounds
Inorganic forms are toxic
Organic Forms of As
As in animals and plants combines with carbon
and hydrogen to form organic arsenic compounds
Organic arsenic compounds are used as pesticides,
primarily on cotton plants
Fish & shellfish can accumulate organic forms
(nontoxic)
As in the Environment
As can only change its form in the environment. It
cannot be destroyed.
As in air will settle to the ground or is washed out of
the air by rain
Many As compounds are easily solubilized in water
due to changes in pH and temperature
How might I be exposed to As ?
Eating food, drinking water, or breathing air
containing As
Breathing sawdust or burning smoke from wood
treated with As
Living near uncontrolled hazardous waste sites
containing As
Living in areas with unusually high levels of As in
rock
What Are the
Final Drinking Water Regulatory
Standards for Arsenic ?
• The enforceable Maximum Contaminant Level
(MCL) is
- 0.01 mg/L
-10 micrograms per liter (µg/L)
- 10 parts per billion (ppb)
Human Health Effects
• Exposure to As in drinking water is reported to
cause different human cancer and non-cancer
diseases
Non-Cancer Health Effects
Long-term As exposure was found to be associated
with cardiovascular effects (Utah and Taiwan)
As exposure has also been reported to cause
hypertension, anemia, liver disorders, kidney
damage, headache, & confusion.
Among children there have been reports of
intellectual impairment when As in drinking water
exceeded 50 µg/L (Bangladesh)
Non-Cancer Health Effects
Diabetes Mellitus: Dose-response relationship
between As exposure and Diabetes (Am. J.
Epidemiology)
Elevated risk of keratosis and Diabetes as a result of
long-term As exposure (Bangladesh)
Cancer Health Effects
Cancer: Long-term Exposure (20-40 yrs)
– Skin cancer (Taiwan)
– Keratosis and Hyperpigmentation
– Blackfoot Disease (Mainly Taiwan)
– Lung cancer (Taiwan, Japan, & Chile)
– Bladder cancer (Taiwan, Argentina)
– In a study conducted in the United States no reports of
bladder cancer with average 40 µg of As/L in a study
– In a case control study in conducted in Western United
States, it was found that smoking can elevate bladder
cancer risk when drinking water has As levels near 200
µg/day
Health Effects
Keratosis
Exposure Routes
As exposure can occur through food, water, air,
and medicines
Minimal exposure through air
Major exposure pathway is through diet
– Total Food intake : 50 µg As/Day; <4 µg As/day from
drinking water
Metabolism of As
Inorganic As upon ingestion is converted to two
“intermediate” compounds that are more toxic
than the parent compound (activation step)
These intermediates are more persistent and are
identified in the urine of individuals chronically
exposed to As in drinking water
Interindividual Variability
Differences in the genetic make up determines
whether an individual is susceptible to As
exposure
Differences in susceptibility to As can be due to
differences in age, sex, and nutritional status (e.g.
selenium can provide protection against diseases)
Infants and children more susceptible
Benefits of the New Rule
Reducing the arsenic MCL from 50 µg/L to 10 µg/L
will help reduce Arsenic exposure to approximately 13
million Americans
Prevent ~19-31 theoretical cases of bladder cancers
per year & ~5-8 theoretical cases of deaths due to
bladder cancer per year
Prevent ~19-25 theoretical cases of lung cancers &
~16-22 theoretical cases of deaths due to lung cancer
per year
Reduce potential non-cancer effects
Conclusions
• Public Health Can Be Severely Impacted by
presence of elevated levels of As in drinking
water
– in mortality & morbidity
– Everyone is vulnerable
– Degrees of vulnerability depend on
Biological susceptibility
Exposure & dose
• There Are Safe Levels Below Which No
Adverse Health Effects Occur
Take Home Message
• Collectively, we can achieve sufficient
reductions to protect public health
• We can limit exposure, especially of susceptible
populations
–
–
Pregnant women
Children