This document discusses two major gas leak incidents - the Bhopal gas tragedy of 1984 and the Vizag gas leak of 2020. It then discusses the concepts of ecotoxicology and how toxic substances can transfer and accumulate in the environment. Specific topics covered include biomagnification, bioconcentration, bioavailability, and the use of factors like BCF, BTF, BAF and BMF to measure bioaccumulation. Heavy metal pollution in Mumbai's Mithi River is given as an example. The science dealing with chemical uptake, movement, and effects in the environment is identified as chemodynamics. Biodegradation of xenobiotic compounds is also discussed.

1. Sudeshna Mandal
PG Sem III

2.  Case Study-1 :Vizag Gas Leak Tragedy
 Case Study-2:Bhopal Gas Leak Tragedy
 Occurance:3rd December;1984
 Place of Occurance:Bhopal;Madhya Pradesh,India
 Incident: Toxic gas MIC(Methyl Isocyanate) leaked from
pesticide plant ;Union Carbide Corporation.
 Effects on environment and human health:More than
500000 people affected and more than 40,000 people died
of choking, reflexogenic circulatory collapse and pulmonary
oedema.The stillbirth rate and neonatal mortality rate
increased greatly.
 Occurance: 7thmay;2020 at 3 am
 Place of Occurance: Visakhapatnam;Andhra Pradesh,India
 Incident:Toxic gas Styrene leaked from LG Polymers Pvt.Ltd.
 Effects on environment and human health: killed 12
people;people living near the facility and those affected by the gas
leak were facing difficulties in breathing, rashes, irritation of the
throat, sour eyes, vomiting. Many animals and people were also seen
fainting on the road.

3.  Case Study-3 : Itai-Itai Disease
 Case Study-4:Minamata Disease

4. The study of the effects of toxic substances on ecosystems is known as
Ecotoxicology.
 Ecotoxicological Effects:
 Transfers of toxic substances among
the major evironmental spheres:

5. The science that deals with these aspects of chemical release and uptake, movement,
degradation, and effects is called chemodynamics.
Air Water Food Soil
Biomagnification :
Bioavailability
Bioconcentration
Bioaccumulation

6. Biomagnification of DDT

7. TOXICANTS
 Heavy metals
 Nonmetallic
inorganic species
 Metalloids
 Persistent organic
toxicants
 Gaseous toxicants

8. Heavy Metal Pollution in Mithi River of Mumbai

9. of pesticides

10.  Bioconcentration Factor
(BCF)
 Biotransfer Factor(BTF)
 Bioaccumulation Factor
(BAF)
 Biomagnification Factor
(BMF)
Graph of bioaccumulation factors of Triclosan for fish. G. catla from the
Kaveri River, India

11.  Xenobiotic compounds are usually attacked by enzymes whose primary function is
to react with other compounds, a process that provides neither carbon nor energy
called cometabolism
 Biodegradation is a natural and complex
process of decompositiion facilitated by
biochemical reactions.
 Biochemical aspects of Biodegradation
• Metabolism
• Biotransformation
Cometabolism

12.  Factors in Biodegradation

13. EFFECTS OF TOXICANTS ON ECOSYSTEMS
• Sublethal effects
• Pollution-induced community tolerance

14. References
1. Connel, D.W., Bioaccumulation of Xenobiotic Comounds, CRC Press, Boca Raton,
1990.
2. Connell, D.W. et al., Introduction to Ecotoxicology, Blackwell Science, Malden,
MA., 1999.
3. Forbes, V.E., Ed., Genetics and Ecotoxicology, Taylor & Francis, Philadelphia,
1999.
4. Environmental Management: Text and Cases by Bala Krishnamoorthy
5. https://www.downtoearth.org.in
6. https://www.who.int/heli/risks/toxics/chemicals/en/