Environmental toxicology

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Environmental Toxicology
Submitted To
Respected Mam Dr. Rabi Yaqoob
Submitted By
M Imran Ul haq
Roll Number
MCF1900758
Class MSc Zoology 4th
Semester
University of education Lahore (FSD Campus)

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1 Identify any toxicant you are exposed to in your daily routine
2 Mode of entry of body
3 Mode of action
4 Source of dioxin
5 Effects of dioxins on human health
6 Suggests a valid management action to deal with that toxicants
Sr.# Table of Content Page#

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Key facts
• Dioxins are a group of chemically-related compounds that are persistent environmental
pollutants (POPs).
• Dioxins are found throughout the world in the environment and they accumulate in the
food chain, mainly in the fatty tissue of animals.
• More than 90% of human exposure is through food, mainly meat and dairy products,
fish and shellfish. Many national authorities have programmes in place to monitor the
food supply.
• Dioxins are highly toxic and can cause reproductive and developmental problems,
damage the immune system, interfere with hormones and also cause cancer.
• Due to the omnipresence of dioxins, all people have background exposure, which is not
expected to affect human health. However, due to the highly toxic potential, efforts
need to be undertaken to reduce current background exposure.
• Prevention or reduction of human exposure is best done via source-directed measures,
i.e. strict control of industrial processes to reduce formation of dioxins.
1. Dioxins
Dioxins are a group of highly toxic chemical compounds that are harmful to health. They can
cause problems with reproduction, development, and the immune system. They can also disrupt
hormones and lead to cancer. Known as persistent environmental pollutants
(POPs), dioxins can remain in the environment for many years. Dioxin, also
called polychlorinated dibenzodioxin, any of a group of
aromatic hydrocarbon compounds known to be environmental pollutants that are generated as
undesirable by-products in the manufacture of herbicides, disinfectants, and other agents. In
popular terminology, dioxin has become a synonym for one specific dioxin, 2,3,7,8-
tetrachlorodibenzo-para-dioxin (2,3,7,8-TCDD).

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Background
Dioxins are environmental pollutants. They belong to the so-called “dirty dozen” - a group of
dangerous chemicals known as persistent organic pollutants (POPs). Dioxins are of concern
because of their highly toxic potential. Experiments have shown they affect a number of organs
and systems.
Once dioxins enter the body, they last a long time because of their chemical stability and their
ability to be absorbed by fat tissue, where they are then stored in the body. Their half-life in
the body is estimated to be 7 to 11 years. In the environment, dioxins tend to accumulate in the
food chain. The higher an animal is in the food chain, the higher the concentration of dioxins.
The chemical name for dioxin is: 2,3,7,8- tetrachlorodibenzo para dioxin (TCDD). The name
"dioxins" is often used for the family of structurally and chemically related polychlorinated
dibenzo para dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Certain dioxin-
like polychlorinated biphenyls (PCBs) with similar toxic properties are also included under the
term “dioxins”. Some 419 types of dioxin-related compounds have been identified but only
about 30 of these are considered to have significant toxicity, with TCDD being the most toxic.
Dioxin contamination incidents
Many countries monitor their food supply for dioxins. This has led to early detection of
contamination and has often prevented impact on a larger scale. In many instances dioxin
contamination is introduced via contaminated animal feed, e.g. incidences of increased dioxin
levels in milk or animal feed were traced back to clay, fat or citrus pulp pellets used in the
production of the animal feed,
Some dioxin contamination events have been more significant, with broader implications in
many countries.
In late 2008, Ireland recalled many tons of pork meat and pork products when up to 200 times
the safe limit of dioxins were detected in samples of pork. This led to one of the largest food
recalls related to a chemical contamination. Risk assessments performed by Ireland indicated
no public health concern. The contamination was traced back to contaminated feed.

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In 1999, high levels of dioxins were found in poultry and eggs from Belgium. Subsequently,
dioxin-contaminated animal-based food (poultry, eggs, pork) were detected in several other
countries. The cause was traced to animal feed contaminated with illegally disposed PCB-based
waste industrial oil.
Large amounts of dioxins were released in a serious accident at a chemical factory in Seveso,
Italy, in 1976. A cloud of toxic chemicals, including TCDD, was released into the air and
eventually contaminated an area of 15 square kilometres where 37 000 people lived.
Extensive studies in the affected population are continuing to determine the long-term human
health effects from this incident.
TCDD has also been extensively studied for health effects linked to its presence as a
contaminant in some batches of the herbicide Agent Orange, which was used as a defoliant
during the Vietnam War. A link to certain types of cancers and also to diabetes is still being
investigated.
Although all countries can be affected, most contamination cases have been reported in
industrialized countries where adequate food contamination monitoring, greater awareness of
the hazard and better regulatory controls are available for the detection of dioxin problems.
A few cases of intentional human poisoning have also been reported. The most notable incident
is the 2004 case of Viktor Yushchenko, President of the Ukraine, whose face was disfigured
by chloracne.
Chemical characteristics and production
The family of dioxins is characterized chemically by the presence of two benzene rings
connected by a pair of oxygen atoms. Each of the eight carbon atoms on the rings that are not
bonded to oxygen can bind with hydrogen atoms or atoms of other elements. By convention
these positions are assigned the numbers 1 through 4 and 6 through 9. The more toxic dioxins
carry chlorine atoms at these positions, and the best-known one has chlorine atoms at the 2,3,7,
and 8 positions. This isomer—2,3,7,8-TCDD—is extremely stable chemically. It is virtually
insoluble in water and in most organic compounds but is soluble in oils. It is this combination

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of properties that allows this dioxin in soil to resist dilution with rainwater and causes it to seek
and enter fatty tissue in the body if it is absorbed.
Dioxin serves no useful purpose but is formed as an undesirable by-product during the
synthesis of 2,4,5-trichlorophenol and some other useful compounds. The chemical 2,4,5-
trichlorophenol serves as a raw material for making the herbicides Silvex (fenoprop) and 2,4,5-
T (2,4,5-trichlorophenoxyacetic acid). The latter is a major active ingredient of Agent Orange,
a defoliant formerly used in Vietnam by the U.S. military and in the United States to kill
unwanted vegetation. This 2,4,5-trichlorophenol is used in the production of hexachlorophene,
an antibacterial agent formerly used in deodorants and soaps.
2. Main source of dioxin
Dioxin is formed by burning chlorine-based chemical compounds with hydrocarbons.
The major source of dioxin in the environment comes from waste-burning incinerators of
various sorts and also from backyard burn-barrels.
Consumption of potentially contaminated foods, such as beef and dairy products, is the primary
route for dioxin entry into the human body. In fact, more than 90 percent of human
dioxin exposure is attributed to dietary ingestion. Dioxins also can enter your body through the
air you breathe or by skin contact. Persons who burn household waste may come into contact
with dioxins in the ash, soil, gas or smoke. Agricultural workers using pesticides or solvents
may be exposed to dioxins. Dioxins are found throughout the world in the environment and
they accumulate in the food chain, mainly in the fatty tissue of animals. More than 90% of
human exposure is through food, mainly meat and dairy products, fish and shellfish.

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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 herbicides and pesticides. 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. Technology is available that allows for controlled
waste incineration with low dioxin emissions.
Although formation of dioxins is local, environmental distribution is global. Dioxins are found
throughout the world in the environment. 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.
Extensive stores of PCB-based waste industrial oils, many with high levels of PCDFs, exist
throughout the world. Long-term storage and improper disposal of this material may result in
dioxin release into the environment and the contamination of human and animal food supplies.
PCB-based waste is not easily disposed of without contamination of the environment and
human populations. Such material needs to be treated as hazardous waste and is best destroyed
by high temperature incineration in specialised facilities.
3. Mode of entry in Body
Dioxins also can enter your body through the air you breathe or by skin contact. Persons who
burn household waste may come into contact with dioxins in the ash, soil, gas or smoke.
Agricultural workers using pesticides or solvents may be exposed to dioxins. TCDD’s toxicity
is derived from the chemical’s ability to bind to a receptor protein known as the aryl
hydrocarbon receptor, which is present inside certain cells within the body. The resulting
TCDD-receptor complex can enter the cell’s nucleus and bind with its DNA, thereby
disrupting the cell’s machinery for producing proteins. The wide and rather puzzling array of
toxic effects induced in animals by high levels of TCDD are apparently all receptor-mediated
responses to the chemical. Such animals’ immune systems are those most often affected, being
apparently weakened or compromised by TCDD.

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Accumulation in the food chain
Dioxins are of particular concern in regard to environmental and human health because they
are persistent environmental pollutants and therefore accumulate within the food chain.
Because of their lipophilic properties, the chemicals are readily absorbed into fatty tissue, and
thus they have a tendency to accumulate in animals—for example, in fish, as a result of the
chemicals’ presence in aquatic environments, and in cattle and other livestock, as a result of
the chemicals’ release into terrestrial environments. Consumption of potentially contaminated
foods, such as beef and dairy products, is the primary route for dioxin entry into the human
body. In fact, more than 90 percent of human dioxin exposure is attributed to dietary ingestion.
Once in the human body, dioxins are absorbed into fat cells, where they persist for long periods
of time; the half-life of dioxin in humans has been estimated to be between 7 and 11 years.
The incineration of dioxins generated as by-products in manufacturing processes is an effective
method for controlling the release of the chemicals into the environment.
4. Mode of action:
Mechanism of action of dioxin-type chemicals, pesticides, and
other xenobiotics affecting nutritional indexes
Dioxins are highly toxic and can cause reproductive and developmental problems, damage the
immune system, interfere with hormones and also cause cancer. Due to the omnipresence
of dioxins, all people have background exposure, which is not expected to affect human health.
5. Toxicity in humans
The recognition in the early 1980s that residential sites at Times Beach and elsewhere
in Missouri, U.S., had been contaminated by improper disposal of chemical wastes containing
2,3,7,8-TCDD led to intense public scrutiny of its possible toxic effects. Toxicologists
concluded from studies on laboratory animals that TCDD is a persistent toxin, and they
recommended that soil levels in excess of one part per billion might constitute a health risk to

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humans. Animal studies indicated that human exposure to the chemical might be associated
with muscular dysfunction, inflammation, impotence, birth defects, genetic mutations,
and nervous system disorders. Those investigations also suggested a potential link between
exposure to TCDD and the development of various cancers in humans.
Although the actual physiological effects of TCDD toxicity in humans remain a matter of
debate, in 1997 the International Agency for Research on Cancer (IARC) upgraded the
classification of TCDD from a Group 2B possible carcinogen (cancer-causing substance) in
humans to a Group 1 known carcinogen in humans. The upgrade came after consideration of
extensive epidemiological studies of TCDD carcinogenicity in humans, in which chronic
exposure to high levels of the chemical was found to be associated with an increase in overall
cancer mortality. The data from those studies did not link TCDD exposure directly to the
development of any specific type of cancer. Typical exposure to TCDD appears to be less of a
carcinogenic risk than similar exposure to asbestos, radon, or cigarette smoke. Among humans,
short-term exposure to high levels of TCDD can cause chloracne, a serious skin rash.
Dioxins and their effects on human health
The most consistent toxic effects of dioxin-type chemicals are hyperlipidemia, body weight
loss (particularly body fat loss), anorexia, changes in carbohydrate metabolism, and lipid
peroxidation. The biochemical systems particularly affected are lipoprotein lipases, low-
density-lipoprotein receptors, glucose transporter proteins (GLUTs), vitamin C uptake, and
insulin secretion. Some of these biochemical changes occur at very low doses, and some effects
can last for long time periods. To provide a mechanistic explanation for such actions of dioxins,
available experimental evidence has been reviewed. The most recent discovery indicates that
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) directly acts with isolated cytosolic aryl-
hydrocarbon (Ah) receptor under cell-free conditions even without the presence of the nucleus
and is capable of activating key protein kinases that are involved in the growth factor signal-
transduction pathway. The resulting activation of primary-response transcription factors in the
nucleus appears to play a key role in coordinating vital cell program shifts, including lipid
metabolism.
Health effects: toxic or hazardous. Chemicals can be toxic because they can harm us when they
enter or contact the body. Exposure to a toxic substance such as gasoline can affect your health.

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Since drinking gasoline can cause burns, vomiting, diarrhea and, in very large amounts,
drowsiness or death, it is toxic.
Effects of dioxins on human health
Short-term exposure of humans to high levels of dioxins may result in skin lesions, such as
chloracne and patchy darkening of the skin, 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. TCDD was evaluated by the WHO’s International Agency for Research
on Cancer (IARC) in 1997 and 2012. Based on animal data and on human epidemiology data,
TCDD was classified by IARC as a "known human carcinogen”. However, 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 so-called body burden. Current normal background
exposure is not expected to affect human health on average. However, due to the high toxic
potential of this class of compounds, efforts need to be undertaken to reduce current
background exposure.
Sensitive groups
The developing fetus is most sensitive to dioxin exposure. Newborn, with rapidly developing
organ systems, may also be more vulnerable to certain effects. Some people or groups of people
may be exposed to higher levels of dioxins because of their diet (such as high consumers of
fish in certain parts of the world) or their occupation (such as workers in the pulp and paper
industry, in incineration plants, and at hazardous waste sites).
Prevention and control of dioxin exposure
Proper incineration of contaminated material is the best available method of preventing and
controlling exposure to dioxins. It can also destroy PCB-based waste oils. The incineration
process requires high temperatures, over 850°C. For the destruction of large amounts of
contaminated material, even higher temperatures - 1000°C or more - are required.

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Prevention or reduction of human exposure is best done via source-directed measures, i.e. strict
control of industrial processes to reduce formation of dioxins as much as possible. This is the
responsibility of national governments. The Codex Alimentarius Commission adopted a Code
of Practice for Source Directed Measures to Reduce Contamination of Foods with Chemicals
(CAC/RCP 49-2001) in 2001. Later in 2006 a Code of Practice for the Prevention and
Reduction of Dioxin and Dioxin-like PCB Contamination in Food and Feeds (CAC/RCP 62-
2006) was adopted.
More than 90% of human exposure to dioxins is through the food supply, mainly meat and
dairy products, fish and shellfish. Therefore, protecting the food supply is critical. In addition
to source-directed measures to reduce dioxin emissions, secondary contamination of the food
supply needs to be avoided throughout the food chain. Good controls and practices during
primary production, processing, distribution and sale are all essential in the production of safe
food.
As indicated through the examples listed above, contaminated animal feed is often the root-
cause of food contamination.
Food and feed contamination monitoring systems must be in place to ensure that tolerance
levels are not exceeded. It is the responsibility of feed and food producers to assure safe raw
materials and safe processes during production, and it is the role of national governments to
monitor the safety of food supply and to take action to protect public health. When
contamination is suspected, countries should have contingency plans to identify, detain and
dispose of contaminated feed and food. The affected population should be examined in terms
of exposure (for example, measuring the contaminants in blood or human milk) and effects (for
example, clinical surveillance to detect signs of ill health).
Consumers do to reduce their risk of exposure
Trimming fat from meat and consuming low fat dairy products may decrease the exposure to
dioxin compounds. Also, a balanced diet (including adequate amounts of fruits, vegetables and
cereals) will help to avoid excessive exposure from a single source. This is a long-term strategy
to reduce body burdens and is probably most relevant for girls and young women to reduce
exposure of the developing fetus and when breastfeeding infants later on in life. However, the
possibility for consumers to reduce their own exposure is somewhat limited.

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Identify and measure dioxins in the environment and food
The quantitative chemical analysis of dioxins requires sophisticated methods that are available
only in a limited number of laboratories around the world. The analysis costs are very high and
vary according to the type of sample, but range from over US$ 1000 for the analysis of a single
biological sample to several thousand US dollars for the comprehensive assessment of release
from a waste incinerator.
Increasingly, biological (cell- or antibody) -based screening methods are being developed, and
theuse of such methods for food and feed samples is increasingly being validated. Such
screening methods allow more analyses at a lower cost, and in case of a positive screening test,
confirmation of results must be carried out by more complex chemical analysis.
WHO activities related to dioxins
WHO published in 2015 for the first time estimates of the global burden of foodborne disease.
Dioxins’ effects on fertility and on thyroid function were considered in this context, and only
considering these 2 endpoints shows that this exposure can contribute significantly to
foodborne disease burden in some parts of the world.
Reducing dioxin exposure is an important public health goal for disease reduction. To provide
guidance on acceptable levels of exposure, WHO has held a series of expert meetings to
determine a tolerable intake of dioxins.
In 2001, the Joint Food and Agriculture Organization of the United Nations (FAO)/WHO
Expert Committee on Food Additives (JECFA) performed an updated comprehensive risk
assessment of PCDDs, PCDFs, and “dioxin-like” PCBs.
In order to assess long- or short-term risks to health due to these substances, total or average
intake should be assessed over months, and the tolerable intake should be assessed over a period
of at least 1 month. The experts established a provisional tolerable monthly intake (PTMI) of
70 picogram/kg per month. This level is the amount of dioxins that can be ingested over lifetime
without detectable health effects.

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WHO, in collaboration with FAO, through the Codex Alimentarius Commission, has
established a ‘Code of Practice for the Prevention and Reduction of Dioxin and Dioxin-like
PCB Contamination in Foods and Feed’. This document gives guidance to national and
regional authorities on preventive measures.
WHO is also responsible for the Global Environment Monitoring System’s Food
Contamination Monitoring and Assessment Programme. Commonly known as GEMS/Food,
the programme provides information on levels and trends of contaminants in food through its
network of participating laboratories in over 50 countries around the world. Dioxins are
included in this monitoring programme.
WHO also conducted periodic studies on levels of dioxins in human milk. These studies
provide an assessment of human exposure to dioxins from all sources. Recent exposure data
indicate that measures introduced to control dioxin release in a number of developed countries
have resulted in a substantial reduction in exposure over the past 2 decades. Data from
developing countries are incomplete and do not allow yet a time-trend analysis.
WHO is continuing these studies in collaboration with the United Nations Environmental
Programme (UNEP), in the context of the ‘Stockholm Convention’, an international agreement
to reduce emissions of certain persistent organic pollutants (POPs), including dioxins. A
number of actions are being considered to reduce the production of dioxins during incineration
and manufacturing processes. WHO and UNEP are undertaking global breast milk surveys,
including in many developing countries, to monitor trends in dioxin contamination across the
globe and the effectiveness of measures implemented under the Stockholm Convention.
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.
WHO has established and regularly re-evaluated 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.
6. Suggests a valid management action to deal with that
toxicants:

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Three major ways for the removal of toxicants from body. The body uses several routes to
eliminate toxicants or their metabolites. The main routes of excretion are via
1. urine,
2. feces,
3. and exhaled air.
10 Steps to Avoid Toxic Chemicals
1. Make Your Own Cleaning Products
It’s easy, fun, and cheap to make non-toxic cleaners from safe and effective ingredients like
vinegar and baking soda. Find recipes here. Or better yet, host a Green Cleaning Party to make
these non-toxic cleaners with friends in your community. Certain chemicals in cleaning
products have been linked to reduced fertility, birth defects, increased risk of breast cancer,
asthma, and hormone disruption.
2. Avoid Fragrance
Shop for cleaners, laundry detergents, and personal care products labeled “fragrance-free”
Warning: “Unscented” does not always mean fragrance-free. Don’t use air fresheners. Click
here for tips to reduce odors around the home naturally. Fragrance can be made up hundreds
of chemicals, which companies are legally allowed to keep secret. Common fragrance
chemicals include phthalates (linked to reproductive and developmental harm) and allergens.
3. Give Your Personal Care Products a Makeover
Read the label to avoid chemicals like parabens, sodium laureth sulfate, and oxybenzone.
Check the Skin. Deep database at www.cosmeticsdatabase.com to find safer products. Use
fewer products, and use them less frequently to reduce exposures. Personal care products
contain a wide variety of chemicals, including some known to be of concern, and many that
lack research to prove safety for women’s health. These products are applied directly to our
skin where they are easily absorbed into our bodies.

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4. Go “BPA-Free
Ditch the canned foods when possible and opt for fresh or frozen fruits and vegetables instead.
Look for products packaged in glass or lined cardboard instead of cans. Don’t take paper
receipts at ATMS, grocery stores, etc. unless you really need them. Bisphenol-A (BPA) is
commonly found in can liners, plastic products and paper receipts. BPA exposure is linked to
a host of hormone-related health impacts such as increased risk of cancer, infertility and
obesity. And unfortunately, studies find BPS — BPA’s replacement chemical — isn’t any safer
than BPA. Learn more.
5. Quit the Quats
Reduce your use of disinfectant products. Avoid antibacterial handsoaps, hand sanitizers and
cleaning products which contain quaternary ammonium compounds (quats). Check the front
label and avoid products which contain ingredients that include “…onium chloride” in their
names, like Benzalkonium chloride. Quats are skin irritants, can irritate your lungs and have been
linked to asthma, fertility issues and reproductive harm. The over use of quats can also lead to the
promotion of antibacterial-resistant bacteria (“super-bugs”).
6. Choose Alternatives to Plastics (where possible)
Use glass jars or ceramic bowls to store food. Never microwave plastic. Wash plastics by hand
– not in the dishwasher. Avoid plastics with recycle symbols #3 (PVC), #6 (polystyrene), and
#7 (other) which have greater potential to leach toxics and are difficult to recycle. Plastic
products can contain toxic additives such as phthalates, heavy metals and other compounds
which leach out over time. Polyvinyl chloride (PVC), known as the poison plastic, is found in
plastic products from toys and cookware to shower curtains.
7. Keep Harmful Chemicals Out of the House
Take of your shoes before entering your house to avoid tracking in oils and chemicals from the
street outside. Use a door mat to catch dirt at the door. Dust with a micro-fiber cloth or wet
cloth and vacuum your house regularly (with a HEPA-filter vacuum if you can). Shoes can
track in toxic chemicals like lawn pesticides, coal tar from a driveway, etc. Dust carries harmful
chemicals that shed off of household furniture, electronics, and other household products.

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8. Turn Down the Heat on Non-Stick Cookware
Keep the stove at or below medium heat when using Teflon or non-stick cookware. Opt for
cast iron or stainless-steel pans for cooking when possible. Teflon releases perfluorooctanoic
acid (PFOA) when heated to 450 degrees. PFOA is linked to developmental harm and cancer.
9. Ditch the Air Fresheners
Eliminate odor – Identify the smell and eliminate or prevent it. Check out our tips for reducing
odors around the home.
Open a window – Ventilating your home with outdoor air has been shown to reduce symptoms
associated with asthma, allergies and infections.
Set out a bouquet of fresh or dried flowers to add a floral scent to your home.
Simmer herbs or spices on the stove. Try seasonal alternatives like pine cones, pine needles, or
cinnamon.
9 THE FACTS:
Air fresheners add unnecessary chemicals to your home including ones that may disrupt your
hormones.
10. Join Women’s Voices for the Earth!
Exercise your power to ensure a healthy future. Sign up to receive action alerts, latest news,
and tips for reducing toxic exposures. Donate to our work to eliminate toxic chemicals that
harm women’s health.