Biodiversity International Journal

Review Article Open Access

Dioxins: source, origin and toxicity assessment

Abstract Volume 2 Issue 4 - 2018

Persistent, bioaccumulative and toxic chemicals (PBTs) are substances that can build
Ashok K Rathoure
up to levels that can be harmful to human and ecological health. These contaminants Eco Chem Sales & Services, Ecosystem Resource Management
may travel long distances in the atmosphere and can move readily from land to air Pvt Ltd, India
and water. The accumulation of such chemicals in organisms from the surrounding
environment through absorption, ingestion and inhalation may cause severe health Correspondence: Ashok K Rathoure, Mayashivraj Sadan,
issues. Dioxin is formed as an unintentional by-product of many industrial processes Gupta Colony, Hardoi-241001 (UP) India, Tel +91-9450501471,
involving chlorine such as waste incineration, chemical and pesticide manufacturing, Email asokumr@gmail.com
treatment of hazardous material and pulp and paper bleaching. The potential for health
risks due to the cancer-promoting, immunomodulating and teratogenic activities of Received: December 08, 2017 | Published: July 06, 2018
dioxins in rodents has raised concerns over their presence in the human food chain.
There is an urgent need of taking attention on sources of emission of dioxin and its
mitigation measures. In this chapter, the sources, its origin and toxicity assessment of
dioxin has been presented along with 3 case studies.

Keywords: dioxin, epa, toxic equivalents, bioaccumulation, immunoglobulin

Introduction PCBs that act like dioxin are measured in relation to TCDD. Dioxin
is formed as an unintentional by-product of many industrial processes
The term dioxin refers to a group of chemical compounds sharing involving chlorine such as waste incineration, chemical and pesticide
certain similar structures and biological characteristics.1 Dioxin manufacturing and pulp and paper bleaching. Dioxin is formed by
is the common name for 2,3,7,8-tetrachlorodibenzo-para-dioxin burning chlorine-based chemical compounds with hydrocarbons. The
(TCDD) but is also used for the structurally and chemically related major source of dioxin in the environment comes from waste-burning
polychlorinated dibenzo-para-dioxins (PCDD), dibenzofurans incinerators of various sorts and also from backyard burn-barrels.
(PCDF) and the coplanar polychlorinated biphenyls (PCB). There are Dioxin pollution is also affiliated with paper mills which use chlorine
75 PCDD congeners, 135 PCDF and 209 PCB. Seven PCDD and 10 bleaching in their process and with the production of Polyvinyl
PCDF with substitutions at the 2,3,7 and 8 positions are considered Chloride (PVC) plastics and with the production of certain chlorinated
toxic and 11 PCB have dioxin-like toxicity. Dioxin compounds are chemicals like many pesticides. The major sources of dioxin are in
not created intentionally, but are formed inadvertently by a number of our diet. Since dioxin is fat-soluble, it bioaccumulates, climbing up
human and natural activities. These activities include combustion and the food chain. A North American eating a typical North American
incineration, forest fires, chlorine bleaching of pulp and paper, certain diet will receive 93% of their dioxin exposure from meat and dairy
types of chemical manufacturing and processing and other industrial products (23% is from milk and dairy alone; the other large sources of
processes.2 Many forms of dioxin exist. One form, 2,3,7,8-tetra- exposure are beef, fish, pork, poultry and eggs). In fish, these toxins
chlorodibenzo-p-dioxin (2,3,7,8-TCDD) is considered the most toxic bioaccumulate up the food chain so that dioxin levels in fish are
form. It is also the most studied form. Toxic equivalents (TEQs) are 100,000 times that of the surrounding environment. Dioxin is released
used to describe the toxicity of 16 other forms relative to 2,3,7,8- by paper mills, by metal smelters, by many chemical plants, by many
TCDD. Persistent, bioaccumulative and toxic chemicals (PBTs) are pesticide factories and by all incinerators.
substances that can build up to levels that can be harmful to human
and ecological health. These contaminants may travel long distances Dioxin formation in cement kilns
in the atmosphere and can move readily from land to air and water.
The long residence time and high temperature in the cement kiln as
Bioaccumulation is the accumulation of chemicals in organisms
compared with municipal waste incinerators lead to very low amount
from the surrounding environment through absorption, ingestion and
of PCDD/Fs. In fact, PCDD/Fs and other components of hazardous
inhalation.3 Dioxins dissolve more easily or are more attracted to
waste may actually be destroyed properly in cement kilns if added
oily or fatty compounds than water. Because of this, they are more
directly to the burner.4 Majority of the research done on formation
prevalent in animals with body fat, soils and sediments than they are
of dioxins in cement kilns suggest that these compounds mainly are
in water. The same goes for other wildlife. Dioxin works its way to
formed at the cooler parts of the processes, including the preheater
the top of the food chain. Dioxin was the primary toxic component
region (red colour zone) and post preheater region (blue colour
of Agent Orange, was found at Love Canal in Niagara Falls, NY and
zone). The destruction of hazardous waste in cement kilns, including
was the basis for evacuations at Times Beach, MO and Seveso, Italy
chlorinated hydrocarbons have been analyzed by many researchers
(Table 1). and found more than 99.99% destruction efficiency.5,6 Due to high
Source and origin of dioxins temperature in cement kilns, all the organics are destroyed, therefore
formation of dioxins in cement kilns may be attributed to the preheater
The majority of toxic dioxin is and has been derived from industrial zone and post preheater zone. In the preheater region (red), raw
chlorination processes, incineration of municipal waste and production meal is added, heated with the hot gas coming from rotary kiln and
of certain herbicides. The toxicity of other dioxins and chemicals like calcination occurs in this region. The temperature in this region varies

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from approximately 250-850°C with lower part of pre heater zone at In modern preheater kilns, the emission is lower because of lower
higher temperature and upper part at lower temperature. The raw meal temperature of APCD. The raw gases from the rotary kilns go through
may constitute many particle surfaces, which may facilitate the surface the preheater then through raw mill dryer to heat the raw meal, enter
catalyzed formation of PCDD/Fs.7 At the same time, the lower part of into APCD and then stack gas. This operational mode decreases the hot
preheater zone may facilitate the homogeneous gas phase formation gas temperature and increase the possibility for adsorption of PCDD/
and upper part may participate in heterogeneous formation of dioxins. Fs in APCD. Due to lower temperature and adsorption of PCDD/Fs,
The organic material present in the raw meal, volatilize in the preheater low level of dioxins detected in stack gas. On the other hand, some
zone and become available in the gas stream. Usually there is enough studies show that there are more chances for the formation of dioxins
chlorine present in the raw meal to maintain the formation reactions in APCD, due to adsorption of carbon structures and temperature
of the chlorinated organic compounds (chlorophenols, chlorobenzene profile almost 250-350°C.9
etc.) needed for PCDD/Fs formations.8 The raw gas (kiln gas), may
Karstensen et al.,6 identified the following main sources for the
contain carbon residues and deposited on surfaces of the walls of air
dioxins emissions in cement kilns:
pollution control devices (APCD) blue colour region. The temperature
and oxygen concentration may also be responsible for the formation i. Raw meal, containing naturally occurring PCDD/Fs
of dioxins in APCD. APCD such as electrostatic precipitator (ESP) is
used in cement industries to remove the particulate matter from the ii. PCDD/Fs formed in the preheater zone
flue gas. This particulate matter may adsorb some dioxins on their iii. PCDD/Fs associated with cement kiln dust (CKD), originating
surfaces. from the ESP.
Table 1 Nomenclature for dioxin-like compounds Cement kiln dust (CKD) containing adsorbed dioxins collected
and reintroduced into the process along with raw meal. Karstensen
Term/ et al.,6 proposed that there is region between ESP and preheater
Definition
Symbol
region where PCDD/Fs produced and are present in gaseous as well
Any one particular member of the same chemical family, as adsorbed form. Once dioxins are produced, they will circulate
Congener e.g. there are 75 congeners of chlorinated dibenzo-p- between gaseous and particle adsorbed form.10 Hence, in cement
dioxins. industry dioxins formation could be attributed to the already dioxins
present in the raw meal and the combination of homogeneous and
Group of structurally related chemicals that have the heterogeneous mechanism in the preheater and post combustion
same degree of chlorination. For example, there are zone for the formation of PCDD/Fs are significant.11 Homologue
Homologue
eight homologues of CDDs, monochlorinated through
profile or congener pattern of dioxins within each homologue group
octochlorinated.
may be used to identify the major sources and formation pathways,
Substances that belong to the same homologous class. responsible to the dioxins formation in a specific case. Homologue
Isomer For example, there are 22 isomers that constitute the profile provides the information about the relative proportions of
homologues of TCDDs. mono to Oct-chlorinated compounds and simply described as a single
number indicating the average degree of chlorination. The degree of
Denoted by unique chemical notation. For example, chlorination varies between 1 and 8, where 8 indicates the PCDD
Specific
2,4,8,9-tetrachlorodibenzofuran is referred to as 2,4,8,9-
congener or PCDF as OCDD or OCDF. Some studies show that homologue
TCDF.
profile differs if there are changes in fuel composition and combustion
D Symbol for homologous class: dibenzo-p-dioxin conditions.
F Symbol for homologous class: dibenzofuran Dioxin and health
M Symbol for mono, i.e. one halogen substitution The potential for health risks due to the cancer-promoting,
D Symbol for di, i.e. two halogen substitution immunomodulating and teratogenic activities of dioxins in rodents
has raised concerns over their presence in the human food chain. The
Tr Symbol for tri, i.e. three halogen substitution lipophilic nature of dioxins results in higher concentrations in the fat
T Symbol for tetra, i.e. four halogen substitution of animal and fish products and their excretion via milk secretion in
dairy cattle may result in relatively high concentrations of dioxin
Pe Symbol for penta, i.e. five halogen substitution contamination in high-fat dairy products. Surface contamination of
Hx Symbol for hexa, i.e. six halogen substitution plant foods and soil due to deposition of atmospheric emissions may
also be a significant direct source of dioxin ingestion for livestock and
Hp Symbol for hepta, i.e. seven halogen substitution thereby an indirect source of dioxin for humans. Despite numerous
O Symbol for octa, i.e. eight halogen substitution epidemiological studies, dioxin has not been conclusively determined
to be problematic for humans. Certain management practices such
Chlorinated dibenzo-p-dioxins, halogens substituted in
CDD as trimming fat from meat, consuming low-fat dairy products and
any position
simply cooking food can substantially decrease exposure to dioxin
CDF
Chlorinated dibenzofurans, halogens substituted in any compounds. The EPA report confirmed that dioxin is a cancer hazard
position to people. In 1997, the International Agency for Research on Cancer
PCB Polychlorinated biphenyls (IARC), part of the World Health Organization, published their
research into dioxins and furans and announced on February 14,
Source: EPA, 1989 1997, that the most potent dioxin, 2,3,7,8-TCDD, is a now considered

Citation: Rathoure AK. Dioxins: source, origin and toxicity assessment. Biodiversity Int J. 2018;2(4):310‒314. DOI: 10.15406/bij.2018.02.00079
 Copyright:
Dioxins: source, origin and toxicity assessment ©2018 Rathoure 312

a Group 1 carcinogen, meaning that it’s a known human carcinogen. workers. Other sex hormone levels in these men were affected as
In addition to cancer, exposure to dioxin can also cause severe well. The body burdens that seem to produce an increase in diabetes
reproductive and developmental problems at levels 100 times lower range from 99 to 140ng/kg. Thus the average American, with a body
than those associated with its cancer causing effects. Dioxin is well- burden of 13ng/kg, is a factor of 8 below the lowest level thought
known for its ability to damage the immune system and interfere with to create a diabetes hazard. Dioxin is an astonishingly versatile and
hormonal systems. Dioxin exposure has been linked to birth defects, potent poison.
inability to maintain pregnancy, decreased fertility, reduced sperm
EPA12 characterizes 2,3,7,8-TCDD as a human carcinogen based on
counts, endometriosis, diabetes, learning disabilities, immune system
the weight of evidence of animal and human studies and characterizes
suppression, lung problems, skin disorders, lowered testosterone
other dioxin like compounds i.e. other dioxin-like chlorinated dibenzo-
levels and much more.
p-dioxins [CDDs] and chlorinated dibenzofurans [CDFs] and dioxin-
A very large proportion of dioxin comes from human sources. like polychlorinated biphenyls [PCBs]; as likely human carcinogens.
Dioxin began accumulating in the environment around 1900 when The US Department of Health and Human Services determined that
the founder of Dow Chemical (Midland, Michigan) invented a way it is reasonable to expect that 2,3,7,8-TCDD may cause cancer.13 The
to split table salt into sodium atoms and chlorine atoms, thus making International Agency for Research on Cancer determined that 2,3,7,8-
large quantities of free chlorine available for the first time. The dioxin TCDD is a known human carcinogen.14 Possible human health effects
is toxic to humans in surprisingly many ways and that the general associated with endocrine disruption may include breast cancer and
public is not adequately protected from ill effects by a traditional endometriosis in women, testicular and prostate cancers in men,
margin of safety. Chloracne was the first disease associated with abnormal sexual development, reduced male fertility, alteration
exposure to dioxin, first described in 1897. Chloracne appeared as in pituitary and thyroid gland functions, immune suppression and
an occupational problem in the 1930s among pesticide workers and neurobehavioral effects.15 Although birth defects have been observed
among workers who manufactured industrial chemicals called PCBs in animals (developing animals are especially sensitive) exposed to
(polychlorinated biphenyls). However, dioxin was not identified as higher than background levels of 2,3,7,8-TCDD, human birth defects
the cause of chloracne until about 1960. (Dioxin was an unwanted resulting from exposure to dioxins currently cannot be confirmed.13
contaminant of the pesticides and PCBs.) Chloracne produces skin
eruptions, cysts and pustules like a very bad case of teenage acne; Dioxin toxicity assessment
except that the sores can occur all over the body and in serious cases The study was undertaken by Latchoumycandane & Mathur16 to
can last for many years. investigate whether treatment with vitamin E protects rat testis from
Male body has no ways to get rid of dioxin other than letting it oxidative stress induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin
break down according to its chemical half-lives. Female, on the other (TCDD). Male rats of Wistar strain were administered TCDD at
hand, have two ways which it can exit their bodies: doses of 1, 10 and 100ng per kg body wt. per day for 45 days. Other
groups of animals were co-administered TCDD (1, 10 and 100ng per
a. It crosses the placenta into the growing infant; kg body wt. per day) and vitamin E (20mg per kg body wt. per day)
for 45 days. Animals administered TCDD and those co-administered
b. It is present in the fatty breast milk, which is also a route of
TCDD and vitamin E did not show any significant change in body
exposure which doses the infant, making breast-feeding for non-
weight. Administration of TCDD decreased the weights of the testis,
vegan/vegetarian mothers quite hazardous (Figure 1).
epididymis, seminal vesicles and ventral prostate. The daily sperm
production decreased in the animals administered TCDD from the
control values of 22.19+/-2.67 to 13.10+/-3.16 x 106. There was a
significant decline in the activities of superoxide dismutase, catalase,
glutathionereductase and glutathione peroxidase with concomitant
increased levels of hydrogen peroxide and lipid peroxidation. Co-
administration of TCDD and vitamin E did not show any significant
changes in the weights of the testis, epididymis, seminal vesicles and
ventral prostate. The daily sperm production remained unchanged in
the animals co-administered TCDD and vitamin E. The activities of
antioxidant enzymes and the levels of hydrogen peroxide and lipid
peroxidation did not change in the animals co-administered TCDD
and vitamin E. These results suggested that administration of TCDD
induces oxidative stress in testis and vitamin E could impart a
protective effect against TCDD-induced oxidative stress.17
Figure 1 Dioxin Reassessment by EPA.
The toxicity of TCDDis mediated by activation of the aryl
A TEQ is a dioxin Toxic Equivalent, calculated by looking at all hydrocarbon receptor (AhR), an orphan receptor belonging to the
toxic dioxins and furans and measuring them in terms of the most basic helix-loop-helix Per-ARNT-Sim family of transcription factors.
toxic form of dioxin, 2,3,7,8-TCDD. This means that some dioxins/ TCDD and related chemicals bind to the AhR with high affinity,
furans might only count as half a TEQ if it’s half as toxic as 2,3,7,8- leading to its translocation into the nucleus and dimerization with the
TCDD. Researchers at the National Institute of Occupational Safety AhR nuclear translocator (ARNT). This heterodimeric complex then
and Health (NIOSH) found reduced levels of testosterone (male binds dioxin response elements in the promoters of target genes and
sex hormone) circulating in the blood of dioxin-exposed male regulates their transcriptional expression.18 Mice in which the AhR

Citation: Rathoure AK. Dioxins: source, origin and toxicity assessment. Biodiversity Int J. 2018;2(4):310‒314. DOI: 10.15406/bij.2018.02.00079
 Copyright:
Dioxins: source, origin and toxicity assessment ©2018 Rathoure 313

has been genetically deleted fail to exhibit any overt toxic responses by which the concerns of local affected persons and others who have
typically observed after TCDD exposure,19‒24 demonstrating that AhR plausible stake in the environmental impacts of the project or activity
activation is required to mediate TCDD toxicity. are ascertained with a view to taking into account all the material
concerns in the project or activity design as appropriate. When the
Case studies on dioxin EIA/EMP reaches to public for incineration facility in Sachin GIDC,
the NGO and villagers start opposing the same. They have protested
Case-1: Land fill site at Sachin, Surat (Gujarat) against the proponent and submitted written application to Collector
Hazardous wastes may be detrimental to both human health and other respective authorities against the project development due
and day to day human life. Components of hazardous waste can be to dioxin. On the day, when public hearing was to be conducted,
carcinogenic, teratogenic, corrosive, flammable, explosive and/or villages came with Lathi and made trouble to organizers; this made
releasing toxic fumes. The industries/government need technically the Public consultation postponed by the collector till further action.
feasible and sustainable solutions for the management of hazardous The project is not started till 2018.
waste generated. Gujarat Enviro Protection and Infrastructure Limited
have set up Integrated Common Hazardous Waste Management
Case-3:TSDF at Lothal (Gujarat)
Facility for the treatment, storage and disposal of Hazardous Wastes Industrial Waste Management Services (IWMS) has proposed a
generated by the cluster of Industries in the Surat region. GEPIL has Common Integrated Landfill and Incineration Facility over an area
been established in 1999. of 2,26,089m2 at Saragvala village in Dholka region of Gujarat for
treatment and disposal of Industrial hazardous waste generated from
The dioxins are released during the treatment of hazardous
various industries located in and around the Dist. Ahmedabad and
chemicals. In purview of that, some NGOs had discussion with
Central Gujarat. The project site lies at 22°30’17.05” N Latitude
proponent about the release of toxic gases from the unit and proponent
and 72°16’31.08” E Longitude. The capital investment was Rs.
assured for taking care of any gaseous release. On 17th Jan. 2012,
146.450Crores for landfill (2 Nos. having 15,00,000tons capacity) and
thousands of people from over 30 villages of Surat district took out a
incinerator (5tons/hr. of liquid/solid waste incineration) facility near
rally in Sach in demanding closure of Gujarat Environment Protection
Lothal Archaeological Museum at a distance of 3km in North –West.
Infrastructure Limited (GEPIL). The villagers were protesting
For this set up, the environmental clearance is statuary requirement
ineffective functioning of the company which has been assigned the
and EIA was completed by NABET accredited consultant. As per
critical task of incinerating and treating several tons of hazardous waste
provision for EIA Notification 2006, the Public Consultation is
received from industries in Ankleshwar and Vapi. It has been alleged
required to conduct at site by State Pollution Control Board, hence the
that the company’s incinerator has never functioned properly and the
draft EIA was submitted to SPCB in November 2016 for the same as
toxic waste was disposed into the sea through the Unnkhadi totally
per norms. When the EIA/EMP reaches to public for such set up in the
untreated. The court of chief judicial magistrate, Surat, has issued
area near Lothal Archaeological Museum, some NGO and villagers
summons to the managing director and eight directors of Gujarat
start opposing the landfill and incineration set up. They have protested
Enviro Protection and Infrastructure Limited (GEPIL) based on a
against the proponent and submitted written application to Collector
complaint filed against them for allegedly illegally discharging toxic
and other respective authorities against the project development due
wastes. The officials have been asked to appear before the court on
to dioxin. Before the date of Public consultation, the collector has
March 23, 2012. The complaint was filed by Gujarat Pollution Control
postponed the same till further information. The project is not started
Board (GPCB) regional officer (Surat) Mr. A.G. Patel. According to
till 2018.
the complaint, GEPIL used to discharge untreated factory wastes
directly into the main line of the Common Effluent Treatment Plant
Conclusion
(CETP) at Sachin GIDC, which discharges polluted water into the
Unn creek. Earlier, GPCB had slapped a temporary closure notice on Dioxins are a group of chemically-related compounds that are
the company after people from 32 affected villages took out a rally persistent environmental pollutants. Due to the omnipresence of
against GEPIL.25 dioxins, all people have background exposure, which is not expected
to affect human health. However, due to the highly toxic potential,
Case-2:TSDF proposal at Sachin, Surat (Gujarat) efforts need to be undertaken to reduce current background exposure.
M/s. Thakorji Enviro Techno Pvt. Ltd. has proposed a Common Although formation of dioxins is local, environmental distribution is
Incineration Facility with waste heat recovery boiler over an area global. Dioxins are found throughout the world in the environment.
of 5600m2 at GIDC Sachin, Dist. Surat, Gujarat for treatment and The highest levels of these compounds are found in some soils,
disposal of chemical waste (solid and aqueous) generated from various sediments and food, especially dairy products, meat, fish and shellfish.
industries located in and around the area. The capital investment was Very low levels are found in plants, water and air. Short-term exposure
Rs. 34.25Crores for Incineration (2tons/hr), Waste Heat Recovery of humans to high levels of dioxins may result in skin lesions, such
Boiler (8tons/hr) and waste blending facility for co-processing as chloracne and patchy darkening of the skin, and altered liver
(500tons/month) facility near Sonari Village at a distance of 1.9km function. Long-term exposure is linked to impairment of the immune
in North direction. For this set up, the environmental clearance is system, the developing nervous system, the endocrine system and
statuary requirement and EIA was completed by NABET accredited reproductive functions. Proper incineration of contaminated material
consultant. As per provision for EIA Notification 2006, the Public is the best available method of preventing and controlling exposure
Consultation is required to conduct at site by State Pollution Control to dioxins. It can also destroy PCB-based waste oils. The incineration
Board, hence the draft EIA was submitted to SPCB in March 2014 process requires high temperatures, over 850°C. For the destruction
for the same as per norms. Public Consultation refers to the process of large amounts of contaminated material, even higher temperatures
like 1000°C or more are required. There is an urgent need to take care

Citation: Rathoure AK. Dioxins: source, origin and toxicity assessment. Biodiversity Int J. 2018;2(4):310‒314. DOI: 10.15406/bij.2018.02.00079
 Copyright:
Dioxins: source, origin and toxicity assessment ©2018 Rathoure 314

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Conflict of interest
15. EPA. Special Report on Environmental Endocrine Disruption: An
Author declares that he has no conflict of interest. Effects Assessment and Analysis. US Environmental Protection Agency.
Washington, DC; 1997. 111 p.
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Citation: Rathoure AK. Dioxins: source, origin and toxicity assessment. Biodiversity Int J. 2018;2(4):310‒314. DOI: 10.15406/bij.2018.02.00079