Context - Arsenic is a poisonous substance, which is released both from certain human activities and naturally from the Earth's crust.
Humans may be exposed to arsenic mainly through food and water, particularly in certain areas where the groundwater is in contact with arsenic-containing minerals.
To what extent can arsenic exposure affect human health or the environment?
Latest update: 15 December 2004
1. What is arsenic?
Arsenic is a natural element
which behaves like a metal. It is present in the environment both
naturally and due to certain human activities. It has many different
forms. It can exist in inorganic or
inorganic arsenic being generally
considered more toxic.
Arsenic can be measured by a variety of laboratory methods. Some of
these can distinguish between different forms of arsenic and some
methods allow very small amounts to be measured accurately.
2. Where does environmental arsenic come from?
Arsenic is found in the natural environment in some abundance in the
Earth’s crust and in small quantities in rock, soil, water and air. It
is present in many different minerals. About one third of the arsenic in
the atmosphere comes from natural sources, such as volcanoes, and the
rest comes from man-made sources. Due to natural geological
contamination, high levels of arsenic can be found in drinking water
that has come from deep drilled wells. This is particularly true for
Industrial processes such as mining, smelting and coal-fired power
plants all contribute to the presence of arsenic in air, water and soil.
Environmental contamination also occurs because it is used in
agricultural pesticides and in chemicals for timber preservation.
Arsenic occurs in different forms and some is transported between
different parts of the environment where it may change its form. Arsenic
in weathered rock or soil can be picked up and moved by the wind and
water. Many arsenic compounds bind to soil and only move short distances
when water percolates down through the soil. If arsenic is released into
the atmosphere by industrial processes or volcanic activity, it attaches
to particles that are dispersed by the wind and fall back to the ground.
Microbes in soil and sediment also release substances containing arsenic
into the atmosphere. These are then converted to other arsenic compounds
that settle back onto the ground.
3. What are the levels of exposure to arsenic?
Environmental levels of arsenic vary. In air, levels are lowest in
remote and rural areas, higher in urban areas, and highest close to
industrial sources. In water, levels of arsenic are lowest in seawater,
higher in rivers and lakes and highest in water from underground areas
containing volcanic rock or arsenic-rich mineral deposits. The
background levels of arsenic in
soil and sediment increase if there are natural and/or man-made sources
of arsenic contamination present.
The amounts of arsenic found in living animals, plants and microbes
vary. The quantities depend on the level of local contamination and on
the type of organism, as certain organisms tend to
accumulate arsenic in their bodies.
Arsenic is generally present in sea-living animals at higher levels than
in freshwater animals, or plants and animals that live on land. Plants
on land can accumulate arsenic compounds via uptake from soil and/or
deposition from air onto leaves.
Humans are exposed mainly through
food and water. Food is usually the largest source except in areas where
drinking water is naturally contaminated with arsenic. The quantities of
arsenic breathed in by non-smokers are very small, except in
industrially polluted areas. Smokers
inhale more because arsenic is one of
many hundreds of chemicals present in cigarette smoke.
Exposure to arsenic in the workplace
can be quite high, but the amounts present in the air in the workplace
are controlled in many countries.
4. What happens to arsenic in the body?
When arsenic is inhaled due to its
presence in airborne particles, the amount
absorbed into the blood stream
depends on two things – how soluble
the particular form of arsenic is and how small the particles are. This
said, most arsenic in the body comes from the diet. In the gut, soluble
arsenic compounds present in food are rapidly absorbed into the blood
stream. Many arsenic compounds are quickly transformed and eliminated
from the body via the urine. However, there are differences from one
person to another in the ability to get rid of arsenic compounds.
The amount of arsenic in the body can be estimated by taking samples
of blood, urine, hair, or nails and measuring the arsenic - or
arsenic-containing substances - present. Arsenic disappears rapidly from
blood, so measurements in blood only tell you about recent high
exposures, such as poisonings, or
long-term exposures if they are repeated and high. Levels in urine are
the best measure of recent exposure,
whereas levels in hair and nails can tell you about past
5. What are the effects of arsenic on laboratory animals?
Arsenic can have adverse effects on laboratory animals but some forms
of arsenic are more toxic than
others. The consequences include death when
exposures are high enough to cause
poisoning and cancer. Many parts of
the body may also be damaged by arsenic, including the skin, gut, lungs,
heart, blood vessels,
immune system, urinary system,
reproductive organs and the nervous system. Arsenic can also damage
chromosomes, which contain the
genetic material inside the cells
of the body.
6. What are the effects of arsenic on the environment?
Living organisms, both on land and in water, react in a variety of
ways to arsenic exposure. The effects
depend on the chemical form of the arsenic, the nature of the
surrounding environment and their own particular biological sensitivity.
Individual organisms or whole populations may be affected. Adverse
effects include death, poor growth and failure to reproduce. Where
arsenic has contaminated a natural environment, the number of different
species found is much reduced.
7. What are the effects of arsenic on human health?
If a large amount of arsenic is swallowed by humans, in a form that is
readily absorbed, it can cause rapid
poisoning and death. The gut, the heart and the nervous system are
affected. Those who survive acute poisoning may develop
pigment spots in the skin and
damage to red blood cells, bone
marrow (where blood cells are made), liver, nerves and brain. Long-term
exposure to high levels of arsenic in
drinking water can cause thickening and pigment spots in the skin, and
cancer of the skin, lungs, bladder
or kidney. Exposure in the workplace – mainly via the air breathed in –
can cause lung cancer. Smoking further increases the
Long-term ingestion of arsenic,
mainly from drinking of contaminated well water, has caused a disease
called "blackfoot disease" in
Taiwan. Blood vessels of the leg and foot become damaged, resulting in
coldness, loss of feeling and eventually gangrene in the foot.
8. What has happened in areas where drinking water is heavily contaminated?
Drinking water from unpolluted sources normally contains only small
amounts of arsenic. Drinking water from underground wells can become
heavily contaminated in certain areas where the
groundwater is in contact with
natural arsenic from minerals. This can be a serious problem in
countries like Bangladesh, West Bengal in India, and Taiwan. In
Bangladesh, large numbers of people are regularly drinking water
containing more than 5 times and up to more than 100 times the usual
concentration of arsenic. Adverse
effects on health, such as skin changes and
cancer have been experienced by
people living in these regions.
9. What have WHO and IARC established about arsenic?
International bodies have previously evaluated arsenic: the World
has set a provisional guideline value of 10 µg/litre for arsenic in
drinking-water and according to the International Agency for Research on
there is enough evidence to
conclude that “arsenic and arsenic compounds”
can cause cancer in humans.
Arsenic is a chemical substance, which is released from the Earth’s crust via
natural processes and from certain human activities. It can exist in
inorganic arsenic being generally
considered more toxic. (see 1.
Environmental levels of arsenic
vary. Concentrations of the generally more toxic
inorganic arsenic are highest in air close
to industrial sources, in underground water
in areas with natural geological contamination, and in soils or sediments near
contamination sources. Concentrations of the less toxic
organic arsenic are particularly high in
sea-living animals and therefore in seafood.
Humans are exposed
mainly through food and water, but arsenic can also be
absorption into the blood stream, arsenic is
rapidly transformed and eliminated from the body via urine. (see 3.
Organisms living in the environment
react in a variety of ways to arsenic
exposure. It can even lead to death, poor
growth and failure to reproduce. Where arsenic has contaminated a natural
environment, the number of different species found is reduced. (see 5.
In humans, if a
large amount of the more toxic
inorganic arsenic is swallowed in a form
that is readily absorbed, it can affect the
gut, the heart and the nervous system, causing rapid poisoning and death.
Drinking water from unpolluted sources normally contains only small amounts of
arsenic. However, in areas with natural geological contamination, such as
Bangladesh, drinking water from wells can contain high levels of inorganic
arsenic; such levels can harm the skin and
are associated with increased
risk of cancer in the skin, lungs, bladder
and kidney. Exposure to contaminated air at
the workplace can cause lung cancer. (see 7.
Arsenic and arsenic compounds have been classified as
carcinogenic to humans and guideline values
for drinking-water have been set.