Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollutants, the components of pollution, can be either foreign substances or naturally occurring contaminants. Pollution is classed as point source or nonpoint source. There are many types of ocean pollutants that endanger ocean life. Some of them are more obvious than others, but all contribute to an unhealthy ocean and many times, the death of its creatures

1. Toxic Pollutants- Dioxins
Presented By
Abu Khairul Bashar
Roll No: 584
Session: 2011-2012

3. Introduction
Pollution is the introduction of contaminants into the natural
environment that cause adverse change. Pollutants, the components of
pollution, can be either foreign substances or naturally occurring
contaminants. Pollution is classed as point source or nonpoint source.
There are many types of ocean pollutants that endanger ocean life.
Some of them are more obvious than others, but all contribute to an
unhealthy ocean and many times, the death of its creatures.

4. Continuous…….
Toxic materials have the side effects on living organisms. Dioxins are
environmental pollutants. Dioxin is a general name for a large group
of chemical compounds with similar structure. These compounds are
made up of carbon, oxygen, hydrogen and chlorine atoms. The most
toxic dioxin has four chlorine atoms in positions 2, 3, 7 and 8. This
dioxin (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin) is often referred to as
TCDD or “dioxin”. TCDD is the most studied and the most toxic of
all dioxins.

5. Toxicological Properties
There is a large number of literature on dioxins. The available data
show that it is difficult to discuss the environmental characteristics
and risks of dioxins in general terms, basically because of 4 essential
complicating factors.
 Dioxins are in fact a large, heterogeneous group of chemicals. The
differences between congeners, with respect to environmental
characteristics such as ecotoxicity, bioaccumulation and
environmental fate and therefore the associated risks, can be very
large.

6. Continuous…..
 Most of the dioxin congeners are very hydrophobic. The
hydrophobic nature is a complicating factor in studying the
environmental characteristics. Regular ecotoxicity tests for
instance, are designed for water-soluble compounds. By using
additional solvents, concentrations in the test medium can lead
to ecological levels. This has resulted in a number of data on
dioxins, which are not suitable for risk assessment.

7. Continuous…
 In fact a similar problem occurs in determining the toxicity to
humans, where high doses used in animal testing make it
extremely difficult to estimate the risks at very low concentrations
as found in the environment .
 A large part of the body of evidence was generated for the 2,3,7,8
TCDD congener which is regarded as the most toxic one, but
which is not the environmentally most relevant one.

8. Sources of Dioxin Contamination
 Dioxins are mainly by products of industrial processes.
 But can also result from natural processes, such as volcanic
eruptions and forest fires.
 Dioxins are unwanted by products of a wide range of
manufacturing processes including smelting, chlorine
bleaching of paper pulp and the manufacturing of some
pesticides and herbicides .

9. Continuous….
 In terms of dioxin release into the environment, uncontrolled
waste incinerators (solid waste and hospital waste) are often the
worst culprits, due to incomplete burning.
 The highest levels of these compounds are found in some soils,
sediments and food, especially dairy products, meat, fish and
shellfish.
 Very low levels are found in plants, water and air.

10. Figure: Dioxin and Furan Emissions Trends 1990 – 2010, Excluding Natural Sources

11. Effects of Dioxins on Human Health
Short-term exposure of humans to high levels of dioxins may result
in skin lesions and altered liver function.
Long-term exposure is linked to impairment of the immune system,
the developing nervous system, the endocrine system and
reproductive functions.
Chronic exposure of animals to dioxins has resulted in several
types of cancer.

12. Continuous….
 TCDD does not affect genetic material and there is a level of
exposure below which cancer risk would be negligible.
 Due to the omnipresence of dioxins, all people have background
exposure and a certain level of dioxins in the body, leading to the
body burden.
 Current normal background exposure is not expected to affect
human health on average.

13. Continuous…
 The newborn, with rapidly developing organ systems, may be
more vulnerable to certain effects.
 Some individuals or groups of individuals may be exposed to
higher levels of dioxins because of their diets or their occupations
.
Human concentrations are much less, 10-100 pg/g.

14. Figure: Contamination in different parameter

15. Environmental Persistence and Bioaccumulation
All groups of dioxin-like compounds are persistent in the
environment. Ultraviolet light is able to slowly break down these
compounds. Lipophilicity and very poor water solubility make these
compounds move from water environment to living organisms having
lipid cell structures. This is called bioaccumulation. Increase in
chlorination increases both stability and lipophilicity.

16. Continuous….
The compounds with the very highest chlorine numbers are so poorly
soluble that this hinders their bioaccumulation. Bioaccumulation is
followed by biomagnification. Lipid soluble compounds are first
accumulated to microscopic organisms such as phytoplankton .
Phytoplankton is consumed by animal plankton, this by invertebrates
such as insects, these by small fish, and further by large fish and seals.
At every stage, the concentration is higher, because the persistent
chemicals are not "burned off" when the higher organism uses the fat
of the prey organism to produce energy. Due to bioaccumulation and
biomagnification, the species at the top of the trophic pyramid are
most vulnerable to dioxin-like compounds.

17. Figure: Dioxin is released into the environment and builds up in sediment

18. Prevention and Control of Dioxin Exposure
Proper incineration of toxic material is the best available method
of preventing and controlling exposure to dioxins. It can also
destroy PCB-based waste oils.
Prevention or reduction of human exposure is best done via
source-directed measures.
Strict control of industrial processes to reduce formation of dioxins
as much as possible.

19. Continuous…
More than 90% of human exposure to dioxins is through the food
supply, mainly meat and dairy products, fish and shellfish.
Good controls and practices during primary production, processing,
distribution and sale are all essential to the production of safe food.
Food contamination monitoring systems must be in place to ensure
that tolerance levels are not exceeded.
It is the role of national governments to monitor the safety of food
supply and to take action to protect public health.

20. Figure: Danger Dioxin Waste in waste box.

21. WHO Activities Related to Dioxins
Reducing dioxin exposure is an important public health goal for
disease reduction, also with respect to sustainable development. In
order to give guidance on acceptable levels of exposure.
 WHO has held a series of expert meetings to determine a tolerable
intake of dioxins to which a human can be exposed throughout life
without harm.
 In 2001, WHO Expert concluded that a tolerable intake could be
established for dioxins on the basis of the assumption that there is
a threshold for all effects, including cancer.

22. Continuous..
 WHO is now working with the United Nations Environmental
Programme (UNEP) on the implementation of the ‘Stockholm
Convention’, an international agreement to reduce emissions of
certain persistent organic pollutants (POPs), including dioxins.
 The experts established a tolerable monthly intake of 70
picogram/kg per month. This level is the amount of dioxins that
can be ingested over lifetime without detectable health effects.

23. Continuous…
 Since 1976, WHO has been responsible for the Global
Environment Monitoring System’s Food Contamination
Monitoring and Assessment Programme, provides information on
levels and trends of contaminants in food through its network of
participating laboratories in over 70 countries around the world.
Dioxins are included in this monitoring programme.
 Since 1987, WHO has conducted periodic studies on levels of
dioxins in human milk, mainly in European countries. These
studies provide an assessment of human exposure to dioxins from
all sources.

24. Continuous…
 During the last 15 years, WHO, through the International
Programme on Chemical Safety (IPCS), has established toxic
equivalency factors (TEFs) for dioxins and related compounds
through expert consultations. WHO-TEF values have been
established which apply to humans, mammals, birds and fish.
 The last such consultation was held in 2005 to update human
TEFs. These international TEFs have been developed for
application in risk assessment and management, and have been
adopted formally by a number of countries including Canada,
Japan, the United States and the European Union.

25. Conclusion
Dioxins occur as a complex mixture in the environment and in food.
In order to assess the potential risk of the whole mixture, the concept
of toxic equivalence has been applied to this group of contaminants.
TCDD, the most toxic member of the family, is used as reference
compound and all other dioxins are assigned a toxic potency relative
to TCDD, based on experimental studies.

26. Thanks All