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Environmental Toxicity Question Paper

Environmental Toxicity

Course:Bachelor Of Science In Environmental Health

Institution: Kenyatta University question papers

Exam Year:2009

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF BACHELOR
OF SCIENCE (ENVIRONMENTAL HEALTH)

HEH 403:
ENVIRONMENTAL TOXICITY

DATE: Tuesday 22nd December, 2009

TIME: 2.00 p.m – 4.00 p.m

INSTRUCTIONS: Answer all questions in section ONE. In section TWO, answer

question ONE and any other TWO.

SECTION ONE
1 a)
Define environmental toxicology. Give an example of a study that would be

relevant to this field.

[3 marks]
b)
Define the following terms
i)
Teratogen

[1 mark]
ii)
Exenobiotic

[1 mark]
iii)
Mutagen

[1 mark]
iv)
Dose

[1 mark]
v)
Threshold

[1 mark]
2
a)
State what is meant by the terms LD50and LC50.
[2 marks]
b)
Explain the difference between toxins and toxicants. Give an example for
each.

[4 marks]
c)
Explain three (3) factors that determine the toxicity of a chemical.
[6 marks]

Page 1 of 2

SECTION TWO

1a) Giving examples, describe the following effects of toxicant mixtures. [8 marks]
i)
Synergism
ii)
Antagonism
iii)
Potentiation
iv)
Coalitive interaction
b) Describe the steps that constitute risk assessment.

[12marks]
2a)
Describe the term latency as used in
toxicology.

[2 marks]
b)
Explain how latency challenges environmental toxicologists when trying to detect
hazards
associated
with
exposures.

[5 marks]
c)
Describe the process of toxic kinetics.

[8 marks]
3.
Write short notes regarding Cadmium and Mercury environmental toxicants under

the following subtitles.

[15 marks]

a)
Possible sources of exposure

b)
Modes of entry into the body

c)
Two major health effects

d)
Name of associated disease.
4.
Discuss the three major methods used in testing toxicity of chemicals and drugs

before they are marketed for both domestic and industrial use. [15 marks]
5a)
Describe phases of cancer development after exposure to carcinogenic substance.

[10marks]
b)
What is typical for each of these phases and for the carcinogenic chemicals

acting in these phases.

[ 5marks]

Page 2 of 2

Environmental Toxicity Question Paper

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