Study on the adverse effect of tannery effluent on hazaribagh tanning area and pollution management

Study on the Adverse Effect of Tannery Effluent on
Hazaribagh Tanning Area and Pollution Management.
A dissertation for the partial fulfillment of the requirements for the
degree of M. Sc in Environmental Science.
SUBMITTED TO
Department of Environmental Science
State University of Bangladesh (SUB)
SUBMITTED BY
Ahmed Istiaq Murad
ID No. : PG 05-32-14-005.
August, 2015

DEDICATED
TO
MY RESPECTED AND BELOVED
PARENTS AND TEACHER

i
CERTIFICATION
This is to certify that this thesis paper titled “Study on the Adverse Effect of Tannery
Effluent on Hazaribagh Tanning Area and Pollution Management‖ is carried out under
direct supervision of myself for the requirement of partial fulfillment for the degree of
Masters of Environmental Science at State University of Bangladesh (SUB). In my capacity
as supervisor of the candidate‘s thesis, I certify that the above statements are true to the best
of my knowledge.
…………………………
(Kazi Farhad Iqbal)
Assistant Professor
Department of Environmental Science
State University of Bangladesh (SUB)
&
Respected Supervisor

ii
DECLARATION
I do hereby declare that this thesis paper titled “Study on the Adverse Effect of Tannery
Effluent on Hazaribagh Tanning Area and Pollution Management” is a presentation of
my original research work. Wherever contributions of others are involved, every effort is
made to indicate this clearly, with due reference to the literature, and acknowledgement of
collaborative research and discussions. This Thesis paper submitted as the partial fulfillment
for the degree of Masters of Environmental Science under direct supervision of Assistant
Professor (Kazi Farhad Iqbal), at State University of Bangladesh (SUB). The present study
work is original and has not been submitted for publishing in partially or for fully or any
other degree also.
…………………………..
(Ahmed Istiaq Murad)
ID No. : PG 05-32-14-005
August, 2015

iii
ACKNOWLEDGEMENT
At the beginning, I am expressing my sincere gratefulness to the Almighty Allah for
enabling me to prepare this Thesis paper in a complete form within a short period
successfully.
Special mention should go to my honorable Kazi Farhad Iqbal, Assistant Professor,
Department of Environmental Science, State University of Bangladesh (SUB) for his
constant, and constructive guidance throughout the study. Without his help it would have
been so difficult to prepare this report.
I am also grateful to the help and guidance of all members of Department of Environmental
Science, State University of Bangladesh (SUB). I am to all of my course teachers for giving
me valuable advice.
I am also expressing my gratitude to Mr. Nur-E-Alam, Senior Scientific Officer, Leather
Research Institute (LRI), Bangladesh Council for Scientific and Industrial Research (BCSIR)
for giving me a huge support for preparing this thesis paper.
Finally, I would show my humble gratitude to all of the individuals who have helped me to
prepare this report within very short period of time. As being a human being, it is natural to
forget few names may not be mention forgetfully. I would like to apologies forgetfulness.
With the best regards
Ahmed Istiaq Murad
August, 2015

iv
Table of Contents
ABSTRACT...............................................................................................................................1
CHAPTER 01: INTRODUCTION............................................................................................2
1.1 Environmental Science.....................................................................................................2
1.2 Environmental management.............................................................................................2
1.3 Water pollution.................................................................................................................3
1.4 Surface water...................................................................................................................3
1.5 Classification of non-saline surface water quality ...........................................................4
1.6 Sources of Water Pollution ..............................................................................................4
1.7 Causes of Water pollution................................................................................................5
1.8 Surface water in Bangladesh............................................................................................7
1.9 Aim of the Thesis...........................................................................................................11
1.10 Methodology ................................................................................................................11
CHAPTER 02: LITERATURE REVIEW...............................................................................12
CHAPTER 03: LEATHER TANNING AND ENVIRONMENTAL POLLUTION..............15
3.1 Some Definitions:..........................................................................................................15
3.2 Composition of hides and skins. ...................................................................................16
3.3 Different Layers of raw hide / skin ...............................................................................17
3.4 Anatomy of Hide / Skin .................................................................................................18
3.5 Mechanism of putrefaction of raw hides and skins.......................................................20
3.6 Division of a Hide ..........................................................................................................22
3.7 Leather Tanning .............................................................................................................24
3.8 The Tanning Process ......................................................................................................25
Preparation of the Raw Pelt for Tanning..........................................................................26
Pretanning, Tanning and Retanning .................................................................................27
Mechanical Operations.....................................................................................................27
Retanning..........................................................................................................................28
Dyeing, Fatliquoring and Drying......................................................................................28
Finishing...........................................................................................................................29
3.9 Waste produced during Tanning processes...................................................................30
Wet Blue Stages................................................................................................................30
Crusting ............................................................................................................................33

v
3.10 The polluting features of the tannery waste on different surfaces ...............................36
3.11 Chemicals used in Tanning process .............................................................................38
1. High potential Hazard group ........................................................................................38
2. Moderate potential hazard groups ...............................................................................39
3 . Low potential Hazard group.......................................................................................39
3.12 Effect of Chemicals on Human Body .........................................................................39
3.13 Environmental Impact of of the main constituents of Tannery Wastes ......................55
Solids ................................................................................................................................55
Oxygen demand................................................................................................................56
Nitrogen............................................................................................................................58
Sulphides (S2-
) ..................................................................................................................59
Neutral salts ......................................................................................................................59
Chlorides (Cl-
) ..................................................................................................................60
Oils and grease..................................................................................................................61
pH value............................................................................................................................61
Chromium compounds .....................................................................................................62
CHAPTER 04: EXPERIMENTAL..........................................................................................64
4.1 pH...................................................................................................................................64
4.2 Dissolved Oxygen (DO).................................................................................................65
4.3 Biochemical Oxygen Demand (BOD) ...........................................................................66
4.4 Chemical Oxygen Demand (COD) ...............................................................................67
4.5 Chromium (Cr)...............................................................................................................68
4.6 Chloride ( Cl-
).................................................................................................................71
4.7 Total Solids, Dissolved Solids and Suspended Solids ...................................................72
4.8 Sulphide..........................................................................................................................73
CHAPTER 05: DATA ANALYSIS ........................................................................................74
5.1 Study Area: Hazaribagh Tanneries ................................................................................74
5.2 The Toxic Chemicals used in the Tanneries of Hazaribagh...........................................75
Tanneries Discharge 21,600 Liters of Liquid Wastes Daily ............................................77
5.3 River Pollution ...............................................................................................................77
Health Hazards .................................................................................................................78
5.4 Sampling........................................................................................................................80
Result and Discussion:......................................................................................................82
5.5 Overall Buriganga Situation...........................................................................................85
Results and discussion......................................................................................................87

vi
CHAPTER 06: MITIGATION MEASURES OF ENVIRONMENTAL IMPACT OF
TANNERY EFFLUENT .............................................................................................90
6.1 Reducing the environmental impact of the unhairing-deliming process in the leather
tanning industry....................................................................................................................90
Materials and methods......................................................................................................91
6.2 Modifying the Chrome Tanning Process .......................................................................92
1. Masking in chrome tanning..........................................................................................93
2. Increasing collagen reactivity.......................................................................................93
6.4 Post Tanning...................................................................................................................96
1. Post tanning with chrome retanning.............................................................................96
2. Post tanning with chrome retanning and chrome precipitation ...................................98
3. Post tanning without chrome retanning.......................................................................98
4. Chromium recovery and reuse......................................................................................99
5. Process Modification ..................................................................................................100
6.5 Emission Guidelines.....................................................................................................101
6.6 Cleaner technologies ....................................................................................................102
Pollution load..................................................................................................................103
6.7 Treatment of Tannery Effluent.....................................................................................105
6.8 Basic plant monitoring and control..............................................................................109
6.9 Combustion of tannery waste as a comprehensive method of its utilization ...............111
6.10 Preparation of Eco-Friendly Leather by Process Modifications to Make Pollution Free
Tanneries ............................................................................................................................112
1. Silicate Tanning Method ............................................................................................112
2. Carbon dioxide tanning ..............................................................................................114
6.11 Routine Survey...........................................................................................................115
6.12 Mitigation Measures..................................................................................................118
CHAPTER 07: CONCLUSION ............................................................................................120
Works Cited ...........................................................................................................................122

vii
List of figures
Figure 1:Point source water pollution........................................................................................5
Figure 2: Composition of hides and skins (Sharphouse, 1995). ..............................................16
Figure 3: Layers of a hide (Sharphouse, 1995)........................................................................17
Figure 4: Anatomy of hides and skins (Sharphouse, 1995).....................................................18
Figure 5: Parts of hide or skin (Justin, 2013)...........................................................................22
Figure 6: General Flow Diagram for Leather Tanning and Finishing Process........................24
Figure 7: Used dye liquor mixing with the drain water...........................................................34
Figure 8: Leather finishing in the open air...............................................................................35
Figure 9: Buffing dust on the street .........................................................................................36
Figure 10: Tannery waste mixing with drain water.................................................................36
Figure 11: Tannery waste on land………..………………………………………………37
Figure 12: Tannery effluent mixes with sewer. ........................................................37
Figure 13: pH of collected samples .........................................................................................82
Figure 14: BOD of collected samples......................................................................................82
Figure 15: COD of collected samples......................................................................................83
Figure 16: Chromium (Cr) content of collected samples.........................................................83
Figure 17: Chloride (Cl-) contents of collected samples ........................................................84
Figure 18: Factors to be optimised in the chrome tanning process..........................................92
Figure 19: Sources and types of pollutants generated in leather processing .........................104
Figure 20: Layout of in -house segregation of streams, including chrome recycling and
oxidation of sulphides in liming effluent................................................................106
Figure 21: Flowchart of in-house segregation of streams, including chrome recycling,
treatment of liming effluents and pre-treatment of mixed effluent.........................107
Figure 22: Plant monitoring and control parameters .............................................................110

viii
Figure 23: Set up of the high pressure view (M. Renner)......................................................114
Figure 24: left: Cr content of leather and solution using CO2 tanning right: Percentage
approach of good leather quality using CO2 tanning .............................................115
Figure 25: Survey paper for civil learned people...................................................................117

ix
List of Tables
Table 1 : Potential chemical and gaseous contaminants produced at different stages of leather
processing .................................................................................................................38
Table 2: Information about tanneries.......................................................................................74
Table 3: Common pollutants, their sources and associated health effect on human, ..............78
Table 4: Percentage of households suffering from various diseases (Voumik, 2008).............79
Table 5: Comparison of water quality Parameters of Hazaribagh Tanning Area with the
Standard Limit (ECR_97).........................................................................................85
Table 6: Analysis of waste of Hazaribagh tanneries................................................................86
Table 7: Water quality of Buriganga .......................................................................................86
Table 8: Environmental Impact Assessment (EIA) of tanneries (M. R. Azom, 2012)............87
Table 9: Chrome concentration in residual floats from high-exhaustion and conventional
tanning process..........................................................................................................94
Table 10: Efficiency of high-exhaustion chrome tanning process compared to conventional
process based on experience in Western Europe ......................................................95
Table 11: Chrome distribution after post tanning with chrome retanning (related to shaved
weight) ......................................................................................................................97
Table 12: An example of mass balance in leather processing ...............................................103
Table 13: An example of average total pollution load – concentration in combined raw
effluent, conventional process, water consumption: 45 m3/tone............................103
Table 14: An example of pollution load, conventional process.............................................105
Table 15: Preparation of eco friendly leather (M.Sathiyamoorthy, 2013).............................113

Study on the Adverse Effect of Tannery Effluent on Hazaribagh Tanning
Area and Pollution Management P a g e | 1
ABSTRACT
Leather sector is a major industrial sector in Bangladesh and has been playing a significant
role in the country’s economy from the beginning of industrialization. Though having massive
importance, this overgrowing sector has received much criticism on health, environmental as
well as the social context of the country. It is one of the most energy intensive industries in
Bangladesh but absence of proper waste management, using inferior technologies, lack of
facilities for treating industrial wastes; tanning industries located in Hazaribagh, Dhaka are
aggravating environmental problems day by day. In Bangladesh, eco-toxicity evaluation of
any aquatic environment has not been conducted in large scale so far. Tanneries discharge
wastes to the marshy land like rivers and canals which carry toxic chemical like Hydrogen
sulphide, ammonia, poisonous chlorine and nitrogen based gases. The discharging and
dumping of wastes near the water bodies without treatment makes it almost look like an area
which is lying under the blanket of pollution. The worst part is, this bad impact transports to
others through food chain. This study focuses on Surface Water Quality of Hazaribagh
Tanning Area, to assess the present situation arising from such activities and propose several
mitigation measures. We cannot prevent water being polluted cent percent, but minimization
is essential. Several government decisions has been made to revive the tolerant condition of
Hazaribagh Tanning Area including Buriganga among which the Tannery Shifting to Savar
area and subsidies to the toxic industries for establishing Effluent Treatment Plant (ETP) can
be mentioned, but none of these projects have been implemented yet. Sustaining tanning
process through conservation, recovery and better utilization of chromium is necessary to
commence. The present tanneries which use chrome tanning process can be modified by
silicate tanning process or carbon dioxide tanning process to make tanneries pollution free
as well as eco-friendly and the future generations can be protected from dangerous
environmental impacts caused by chromium compounds.

CHAPTER 01
INTRODUCTION
1.1 Environmental Science
Environmental science is the field of science that studies the interactions of the physical,
chemical, and biological components of the environment and also the relationships and effect
of these components with the organisms in the environment. The field of environmental
science can be divided into three main goals, which are to learn how the natural world works,
to understand how we as humans interact with the environment, and also to determine how
we affect the environment. The third goal of determining how humans affect the environment
also includes finding ways to deal with these effects on the environment1
.
1.2 Environmental management
Environmental management is a systematic strategy that companies can use to find
different ways for saving water, energy, and materials, and reducing negative environmental
impacts. Environmental resource management tries to identify factors affected by conflicts
that rise between meeting needs and protecting resources. It is thus linked to environmental
protection and sustainability2
.
1
study.com. Web site (n.d.). What is Environmental Science? -Definition and Scope of the Field. Retrieved on
September 05, 2015 from http://study.com/academy/lesson/what-is-environmental-science-definition-
and-scope-of-the-field.html
2
study.com. Web site (n.d.). Benefits of Effective Environmental Management in Businesses. Retrieved on
September 05, 2015 from http://study.com/academy/lesson/what-is-environmental-science-definition-
and-scope-of-the-field.html

1.3 Water pollution
Water pollution can be defined in many ways. Usually, it means one or more substances
have built up in water to such an extent that they cause problems for animals or people.
Oceans, lakes, rivers, and other inland waters can naturally clean up a certain amount of
pollution by dispersing it harmlessly. If you poured a cup of black ink into a river, the ink
would quickly disappear into the river's much larger volume of clean water. The ink would
still be there in the river, but in such a low concentration that you would not be able to see it.
At such low levels, the chemicals in the ink probably would not present any real problem.
However, if you poured gallons of ink into a river every few seconds through a pipe, the river
would quickly turn black. The chemicals in the ink could very quickly have an effect on the
quality of the water. This, in turn, could affect the health of all the plants, animals, and
humans whose lives depend on the river3
.
1.4 Surface water
Surface water is water on the surface of the planet such as in a stream, river, lake, wetland,
or ocean. It can be contrasted with groundwater and atmospheric water.
Non-saline surface water is replenished by precipitation and by recruitment from ground-
water. It is lost through evaporation, seepage into the ground where it becomes ground-water,
used by plants for transpiration, extracted by mankind for agriculture, living, industry etc. or
discharged to the sea where it becomes saline4
.
3
Woodford, Chris. (2006) Water Pollution. Retrieved on September 06, 2015 from
http://www.explainthatstuff.com/waterpollution.html
4
Wikipedia Web site. (2015) Surface Water. Retrieved on September 06,2015 https://en.wikipedia.org/wiki/Surface_water

1.5 Classification of non-saline surface water quality
The field of hydrometry classifies fresh surface water quality into five categories:
Class 1 is extra-clean fresh surface water resource used for conservation, not necessarily
required to pass through a water treatment process, and requiring only an ordinary process for
pathogenic destruction and ecosystem conservation where basic organisms can breed
naturally.
Class 2 is very clean fresh surface water resource used for consumption, which requires an
ordinary water treatment process before use, for aquatic organism of conservation, fisheries,
and recreation.
Class 3 is medium-clean fresh surface water resource used for consumption, which requires
passing through an ordinary treatment process before use for agriculture.
Class 4 is fairly clean fresh surface water resource used for consumption, but requires a
special water treatment process before use for industry.
Class 5 is the source which is not classified in class 1-4 and only suitable for navigation use5
.
1.6 Sources of Water Pollution
Water pollutant sources can be grouped into two categories:
Point Source -Point source water pollution refers to contaminants that enter a waterway from
a single, identifiable source, such as a pipe or ditch. Examples of sources in this category
include discharges from a sewage treatment plant, a factory, or a city storm drain. The U.S.
Clean Water Act (CWA) defines point source for regulatory enforcement purposes. The
CWA definition of point source was amended in 1987 to include municipal storm sewer
5
Sensagent Web site. (n.d.) Surface Water. Retrieved on September 06, 2015 from
http://dictionary.sensagent.com/Surface%20water/en-en/#Information company

systems, as well as industrial storm water, such as from construction sites. (Water pollution,
2015)
Figure 1:Point source water pollution6
Nonpoint source pollution (NPS) - refers to diffuse contamination that does not originate
from a single discrete source. NPS pollution is often the cumulative effect of small amounts
of contaminants gathered from a large area. A common example is the leaching out of
nitrogen compounds from fertilized agricultural lands. Nutrient runoff in storm water from
"sheet flow" over an agricultural field or a forest are also cited as examples of NPS pollution
(Water pollution, 2015).
1.7 Causes of Water pollution
1. Industrial waste: Industries produce huge amount of waste which contains toxic
chemicals and pollutants which can cause air pollution and damage to us and our
environment. They contain pollutants such as lead, mercury, sulphur, asbestos, nitrates and
6
Allison M. (n.d.) Blendspace. Retrieved on September 06, 2015 from
https://www.blendspace.com/lessons/VTEci9WPntX6PA/point-and-nonpoint

many other harmful chemicals. Many industries do not have proper waste management
system and drain the waste in the fresh water which goes into rivers, canals and later in to sea.
The toxic chemicals have the capability to change the color of water, increase the amount of
minerals, also known as Eutrophication, change the temperature of water and pose serious
hazard to water organisms.
2. Sewage and waste water: The sewage and waste water that is produced by each
household is chemically treated and released in to sea with fresh water. The sewage water
carries harmful bacteria and chemicals that can cause serious health problems. Pathogens are
known as a common water pollutant; the sewers of cities house several pathogens and thereby
diseases. Microorganisms in water are known to be causes of some very deadly diseases and
become the breeding grounds for other creatures that act like carriers. These carriers inflict
these diseases via various forms of contact onto an individual. A very common example of
this process would be Malaria.
3. Mining activities: Mining is the process of crushing the rock and extracting coal and other
minerals from underground. These elements when extracted in the raw form contains harmful
chemicals and can increase the amount of toxic elements when mixed up with water which
may result in health problems. Mining activities emit several metal waste and sulphides from
the rocks and is harmful for the water.
4. Marine dumping: The garbage produce by each household in the form of paper,
aluminum, rubber, glass, plastic, food if collected and deposited into the sea in some
countries. These items take from 2 weeks to 200 years to decompose. When such items enters
the sea, they not only cause water pollution but also harm animals in the sea.
5. Accidental Oil leakage: Oil spill pose a huge concern as large amount of oil enters into
the sea and does not dissolve with water; there by opens problem for local marine

wildlife such as fish, birds and sea otters. For e.g.: a ship carrying large quantity of oil may
spill oil if met with an accident and can cause varying damage to species in the ocean
depending on the quantity of oil spill, size of ocean, toxicity of pollutant.
6. Chemical fertilizers and pesticides: Chemical fertilizers and pesticides are used by
farmers to protect crops from insects and bacterias. They are useful for the plants growth.
However, when these chemicals are mixed up with water produce harmful for plants and
animals. Also, when it rains, the chemicals mixes up with rainwater and flow down into rivers
and canals which pose serious damages for aquatic animals (What is Water Pollution?).
1.8 Surface water in Bangladesh
In Bangladesh rainfall and TRANS-BOUNDARY RIVERS flows are the main sources of surface
water. Bangladesh has an average annual surface flow of about 1,073 million acre feet
(MAF), of which about 870 MAF (93%) are received from India as inflow and rest 203 MAF
(7%) as rainfall. This water is enough to cover the entire country to a depth of 9.14m. About
132 MAF (65% of rainfall and 12% of total) are lost in evaporation (114.30 cm) and the rest
flows to the BAY OF BENGAL.
River water Bangladesh has about 700 rivers including tributaries and distributaries, which
criss-cross the landscape and create about 98,000 ha of inland water bodies and more than
24,000 km streams or water channels. Of these, 54 rivers, including the GANGES and the
BRAHMAPUTRA, originate from India and 3 originate from Myanmar. About 93% catchment
areas of these 58 rivers are beyond Bangladesh, while only 7% is in Bangladesh. During the
dry season when IRRIGATION is necessary, these rivers either flow at their lowest levels or
become dry in the Bangladesh portion, due to upstream BARRAGEs, built in the upper riparian
region.

The river system that flows through Bangladesh comprises the third largest source of fresh
water discharge to the world's oceans. Only the Amazon in Brazil and the Congo in Africa
have larger discharges than the Ganges-Brahmaputra-Meghna river system. The annual
volume of flow past Baruria, just below the confluence of the Brahmaputra and Ganges, is
795,000 million cu m, which is equivalent to 5.52 m of depth over the 14.40 million ha of the
land area of Bangladesh.
The surface water resources available in Bangladesh can be expressed in terms of monthly
stream flow, dry season static water (or standing water) and in-stream storage potential. Total
available stream flow in the country, which is total outflow to the Bay of Bengal, varies from
174,000 comic in August to 5,63 cumec in 1990 water use conditions. Total inflow to
Bangladesh from India is approximately 90% of the total available stream flow in the
country. About 85% of dry season (January-April) stream flow are found in the main river
systems (Ganges-Brahmaputra-Meghna). Streamflow in the individual catchment region,
excluding the stream flow in the main rivers, is extremely limited, with the exception of the
augmented flow in the KARNAFULI River in the southeast region and stream flow in the
Barisal-Patuakhali area in the mid-south region.
Total in-stream storage potential in the country during the dry season is estimated to be about
65 cumec. This estimation is based on a depth of one meter abstraction for the rivers having a
width less than or equal to 100m. The mean monthly available stream outflow in the
northwest region varies from about 417 cumec in March to about 7,970 cumec in August.
Mean monthly inflow from India to the region in the driest month (March) is about 406
million cumec. The major shares of stream flow during March are concentrated in the TISTA
(37%), DUDHKUMAR (30%), DHARLA (19%) and MAHANANDA (19%). Available static water is
about 167 million cu m, and in-stream storage potential is about 103 million cu m.

In the northeastern region, the mean monthly stream flow varies from about l00 cumec in
February to about 18,700 cumec in July. Mean monthly inflow from India to the region in
February is about 223 cumec. In addition, the region receives about 80 cumec from the
Brahmaputra in February. Inflow exceeds outflow in February by about 203 cumec. Major
sources of stream flow during February are the Manu-Kushiyara (75%), SURMA (25%),
DHALESHWARI (17%) and OLD BRAHMAPUTRA (17%). Available static water is about 374
million cu m and interstream potential is estimated to be about 275 million cu m.
The mean monthly available stream flow in the southeast region varies from 377 cumec in
March to 4,870 cumec in July. About 89% of the stream flow during the driest month
(March) is the augmented flow in the Karnafuli from KAPTAI LAKE. Other significant sources
of stream flow for March are the GUMTI (3%), FENI (3%), SANGU (3%) and MATAMUHURI
(2%).
In south-central region the mean monthly stream flow varies from 1,120 cumec in March to
21,500 cumec in August. Over 80% of the available dry season flow enters the region through
the Lower Meghna offtakes - the Abupur, Hizla and Ramdaspur. Major sources during March
are the BISHKHALI (41%), BURISHWAR (28%) and ARIAL KHAN (5%). Available static water is
9 million cu m and in-stream storage potential is 3.9 million cu m.
The mean monthly available stream flow in the south-western region varies from 190 cumec
in March to 7,650 cumec in August - the cross border flow from India through the
Mathabhanga River varies from 1.7 cumec in April to 124 cumec in September. Significant
sources during March is the GORAI (57%) a distributary of the Ganges, the Ganges-Kobadak
intakes (27%) and the Mathabhanga (1.6%). Available static water is 62 million cubic m, and
interstream storage potential is 65 million cu m. Streamflow in about 45% of the region have
salinity greater than 2,000 µ-mohs.

Water in ponds and beels there are about 1.3 million ponds in Bangladesh covering about
1,47,000 ha area. There are about 10,000 HAORs, BAORs and beels. Most of these become
waterless during the winter season. These ponds can be converted to potential mini
RESERVOIRs for irrigation water and/or fish cultivation through planned excavation and
utilization. Total available static water (water contained in the topographical DEPRESSIONs
including haors, baors and beels) in the country during the dry season is about 79 cumec (611
million cu m) under water use condition in 1990. This Figure was based on depths of 0.5, 0.5,
0.0, and 0.5m abstraction for the northwest, northeast, southeast and southwest regions,
respectively, at 24-hour/day continuous pumping for a 90-day period.
Flood water almost every year, FLOODs in Bangladesh cover almost one-third of the land
area, and in years of severe flood, almost half of the country. Large areas of central and
northeastern Bangladesh are normally flooded each year. In general, seasonal flooding is
shallow in the northwest, west and east, but deep in the centre and northeast. Flooding depths
vary within small areas because of differences in topography and man-made modifications of
the land surface.
Although an immense quantity of surface water flows through Bangladesh, the development
potential is constrained for a number of reasons. Most importantly, there are very few
opportunities for either gravity diversions or surface storage. Under existing conditions,
annual outflows from the major rivers to the Bay of Bengal are essentially equal to inflows
from India. A water balance study for the critical dry month of March indicates that even in
this month of relatively high diversions for irrigation and low base flow, the net diversions
from the entire system are only about five percent of the inflows. Under future development
conditions, diversions may possibly increase to 15% without major barrages and up to
perhaps 35% with barrages (Surface Water, 2015).

1.9 Aim of the Thesis:
 To identify the causes and sources of surface water degradation at the study area.
 To provide an actual scenario of impact of tannery waste on Hazaribagh Tanning area
and buriganga River To identify the causes and sources of surface water degradation at
the study area..
 To identify the degree of pollution
 To suggest some mitigation measures to save the surrounding environment from further
degradation.
1.10 Methodology
The study conducted by a series of the following tasks:
 To visit tanneries and surrounding areas.
 To test various water quality parameters to evaluate the surface water quality in
Hazaribagh Tanning area.
 On-site assessments and interviews with relevant personnel including workers, managers
and other stakeholders.
 To find alternative tanning processes instead of Crome tanning method giving almost the
same quality but less harmful for the environment, research carried out on studying
collaborative research papers, articles, journals and discussions.

CHAPTER 02
LITERATURE REVIEW
Tanning Industry is considered as a major source of pollution and tannery wastewater in
particular, is a potential environmental concern. Tanning industry wastes poses serious
environmental impact on water with its high oxygen demand, discoloration and toxic
chemical constituents, terrestrial and atmospheric systems. Tannery waste characteristically
contains a complex mixture of both organic and inorganic pollutants.
The tanning industry causes horrendous environmental pollution and high environmental
impact of tannery effluents makes its treatment an essential fact, mainly due to its volume,
nature and concentration of pollutants such as tanning agents (chromium and tannin), color,
organic matter and others. Many authors have worked regarding tanneries of Hazaribagh
before showing the impact of various pollutants on water, water test results, health hazards
and some measures.
According to Imamul Huq (1998), various chemicals are used during the soaking, tanning and
post tanning processing of hides and skins. The main chemicals used include sodium sulphite
and basic chromium sulphate including non-ionic wetting agents, bactericides, soda ash, CaO,
ammonium sulphide, ammonium chloride and enzymes. Others are sodium bisulphate,
sodium chlorite, NaCl, H2SO4, formic acid, sodium formate, sodium bicarbonate, vegetable
tannins, syntans, resins, polyurethane, dyes, fat emulsions, pigments, binders, waxes, lacquers
and formaldehyde. Various types of processes and finishing solvents and auxiliaries are used,
as well. It has been reported that only about 20% of the large number of chemicals used in the
tanning process is absorbed by leather, the rest is released as waste. Hazaribagh which is the
largest tannery region in Bangladesh consists of more than 200 tanneries generate 7.7 million
liters of liquid waste and 88 million tons of solid waste every day. The direct discharge of

these wastes has contaminated the ground and surface water with dangerously high
concentrations of chromium, as well as cadmium, arsenic, and lead. The contamination of
rivers also allows these pollutants to accumulate in common fish and shellfish species, which
are used as local food sources.
The dumping of untreated liquid tannery wastes from tannery industries at Hazaribagh,
Dhaka is the major source of pollution of Buriganga. The chromium released from the
Hazaribagh tannery industries has been contaminating the water of the river Buriganga for the
last 45 years. A statistics available from the Department of Environment reveal that 95 per
cent of the tannery industries have been built in unplanned way at the congested places of
Hazaribagh during the last fifty years. According to a recent estimate, about 60,000 tons of
raw hides and skins are processed in these tanneries every year, which release nearly 95,000
liters of untreated effluents into the open environment daily, resulting into the dead river
Buriganga.
A project work was studied by Md. Ariful Islam Juel in 2012 on pollution level caused by
effluent of retanning and finishing operation and found that every stage of operation emits
high pollution load.
Chromium is a naturally occurring heavy metal that can exist in air, water, soil, and food, and
common exposure pathways include ingestion, inhalation, and dermal contact. The primary
health impacts from chromium are damage to the gastrointestinal, respiratory, and
immunological systems, as well as reproductive and developmental problems. Chromium is a
known human carcinogen. In addition, the chromium-laced solid wastes from tanneries are
often converted into poultry feed as is the case in areas of Bangladesh—and can thus impact
livestock and humans . According to the WHO, over 8,000 workers in the tanneries of
Hazaribagh suffer from gastrointestinal, dermatological, and other diseases, and 90% of this
population die before the age of 50.

It is an important issue for Bangladesh to face such pollution due to effluent discharged from
tanneries, in such a state, where Hazaribagh Tanning Area is nothing but a blanket of
pollution.
Therefore, it is high time to find out alternatives in sustainable manner to safe Hazaribagh
Tanning Area, Buriganga, as well as Dhaka city. This study is to measure optimum pollution
generated particularly by tannery industries and to seek some mitigation measures to get back
the environmental condition in an acceptable range through sustainable practice.

CHAPTER 03
LEATHER TANNING AND ENVIRONMENTAL POLLUTION
3.1 Some Definitions:
Tan - The word ‗Tan‘ means Oak bark in Latin.
Tanning - It‘s a process of converting putrescible hides and skins to non-putrescible leathers
with definite physical, chemical and biological properties so that they can be used in our daily
life and industries.
Tanning agent / Tannin - A number of materials are used during the tanning process like
natural, synthetic, organic and inorganic etc. These materials are refereed to as Tanning agent
or Tannin. Examples: chromium, mimosa, chestnut, oak, tanoak, hemlock, quebracho,
mangrove, wattle, and myrobalan. The word ‗Tannin‘ was first introduced by Seguim in 1796
to denote the water extractable matter in certain plant tissues capable of converting animal
hide/skin into leather.
Hides - The outer covering of big domestic animals like cow, buffalo, horse, camel, elephant,
whale, etc. are called hides.
Skins - The outer covering of small domestic and / or wild animals like sheep, chamois etc
are called skins. Exception: Tiger is as big as or sometimes bigger than cow but as it is wild,
it is called skin.
We can also differentiate hide and skin on the basis of green weight of them---
< 15 Ib = Calf skin
15 Ib - 25 Ib = Kip skin
25 Tb – 30 Ib = Weight kip
> 30 Ib = Hide

< 53 Ib = Light hide
> 53 Ib = Heavy hide (Dutta, 1973).
Leather - Leather is a valuable by-product of the meat industry. It is the collagen in the
tanned state and it is processed by converting putrescible outer covering of animal to non-
putrescible substance with definite physical, chemical and biological properties so that it can
be used in our daily life and industries. Leather is a product made by stabilizing the proteins
of animal skins through tanning (Dutta, 1973).
3.2 Composition of hides and skins.
Fresh hides / skins consist of protein, fatty materials and some mineral salts. Of these, the
most important for leather making is the protein. This protein may consist of many types. The
important ones are collagens, which on tanning, gives leather.
Water Protein Fats Mineral salts Others
60-70% 19.2-32.75% 1.5-12.25% 0.36-.5% 0.5%
Structural Protein Non-Structural Protein
Elastin Collagen Keratin Albumens, Mucins,
0.3% 29% 2.0% Globulins. Mucoids.
1.0% 0.7%
Figure 2: Composition of hides and skins (Sharphouse, 1995).

3.3 Different Layers of raw hide / skin
Leather is nothing but a natural fibrous protein sheet made from rawhide or skin through
tanning and finishing in a tannery. Rawhide or skin has the following layers---
Epidermis.
Corium mirror.
Corium major.
Hypodermis.
Approx. 1% of rawhide thickness
. 20 to 50 %
Derma layer
which is 85 %
of the total raw Approx. 80 to 30%
hide thickness
Approx. 15 %
Figure 3: Layers of a hide (Sharphouse, 1995).
To convert the raw hide or skin to leather, the epidermis layer is first removed (except in the
case of fur tanning) through pre-tanning operations like liming, bating etc. the appreciable
amount of hypodermis layer is also removed during fleshing. The remaining section called
Epidermis
Corium minor
Corium major
Hypodermis

derma is tanned. Leather is therefore, made from derma only which have mainly two layers,
corium minor and corium major.
3.4 Anatomy of Hide / Skin
Figure 4: Anatomy of hides and skins (Sharphouse, 1995).
Hide / Skin can be divided mainly into two principal layers---
The epidermis or outer layer, also called „ Stratified epithelium‟; Cuticle.
The corium or the inner layer, also called Dermis, Cutis vera, True skin.
The epidermis or outer layer.
It is comparatively thinner than corium, covering about 1-2% of the total thickness of the
entire skin. Broadly, it is divided into two layers of cells

1.) The outer or horny layer
2.) The inner or soft layer (also called malpighian layer).
Hair is the typical epidermal structure and is entirely a product of the epidermis. The cells of
the epidermis dip down into the body of the dermis and form a hair pocket or follicle in which
the hair grows (Dutta, 1973).
Corium.
This is the main layer of the hide or skin constituting about 98 % of its thickness. It is
composed of fibers, which occur in bundles. The fibers consisting mostly of collagen form a
three-dimensional fiber wave.
The corium is divided into two layers of different structure -
1.) The grain layer or papillary layer.
2.) The corium proper or reticular layer.
1.) The grain layer
The grain layer has been called by Wilson ‗ the thermostat layer‘ because it keeps the body
temperature constant through the action of sweat and flat glands present in it. The grain layer
consists of Erector pile muscle, Sebaceous glands / fat glands, Sweat glands.
Erector pile muscle-----It is attached to each hair follicle by elastic fibers. It passes just below
the sebaceous gland (fat gland) and extends oblique to the grain membrane (Dutta, 1973).
Sebaceous glands / fat glands------These glands are connected to the hair follicle my means of
capillary ducts through which the oily matter of the glands flows by the pressure of the
erector pile muscle when they contract.

Sweat glands - These glands are made up of coiled tubes with spiral ducts and control the
rise of the body temperature, causing evaporation of the perspiration produced by heat (Dutta,
1973).
2.) The corium proper
This is below the grain or thermostat layer constituting about 75-90 % of the total thickness.
It is also reticular layer because of its netlike woven structure. The corium proper consists of
Yellow / elastic fibers, Collagen, Flesh
Yellow / elastic fibers - These are present mainly in the thermostat layer of the corium. They
are made of elastin protein substance. The yellow fibers do not gather into bundles, as in the
case of collagen. Yellow fibers also present to some extent in the flesh layer and associated
with blood vessels.
Collagen-----This is the main constituents of the corium. It is high content of praline,
hydroxyproline and glycine. Collagen can react with the tanning agent to form a leather
substance. It is mostly insoluble in natural solvent and water.
Flesh-----A thin layer appended to the corium is called flesh or adipose layer. Although it is
not a part of the hide from the tanner‘s standpoint. It is the loose connective tissue lying
between the hide and the actual body of the animal (Sharphouse, 1995).
3.5 Mechanism of putrefaction of raw hides and skins.
Putrefaction of hides and skins means decay of protein and other hide / skin materials due to
bacterial actions. So long as an animal is alive, the life force of the animal saves the hides /
skins from bacterial attack but as soon as the animal is dead, the life force is off and the
proteolytic and other bacteria attack the hide (skin) materials and finally putrefy them and

leaving different organic bad smelling compounds like indole, amines, ammonia, sulphides
etc. proteins are food for proteolytic bacteria.
During putrefaction not only protein but other compounds like fats and oils, carbohydrates,
pigments etc also get composes. Different types of bacteria attack different substrates, e.g.
proteolytic bacteria attack the protein.
Protein molecules are so big in diversion that bacteria cannot attack them unless the protein
molecules are broken into small pieces, which is done by proteolytic enzymes secreted by
proteolytic bacteria and many types of mold. Proteolytic enzymes break the
-CO-NH- linkages of polypeptide chains. Thus, the mechanism of putrefaction of hides and
skins can be explained as below—
1. Hide / Skin proteins + Proteolytic enzymes Smaller protein molecules +
Proteolytic enzymes.
2. Smaller protein molecules + Proteolytic bacteria
Indole, ammonia, sulphides, amines + acids + CO2 + H2O + N2 + O2 + H2 etc. (Dutta, 1973).

3.6 Division of a Hide
Figure 5: Parts of hide or skin (Justin, 2013)
The dermis, which is made up of interwoven fiber bundles, is not uniform throughout its area
and cross section. The substance, the compactness, the feel etc are therefore different in
different regions of the hides. According to the qualities, the different regions of a hide have
been given different names, e.g., Butt, Neck, Shank etc.
In the trade, the raw hide or skin has been mainly divided into three regions namely,

1. Butt or Bend
2. Neck and
3. Flank.
The relationship among these three types of region of a hide or skin is as follows---
1.) Butt or Bend---------- Back + Shell + Butt edges.
2.) Neck-------------------Cheeks + Head + Shoulder
3.) Flank-------------------Belly + Flanks + Fore and Hind Shank.
The average percentage areas of these three regions are as follows---
1.) Butt or Bend---------45 to 50 % of total hide area.
2.) Neck-------------------20 to 25 % of total hide area.
3.) Flank------------------20 to 25 % of total hide area.
Other regions which are trimmed off equal to 15 to 0 % of total hide area. The divided
portion along the backbone of a hide or skin is called the side.

3.7 Leather Tanning
The process of converting raw hides and skins into leather is called tanning.
Figure 6: General Flow Diagram for Leather Tanning and Finishing Process.7
7
Science Education Resource Center (2009) Leather Tanning. Retrieved on September 07, 2015 from
http://serc.carleton.edu/woburn/issues/tanning.html

Operations carried out in the beam house, tan yard, and post-tanning areas are often referred
to as wet processes, as they are performed in processing vessels such as drums. After post-
tanning, the leather is subjected to dry finishing operations. Processes employed in each of
the above categories change depending on raw material used and the desired final product.
Therefore, the environmental impacts vary from tannery to tannery (Sharphouse, 1995).
3.8 The Tanning Process
Hides and skins are primarily composed of water, protein and fatty materials. The most
important protein in the production of leather is collagen, which makes up approximately
29% of the mass of a freshly flayed hide. The collagen desirable for tanning is found in the
grain and reticular layers where it is "intimately woven" in a three-dimensional mesh that is
think and tightly woven in the grain and coarser and stronger in the reticular layer.
After slaughter, hides and skins must be temporarily preserved for shipment and storage prior
to tanning. The most common commercial method of preservation is to cure the hides and
skins using salt to produce a dehydrated wet-salted or dry-salted material.
The majority of leather (almost 90%) is tanned with chromium and is therefore commonly
used as the basic format when trying to understand leather production. Other methods of
tanning will have significantly different production flow although if the material to be
produced is without hair, wool or scales, the preparation and isolation of the collagen in the
beamhouse processes will remain largely similar. The use of drums as process vessels but
paddles, pits and mixers are also common. Leather manufacture is usually divided into three
or four zones but this may vary slightly according to processing and the perspective from
which it is viewed.

Preparation of the Raw Pelt for Tanning
Tanning primarily involves the reaction of tanning chemicals with collagen, raw hides
contain a number of undesirable components, which are commonly removed prior to tanning.
Approximately 75% of the mass purchased as raw material is removed as polluting solid or
liquid waste. Preparation of the raw pelt includes the processes from soaking to pickling.
Soaking
Soaking is usually the first process encountered in the tannery, as the previously dehydrated
raw material must be carefully rehydrated before it can be subjected to extended mechanical
action. Water is also the vehicle for both chemical penetration and removal, and is a
necessary prerequisite for most of the processes to follow. Soaking also assists in the removal
of curing agents, non-structural proteins and fats. The flesh layer is removed mechanically to
aid an even and full penetration of the chemicals to follow. Fleshing is commonly done after
slaughter, after soaking, or after liming.
Unhairing and Liming
The majority of leathers produced are treated in order to remove the hair or wool to leave the
characteristic pattern of the grain surface (analogous to wood grain). Conventionally, the
hides or skins are treated with sodium sulphide and hydrated lime to destroy the keratinous
material of the epidermis and hair or wool. Fats are hydrolysed due to the increased pH and
the skin structure swells as water is drawn into the fibre network to form a turgid, open-
structured, translucent, jelly-like material.
Deliming and Bating
Weak acids are used to lower the pH and to reduce swelling which causes the water to flush
out any impurities with it. The skin becomes flaccid and is treated with proteolytic bating
enzymes to clean the grain and make the pelt smooth and silky.

Pickling
The bated pelts are finally treated with acid (commonly sulphuric and/or formic acid) to
obtain the desired pH for optimal penetration of the tanning agent, and with salt, to suppress
swelling when the acid is added. At this stage, the isolated collagen, termed the pickled pelt,
is ready for a pretannage or man tannage.
Pretanning, Tanning and Retanning
This includes processes from pretanning and tanning through to retaining via samming,
splitting, shaving and neutralization as a preparation for the dyehouse.
Pretanning
The pickled pelt may be lightly tanned prior to the main tannage to improve the penetration
and distribution of the tanning chemicals to follow, to add specific properties into the leather
or to stabilize it for mechanical operations such as shaving.
Tanning
The main tannage has the primary function of producing an utilizable material resistant to
microbial attack. The most common chemical used in tanning are chromium tanning salts,
vegetable tannins and more recently glutaraldehyde. After the tanning agent has penetrated
the collagen structure and distributed satisfactorily, it must be irreversibly bound to the
collagen (e.g. a process called basification, in which the pH is raided, is used to bind
chromium and glutaraldeyde tanning agents to the collagen).
Mechanical Operations
At some point during production, the leather is split longitudinally to yield an upper grain
split and a lower flesh split of desired thickness. In the production of chromium tanned
leathers, this process is most commonly performed after basification and samming. The
material is then shaved to give a more accurate and even thickness depending on the

requirements for the end products e.g. shoe upper (1.8 mm), garment (0.9 mm) or upholstery
leathers (1.1 mm) (The Leathersellers' Company).
Neutralization
The mechanical operations generally squeeze water out of the leather, so prior to further
treatment a wetting back and washing process is used to rehydrate the leather and to remove
dirt, shavings or grease that may have been picked up. The majority of the chemicals still to
be added to the leather are anionic in nature, whereas the tanned collagen at low pH tends to
be cationic in nature. Neutralization is a process in which the pH is raised and chemicals are
added to reduce the stringency of the leather to anionic chemicals such as retanning agents,
dyes and fatliquors.
Retanning
The tanned leather is subjected to additional tannages with similar or new tanning materials.
These agents may be used to lighten the color of the leather, to produce a feeling of fullness
and to aid in the penetration of dyes. The choice of pretanning, tanning and retanning
chemicals is dependent on the properties desired in the final leather, and therefore, on the
properties required in the final leather product.
Dyeing, Fatliquoring and Drying
This stage includes preparing the retanned material for finishing by processing through to
dried crust.
Dyeing
Chromium tanned leather is blue in color and must be dyed to obtain the desired color. The
dye acts as a base color for finishing, and the depth of dye penetration and leather color are of
great importance (Karabay, 2008).

Fatliquoring
Chromium tanned material dries out hard and crusty and is unsuitable for most purposes.
Small quantities of oil, present as emulsions known as fatliquors, make a significant
difference to the handle, i.e. the fullness, softness and flexibility, among other factors.
Drying
The retanning, dyeing and fatliquoring chemicals are allowed to penetrate and distribute
within the collagen fibre structure before the pH is lowered and the astringency causes them
to "fix" to the tanned material. The final binding of chemicals is encouraged by the drying
process. Batches of leather are commonly toggle dried on frames in heated tunnels for four to
six hours or are vacuum dried individually for two to ten minutes. Drying is usually followed
by buffing, conditioning and staking or milling. The resultant curst material is resistant to
microbial attack and contains all the leathering properties desired of leather and is ready for
finishing.
Finishing
A finish process and finishing chemical must be carefully designed and "married" with the
production of the curst to ensure compatibility. The finish may be required to hide defects, to
contribute to the leather beauty and properties and to provide fashion effect. Resins,
pigments, dyes, handle modifiers, fillers, dullers and other chemicals are added in layers to
the surface of the leather by spraying, roller-coating, curtain-coating or by hand. Heated
hydraulic or roller presses are used to produce smooth or patterned leathers, depending on
customer requirements. Finishing finally completes the leather manufacturing process and the
area is then measured and the leather sent for dispatch to a product manufacturer to be turned
into shoes, clothing or upholstery (The Leathersellers' Company) (Karabay, 2008).

3.9 Waste produced during Tanning processes
Tanning industry is one of the oldest industries in the world. It is typically characterized as
pollutants generated industries which produce wide varieties of high strength toxic chemicals,
it is recognized as a serious threat due to high chemical levels including salinity, organic load
(BOD, COD), inorganic matter, dissolved, suspended solids, ammonia, total Kjeldahl
nitrogen (TKN), specific pollutants (Sulfide, chromium, chloride, sodium and other salt
residues) and heavy metals.
Over 273 tanneries at Hazaribagh process 220 MT of leather everyday resulting 7.70 million
liters of waste water and 88 MT of solid waste respectively.
Large quantity of water is used in tanning process of which 90 % of the water is discharged as
effluent. A part of the leather processing, solid and gaseous wastes are also discharged into
the environment. During the chrome tanning process, 40 % unused chromium salts are
usually discharged in the final effluents, causing a serious threat to the environment
(Chowdhury, Mostafa, Biswas, & Saha, 2013).
Wet Blue Stages
• Soaking
Liquid - Blood, flesh, proteoglycans (an ingredient of the leather) and unused sodium
chloride.
Solid - Flesh and hair.
Environmental Hazards - The solid wastes piled up on the street in front of the tannery
which cause disgusting smell. The polluted air often causes diarrhea, stomach problems and
nausea when it gets into human body.

Carbon dioxide, produced from sodium carbonate, increases the level of carbon dioxide in the
air. Inhaled excess Carbon dioxide may cause senselessness and is harmful for the lungs. The
tannery laborers are directly exposed to Carbon dioxide. They are exposed to other health
hazards including disgusting smell produced from the rotten wastes.
• Unhairing and Liming
Liquid -Unused calcium hydroxide, sodium sulfide and sodium bisulfide.
Solid - Fat, flesh and hair.
Gaseous - Sulfur dioxide and hydrogen sulfide.
Environmental Hazards---Maximum environmental pollution occurs at this stage of leather
processing. Hydrogen sulfide is a highly poisonous gas. It affects the human nervous system.
It can cause respiration difficulties, bronchitis, skin disease, headache, etc. With a raw smell
of rotten egg, hydrogen sulfide affects the membrane of the nose causing irritation.
Sulfur dioxide gas causes nausea, sinusitis, diarrhea, allergy, bronchitis, heart disease, blood
pressure and ear, nose and throat irritation. Hydrogen sulfide and sulfur dioxide produce
sulfuric acid vapor reacting with oxygen in the air. Sulfuric acid corrodes the brightness of
buildings and things made of tin, copper, brass, aluminum and gold ornaments. It perforates
the tin and iron bars become rusty. The coat of the ornaments disappears quickly. Hydrogen
sulfide is as toxic as hydrogen cyanide, Death causes instantly at higher level of it. It also
weakens metal roofing, girders and metal building supports. Aquatic life can be also
seriously damaged.
• Fleshing
Solid - Waste flesh and fat called fat flesh.

Environmental Hazards - Solid wastes are piled up on the road or by the drains. The rotten
flesh generates disgustingly foul smell. Flies carry germs from the rotten flesh to the
foodstuff particularly in the adjacent hotels. The solid wastes are finally disposed of into the
low land of Hazaribagh (Glorious Sky Foundation, 2015).
• Deliming and Bating
Liquid - Unused sodium meta bisulfite, used sodium sulfite, unused salts of ammonia and
unused Pancreol EG-98 and melted fat.
Gaseous - Sulfur dioxide and ammonia gases.
Environmental Hazards - Poisonous sulfur dioxide gas produced from the unused sodium
meta bisulfite causes burning in the eyes, nose and throat, high blood pressure and bronchitis.
Ammonia gas causes headache, nausea and drowsiness. The ammonia salts are harmful for
the reproduction of fish. The salt mixed with liquid waste runs into the Buriganga river. The
tannery labors and employees are directly exposed to the poisonous gas.
• Pickling
Liquid - Unused sulfuric acid, formic acid and sodium chloride.
Gaseous - Chlorine.
Environmental Hazards -Sulfuric acid and formic acid are very strong. These acids wounds
on the skin and may cause cancer ultimately. Chlorine gas, created at this stage, may cause
death.
• Chrome tanning
Liquid - Unused chromium sulfate, sodium bicarbonate, sodium carbonate and sodium
formate.

Environmental Hazards--- Unused chromium sulfate (chromium is trivalent here) is
extremely harmful. Under pressure and heat trivalent chromium transforms into hexavalent
chromium (Chromium +6). This causes wounds on the skin. Contaminated by chromium, the
old wounds take longer time to heal. Long term chromium contamination may cause
cancerous diseases.
• Pre-crusting Operation
Solid - Shaving dust (tiny pieces of leather)
Environmental Hazards - Different chemicals are used at different stages of processing
leather. The residue of some chemicals remains in the leather. During shaving, molecules of
these chemicals, mixed with the dust and particles of leather, float in the air and enter into the
lungs with breath. These may cause bronchitis. The shaving machine operation is directly
exposed to the shaving dust.
Some labors take the shaving dust and leather waste for cooking their meals. When burnt
these dust and leather generate hexvalent chromium in the air. Chromium is highly
dangerous for the human body. It may cause lungs cancer.
Crusting
• Rechroming
Environmental Hazards - Unused chromium sulfate (chromium is trivalent here) and the
hexavalent form of chromium are the main hazardous substances generated in this stage.
Retanning
Liquid - Unused organic acids, resin, polymer and fat.
Solid - Non-soluble extracts.
Environmental Hazards - Unused organic acids are harmful for skin.

• Dyeing
Liquid - Unused different dyes, mixing agents, substances produced from condensation of
urea and formaldehyde, naphthalene and formaldehyde.
Environmental Hazards - The labors inside the tannery factories regularly inhale the dyeing
agents. Unused organic acids and the dyeing agents remaining in the drums after dyeing are
discharged into the drains. The waste ultimately deposits in the low land of Hazaribagh much
of which finally runs into the Buriganga river. As a result, the Biological Oxygen Demand
(BOD) in the river raises causing oxygen shortage to the aquatic life. From Buriganga the
waste also spreads into other rivers.
Figure 7: Used dye liquor mixing with the drain water.
Unused fixing agents are extremely harmful for human health. The dyes containing benzidine
(C6H4NH2)2 is strictly banned in leather processing, because it is extremely hazardous.
• Fat liquoring
Liquid - Unused oil and liquid fat.
Environmental Hazards - The oil and the fat contain many substances, which are harmful
for the human body. These substances irritate eyes and noses. Long term exposure to these

may cause cancer. Besides, the nervous system may also be affected. The unused oil and fat
run into the drains and finally into the low-lying land and the Buriganga river.
• Finishing Stage
Liquid - Unused liquid pigment, unused dye, unused emulsifying agent and binder and
adhesive.
Solid - Buffing dust, finishing cuttings.
Gaseous - Ammonium hydroxide and formaldehyde, nitro cellulose, polyurethane vapour.
Environmental Hazards - Finishing ingredients spread in the air through spray gun.
Poisonous compounds in these ingredients include ammonium hydroxide and formaldehyde.
The labors inhale those gases.
Figure 8: Leather finishing in the open air.
Nitro cellulose is also harmful for human health. Buffing is done to smooth out the leather.
Finest fragments of leather permeate the air and who inhale may get possibility to cancer.

Figure 9: Buffing dust on the street
The buffing waste is also disposed of into the drain. Sometimes it is piled on the street
(Glorious Sky Foundation, 2015).
3.10 The polluting features of the tannery waste on different surfaces
1. On the surface water: The disposal of tannery wastes into any surface water affects its
quality in varied ways. The high organic content interferes with the oxygen content of the
Figure 10: Tannery waste mixing with drain water

receiving water. The alkalinity and sulfide content stakes the aquatic life. Presence of
chromium III despite of its significantly less toxicity than Cr (VI), makes the aquatic
environment toxic to the biota - the other aspect of pollution. Presence of lime, hair and
fleshings etc make the water turbid. The coloring substance present and dissolved organic
content alters the taste and odor. Oily substance affects the aeration of water and other
indirect effect on the survival of the aquatic life.
.2. On land: The fertility of land is affected, as said, due to the presence of sulfide in the
effluent. Moreover the Cr content influences the plant metabolism.
Figure 11: Tannery waste on land. Figure 12: Tannery effluent mixes with sewer.
3. On ground water: Due to disposal on land the effluent percolates through and infects the
ground water. The high chloride and dissolved solids content in the subsurface water of a
river in the tannery-infested area is indicative of the effect of tannery wastes.
4. On sewers: Disposal of tannery wastes into the sewer cause the clogging of the sewers.
The suspended solids like lime, hair, fleshing, etc. Settles at the bottom of the sewer thus
choking the water flow.

Table 1 : Potential chemical and gaseous contaminants produced at different stages of leather
processing8
Leather processing stage Water pollutants Air pollutants
Soaking/Liming BOD, COD, SS, DS,
Sulphides
H2S
Deliming & Bating BOD, COD, SS NH3
Degreasing BOD, COD, DS
Pickling/Tanning BOD, COD, DS, Acids, Salts Acidic fumes
Retanning/Bleaching/ Dyeing Acids, Salts, Chrome,
Chlorinated, phenols
Volatilized, chlorinated,
Phenolics
3.11 Chemicals used in Tanning process
In terms of toxicity and potential to cause a hazard it is a relatively straightforward task to
divide a typical list of chemicals used in tanning into the following groups:
1. High potential Hazard group
Acetic acid
Ammonia
Lime
Calcium hydroxide
Formaldehyde
Formic acid
Sulphides and hydrosulphid
Hydrogen peroxide
Oxalic acid
8
Mwinyihija, M. (2010). Ecotoxicological diagnosis in the tanning industry. New York: Springer.

Sodium chlorite
Sodium hydroxide (caustic soda)
Sulphuric acid, etc.
2. Moderate potential hazard groups
Aluminum sulphate
Amyl acetate ( as lacquer constituents)
Amyl alcohol ( as lacquer constituents)
Benzyl alcohol ( lacquer solvent)
Chromium salts (trivalent)
White sprite, etc.
3 . Low potential Hazard group
Alum oils
Acetone paraffin
Albumen pigment dispersion
Borax
Wetting agents
Fatliquor, etc.
3.12 Effect of Chemicals on Human Body
Acetic Acid (CH3COOH)
It is a clear, colorless liquid above 16 °C and colorless, ice like crystals below 16 °C. Has a
strong, pungent odour of vinegar. Hygroscopic. Combustible liquid and vapour. Vapour is

heavier than air and may spread long distances. Distant ignition and flashback are possible.
Harmful if inhaled or swallowed. Vapour is irritating to the respiratory tract. May cause lung
injury--effect may be delayed. Concentrated solutions are corrosive to eyes and skin. Causes
permanent eye damage, including blindness, and skin burns, including tissue death and
permanent scarring. May be an aspiration hazard. Swallowing or vomiting of the liquid may
result in aspiration into the lungs.
Target Organs: Teeth, eyes, skin, mucous membranes.
Health Effect
Primary Route(s) of Entry: Inhalation and ingestion. Skin contact. Skin absorption.
Effect of Acute Exposure: May be fatal by ingestion, inhalation or skin absorption.
Eyes: Concentrated solutions are corrosive and can cause permanent eye damage, including
blindness.
Skin: The degree of irritation depends on the concentration of acetic acid and the length of
exposure. Highly concentrated solutions or pure acetic acid can cause corrosive tissue injury
with deep burns, tissue death and permanent scarring. Less concentrated solutions can cause
mild to severe irritation.
Ingestion: Causes severe corrosive injury to the gastrointestinal tract and stomach. Acetic
acid may be aspirated (inhaled into the lungs) during ingestion or vomiting. Aspiration of
even a small amount of liquid could result in a life-threatening accumulation of fluid in the
lungs. Severe lung damage (edema), respiratory failure, cardiac arrest and death may result.
Ingestion is not a typical route of occupational exposure.
Inhalation: Accidental inhalation of high concentrations may cause corrosive injury to the
respiratory tract, inflammation, nose and throat irritation, shortness of breath, cough,

wheezing, and reversible lung injury in people exposed occupationally. Effect may be
delayed.
Effect of Chronic Exposure: Repeated inhalation may cause pulmonary edema,
bronchopneumonia, or chemical pneumonitis. Prolonged or repeated exposure may cause
dermatitis, erosion of teeth, conjunctivitis and cumulative systemic injury. To the best of our
knowledge, the chronic toxicity of this substance has not been fully investigated (Seaster
Chemical Inc., 2014).
Ammonia (NH3 )
Ammonia or azane is a compound of nitrogen and hydrogen with the formula NH3. It is a
colorless gas with a characteristic pungent smell. Ammonia, as used commercially, is often
called anhydrous ammonia. This term emphasizes the absence of water in the material.
Because NH3 boils at −33.34 °C (−28.012 °F) at a pressure of 1 atmosphere, the liquid must
be stored under high pressure or at low temperature.9
Ammonia is not hazardous to health at concentrations typically found in the environment. At
higher concentrations ammonia can be harmful. The most common health effect is irritation
to the eyes, nose, or throat.
Primary Route(s) of Entry: Inhalation and ingestion. Skin contact. Skin absorption.
Effect of Acute Exposure: May be fatal by ingestion, inhalation or skin absorption.
blindness.
9
Wikipedia Web site. (2015) Ammonia Retrieved on September 07, 2015 from https://en.wikipedia.org/wiki/Ammonia

mild to severe irritation. (Seaster Chemical Inc., 2014)
If swallowed, ammonia will cause pain and burning in the throat and stomach.
If touched, ammonia can cause irritation or burns to the eyes or skin.
If breathed in, ammonia can irritate the respiratory tract and can cause coughing, wheezing,
and shortness of breath. Inhalation of ammonia can also cause nose and throat irritation.
People can smell the pungent odor of ammonia in air at about 5 parts of ammonia in
a million parts of air (ppm).
According to World Health Organization (WHO), continuous exposure to 25 parts per million
(ppm) of ammonia in the air does not result in a significant increase in blood levels of
ammonia in the body.
According to the Occupational Safety and Health Administration (OSHA), the least amount
of ammonia which is found to be irritating to the eyes, nose and throat of the most sensitive
individuals is 50 parts per million (ppm). There is no evidence that ammonia causes cancer.
Frostbite can occur with exposure to anhydrous ammonia.
Exposure to very high concentrations of ammonia gas can cause pulmonary edema, upper
respiratory irritation, tearing of the eyes, increased pulse rate, and increased blood pressure.
Death has been reported after an exposure to 10,000 ppm for an unknown duration.
There is no evidence that exposure to the levels of ammonia found in the environment
causes birth defects or other developmental effect.

Because ammonia is a respiratory tract irritant, persons who are hyper reactive to other
respiratory irritants or are asthmatic, may be more susceptible to the inhalation of ammonia
(Health effects of ammonia, 2011).
Calcium hydroxide (Ca (OH)2)
Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the
chemical formula Ca(OH)2. It is a colorless crystal or white powder and is obtained when
calcium oxide (called lime or quicklime) is mixed, or "slaked" with water. It has many names
including hydrated lime, builders' lime, slack lime, Choona (word used in India, Pakistan
and Afghanistan), cal, or pickling lime10
.
Calcium hydroxide is the exothermic product of calcium oxide and water, according to
Darrell D. Ebbing and Steven D. Gammon's "General Chemistry." It has a strong base pH and
is used for many purposes, often under its more common name, slaked lime. The National
Institutes of Health warns that calcium hydroxide is also toxic and can introduce serious
health problems as a result of various types of exposure.
Health Effect
Ingestion
Accidental ingestion of calcium hydroxide can cause severe throat pain, a burning sensation
in the mouth, abdominal pain, vomiting, bloody stool or vomit, rapidly falling blood pressure
and collapse, according to the National Institutes of Health. This type of poisoning can also
make blood pH too alkaline, which can cause organ damage. Poison control or other
10
Wikipedia Web site (2015) Calcium Hydroxide. Retrieved on September 07, 2015 from
https://en.wikipedia.org/wiki/Calcium_hydroxide

emergency services should be contacted immediately if calcium hydroxide is accidentally
swallowed. Unless the victim is vomiting or exhibiting other symptoms that would make
swallowing difficult or unless directed otherwise by a physician or poison expert, he should
immediately be given water or milk to drink (Baum, 2013).
External Exposure
External exposure to calcium hydroxide can cause a variety of problems depending on the
exact location of the exposure and the strength of the calcium hydroxide solution. Exposure
to the skin can produce burns, painful irritation and necrosis, and exposure to the eyes may
cause severe pain and vision loss that can be temporary or permanent. If calcium hydroxide is
exposed to the skin, contaminated clothing should be removed, excess amounts of the
chemical should be wiped off and the affected skin should be flushed repeatedly with water.
Victims of calcium hydroxide exposure to the eyes should flush their eyes with water
continuously for the first 15 minutes, but all cases of external exposure should receive
immediate medical care. According to Absolute Astronomy, calcium hydroxide is commonly
used in no-lye hair relaxer products; the FDA warns that misuse of these products may cause
burning and damage to the hair and scalp (Baum, 2013).
Inhalation
Inhaling calcium hydroxide through the nose or mouth can also cause immediate, painful and
potentially life-threatening complications. Throat and nasal passages may become painful and
swollen, and the swelling may restrict airways, making breathing difficult or impossible. If
the calcium hydroxide particles are carried all the way to the lungs, this may further
complicate breathing. Victims of this type of exposure should be taken immediately to a fresh
air environment, and emergency services should be contacted right away. Administration of
oxygen and emergency respiratory assistance may be required. (Baum, 2013)

Chronic Exposure
According to the Material Safety Data Sheet (MSDS) on calcium hydroxide, chronic
exposure to the skin may also cause health problems. As calcium hydroxide is an active
ingredient in some hair relaxers, these symptoms could potentially arise as a result of
prolonged, regular use of those products. Dermatitis and severe skin irritation are common
symptoms of this type of exposure (Baum, 2013).
Formaldehyde ( HCHO)
Formaldehyde is an organic compound with the formula CH2O or HCHO. It is the simplest
aldehyde, hence its systematic name methanal. The common name of the substance comes
from its similarity and relation to formic acid. A gas at room temperature, formaldehyde is
colorless and has a characteristic pungent, irritating odor11
.
Potential Health Effect
Primary Route(s) of Entry: Inhalation and ingestion. Skin contact. Eye contact.
Effect of Acute Exposure: Corrosive to skin and mucous membranes. Irritant.
Eyes: Causes eye burns. May cause permanent eye damage, including blindness.
Skin: Causes skin burns, blisters and permanent scarring.
Ingestion: May be fatal if swallowed. Causes burns to the mouth, pharynx and
gastrointestinal tract.
11
formaldehyde. (n.d.). Definitions.net. Retrieved September 7, 2015, from
http://www.definitions.net/definition/formaldehyde.

Inhalation: May be fatal if inhaled. May cause severe irritation of the respiratory tract with
possible burns to the nose, throat and lungs. May cause coughing, shortness of breath, chest
pain, and delayed pulmonary edema.
Effect of Chronic Exposure: Prolonged or repeated inhalation may cause nosebleeds, nasal
congestion, erosion of the teeth, perforation of the nasal septum, chest pain, and bronchitis.
Prolonged or repeated eye contact may cause conjunctivitis. Prolonged or repeated skin
contact may cause sensitization dermatitis and possible destruction and/or ulceration. Chronic
ingestion may cause effect similar to those of acute ingestion (Seastar Chemicals Inc, 2011).
Formic acid (HCOOH)
Formic acid (also called methanoic acid) is the simplest carboxylic acid. Its chemical
formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and
occurs naturally, most notably in ant venom. In fact, its name comes from the Latin word for
ant, Formica, referring to its early isolation by the distillation of ant bodies12
.
Routes of exposure
Inhalation : Exposures may occur by inhalation. Formic acid‘s odor and upper respiratory
tract irritant properties generally provide adequate warning of hazardous concentrations.
Skin/eye contact : Most exposures occur by direct contact of the skin and the eyes with
liquid formic acid. Contact with the skin and the eyes causes severe burns which may be
delayed in onset.
Ingestion: Ingestion is rare in occupational settings.
12
Wikipedia, the free Encyclopedia (2015) Formic Acid. Retrieved on September 07, 2015 from
https://en.wikipedia.org/wiki/Formic_acid

blindness.
mild to severe irritation (Seastar Chemicals Inc, 2011).
Ingestion: Causes severe corrosive injury to the gastrointestinal tract and stomach. Acetic
acid may be aspirated (inhaled into the lungs) during ingestion or vomiting. Aspiration of
even a small amount of liquid could result in a life-threatening accumulation of fluid in the
lungs. Severe lung damage (edema), respiratory failure, cardiac arrest and death may result.
Ingestion is not a typical route of occupational exposure (Seastar Chemicals Inc , 2011).
Inhalation: Accidental inhalation of high concentrations may cause corrosive injury to the
respiratory tract, inflammation, nose and throat irritation, shortness of breath, cough,
wheezing, and reversible lung injury in people exposed occupationally. Effect may be
delayed (Seastar Chemicals Inc, 2011).
Effect of Chronic Exposure: Repeated inhalation may cause pulmonary edema,
bronchopneumonia, or chemical pneumonitis. Prolonged or repeated exposure may cause
dermatitis, erosion of teeth, conjunctivitis and cumulative systemic injury. To the best of our
knowledge, the chronic toxicity of this substance has not been fully investigated (Seastar
Chemicals Inc , 2011).

Hydrogen peroxide (H2O2)
Hydrogen peroxide (H2O2) is the simplest peroxide (a compound with an oxygen-oxygen
single bond). It is also a strong oxidizer. Hydrogen peroxide is a clear liquid, slightly more
viscous than water. In dilute solution, it appears colorless. Due to its oxidizing properties,
hydrogen peroxide is often used as a bleach or cleaning agent13
.
Eye: Contact with liquid is corrosive to the eyes and causes severe burns. Contact with the
eyes may cause corneal damage.
Skin: Causes severe skin irritation and possible burns. May cause discoloration, erythema
(redness), swelling, and the formation of papules and vesicles (blisters).
Ingestion: Causes gastrointestinal irritation with nausea, vomiting and diarrhea. Causes
gastrointestinal tract burns. May cause vascular collapse and damage. May cause damage to
the red blood cells. May cause difficulty in swallowing, stomach distension, possible cerebral
swelling and death. Ingestion may result in irritation of the esophagus, bleeding of the
stomach and ulcer formation (Seaster Chemicals Inc, 2004).
Inhalation: Causes chemical burns to the respiratory tract. May cause ulceration of nasal
tissue, insomnia, nervous tremors with numb extremities, chemical pneumonia,
unconsciousness, and death. At high concentrations, respiratory effect may include acute lung
damage and delayed pulmonary edema (Seaster Chemicals Inc, 2004).
Chronic: Prolonged skin contact may cause dermatitis. Lab experiments have resulted in
mutagenic effect. Repeated contact causes corneal damage (Seaster Chemicals Inc, 2004).
13
Wikipedia, the free encyclopedia (2015) Hydrogen peroxide. Retrieved on September o7, 2015 from
https://en.wikipedia.org/wiki/Hydrogen_peroxide

Hydrogen sulfide (H2S)
It is a colorless gas with the characteristic foul odor of rotten eggs; it is heavier than air, very
poisonous, corrosive, flammable and explosive. Hydrogen sulfide often results from the
bacterial breakdown of organic matter in the absence of oxygen, such as in swamps and
sewers; this process is commonly known as anaerobic digestion. H2S also occurs in volcanic
gases, natural gas, and some well waters. The human body produces small amounts of H2S
and uses it as a signaling molecule14
.
Potential Health Effect from exposure:
Eyes: Highly irritating. May cause eye pain and an increased production of tears.
Skin: None expected from contact with gas. Liquid may cause frostbite, but this exposure not
expected.
Inhalation: CNS injury can be immediate and significant . Mucous membrane and
respiratory tract irritant. High concentrations, even briefly, may cause dizziness, drowsiness,
tremors, pulmonary edema, and death. Acts as a chemical asphyxiant by paralyzing the
respiratory center. Lower concentrations will produce symptoms such as headache, dizziness,
excitement, staggering gait, diarrhea and dysuria. Fibrogenic to the lungs following acute
exposures complicated by bronchitis obliterans (EP Energy, 2012).
Ingestion: Route of exposure unlikely to occur.
Chronic Effect:
Chronic low exposures may cause conjunctivitis, photophobia, bronchitis and headaches (EP
Energy, 2012).
14
Wikipedia, the free encyclopedia (2015) Hydrogen sulfide. Retrieved on September 07, 2015 from
https://en.wikipedia.org/wiki/Hydrogen_sulfide

Oxalic Acid (H2C2O4 )
It is a colorless crystalline solid that dissolves in water to give colorless solutions. It is
classified as a dicarboxylic acid. In terms of acid strength, it is much stronger than acetic
acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C2O4
2−
), is a
chelating agent for metal cations. Typically, oxalic acid occurs as the dihydrate with the
formula H2C2O4·2H2O. Oral consumption of oxalic acid or prolonged skin contact is
dangerous15
.
Health effect
Target Organs: Kidneys, heart, eyes, skin, brain, nerves, mucous membranes. Oxalic acid is
corrosive to tissue and causes burns. Inhalation may cause severe respiratory tract irritation
with possible burns. May cause severe digestive tract irritation with possible burns. May
cause kidney damage. May cause eye and skin irritation with possible burns.
Harmful in contact with skin and if swallowed. Possible risk of harm to the unborn child.
Ingestion: Oxalic acid is toxic because of its acidic and chelating properties. May cause
burns, nausea, severe gastroenteritis and vomiting, shock and convulsions. It is especially
toxic when ingested. As little as 5 to 15 grams (71 mg/kg) may be fatal. Ulcerations of the
mouth, vomiting of blood, and rapid appearance of shock, convulsions, twitching, tetany, and
cardiovascular collapse may occur following ingestion of oxalic acid or its soluble salts.
Oxalic acid can bind calcium from the blood to form calcium oxalate, which can precipitate
in the kidney tubules and the brain. Renal damage may result as evidenced by bloody urine.
15
Wikipedia, the free encyclopedia (2015) Oxalic Acid. Retrieved on September 07, 2015 from
https://en.wikipedia.org/wiki/Oxalic_acid

Hypocalcaemia secondary to calcium oxalate formation might disturb the function of the
heart and nerves.
Inhalation: Harmful if inhaled. Can cause severe irritation and burns of nose, throat, and
respiratory tract. Inhalation of oxalic acid dust or vapor can also cause protein in the urine,
nosebleed, ulceration of the mucous membranes, headache, nervousness, cough, vomiting,
emaciation, back pain (due to kidney injury), and weakness.
Skin Contact: Causes severe skin irritation. Harmful if absorbed through the skin. Rare
chemical burns may occur from oxalic acid and may cause hypocalcaemia. Gangrene has
occurred in the hands of people working with oxalic acid solutions without rubber gloves.
The skin lesions are characterized by cracking of the skin and the development of slow-
healing ulcers. The skin may be bluish in color, and the nails brittle and yellow.
Eye Contact: May cause severe eye irritation. It may produce corrosive effect. May result in
corneal injury.
Chronic Exposure: Inhalation of oxalic acid dust or mist over a long period of time might
result in weight loss and respiratory tract inflammation. Rats administered oxalic acid at 2.5
and 5% in the diet for 70 days developed depressed thyroid function and weight loss.
Prolonged skin contact can cause dermatitis, cyanosis of the fingers and possible ulceration.
A study of railroad car cleaners in Norway who were heavily exposed to oxalic acid solutions
and vapors revealed a 53% prevalence of urolithiasis (the formation of urinary stones),
compared to a rate of 12% among unexposed workers from the same company.
Aggravation of Pre-existing Conditions: Persons with pre-existing skin disorders or eye
problems, or impaired kidney or respiratory function may be more susceptible to the effect of
the substance (Oxalic Acid Safety sheet, (n.d.)).

Sodium chloride (NaCl)
Sodium chloride, also known as salt, common salt, Table salt or halite, is an ionic
compound with the formula NaCl, representing equal proportions of sodium and chlorine.
Sodium chloride is the salt most responsible for the salinity of the ocean and of the
extracellular fluid of many multicellular organisms. As the major ingredient in edible salt, it
is commonly used as a condiment and food preservative16
.
Health Effect
Potential Acute Health Effect: Slightly hazardous in case of skin contact (irritant), of eye
contact (irritant), of ingestion, of inhalation.
Potential chronic health effect:
Carcinogenic effect: Not available.
Mutagenic effect: Mutagenic for mammalian somatic cells. Mutagenic for bacteria and/or
yeast.
Teratogenic effect: Not available.
Developmental toxicity: Not available. Repeated or prolonged exposure is not known to
aggravate medical condition (Science Lab.com, Chemicals & Laboratory Equipment, 2005).
Sodium hydroxide (NaOH)
Sodium hydroxide, also known as caustic soda, or lye, is an inorganic compound with the
chemical formula NaOH (also written as NaHO). It is a white solid, and is a highly caustic
16
Wikipedia, the free encyclopedia (2015) Sodium Chloride. Retrieved on September 07, 2015 from
https://en.wikipedia.org/wiki/Sodium_chloride

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