Biogeochem - ecotoxicology

Question 1

What are the types of toxicity?

Answer 1

Economic
Forensic
Environmental

Question 1

what is toxicology

Answer 1

the quantitive study of the effects of substances on living things and the environment

Question 2

What is economic toxicology?

Answer 2

Deliberate use of a toxicant to produce harmful effects on target organism
- Eg Insecticides

Question 3

what is forensic toxicology?

Answer 3

Medical and legal aspects of the adverse effects of harmful substances and stressful conditions on humans

Question 4

what is environmental toxicology

Answer 4

The study of contaminants and pollutants and their harmful effects on the biosphere

Question 5

give an example of a toxin in the environment

Answer 5

Arsenic
DDT

Question 6

What forms of arsenic present in in the environment?

Answer 6

As3+ (most toxic form)

As5+

Question 7

What conditions do you find As3+ in

Answer 7

anoxic conditions

Question 8

what can the introduction of a toxin lead to?

Answer 8

biochemical changes
physiological changes
whole organism responses
population changes
community composition
ecosytem impacts (eg collapse)

Question 9

What is the difference between essential and non-essential elements

Answer 9

Essential
- needed for life
- always present in healthy living tissue
- deficiency symptoms when depleted

Non-essential
- no relevant or beneficial function for life

Question 10

list examples of essential elements

Answer 10

Na
Mg
Ca
P
K
N

Question 11

list examples of non-essential elements

Answer 11

Pb
Hg (mercury)
Cd
Li
He

Question 12

why is dosage important?

Answer 12

it is the most important determining factor to consider whether a substance will cause injury

Question 13

what is a dose?

Answer 13

the amount of a substance to which a living thing is exposed relative to bodyweight (mg/kg)

Question 14

what shape is a dose effect/response curve and what are the 3 areas on it?

Answer 14

S shaped

• no effect rage
• range of increasing effect with increasing dose
• maximum effect range

Question 15

how do you conduct traditional toxicity testing?

Answer 15

1) expose test organisms to given conc of toxin

2) measure how long it take for 50% of the population to die

Question 16

Sublethal effects of toxins

Answer 16

Inhibitory effects (eg growth, reporduction and respiratoin)

behavioural changes (feeding, migration, swiming)

morphological (eg colouration, tissue changes, vertebral damage)

genetic effects

Question 17

what is the mean median time?

Answer 17

the average time it takes for 50% of the population to die

(LT50)

Question 18

what is the median lethal dose?

Answer 18

the concentration of a toxic at which 50% of the test organisms are killed in a specified time

(LD50)

Question 19

differences between homogenous and heterogeneous toxicity curves

Answer 19

Homogenous
- S shape with steep dose-response
- individuals in the pop react in a similar way

Heterogenous
- shallow dose-response curve
- some individuals are more sensitive than others

Question 20

What is an effective concentration / effective dose

Answer 20

Th concentration of a toxin at which 50% of the test organisms suffer a specified sublethal effect within a specified time

EC50 or ED50

Question 21

Properties of a toxin influencing toxicity

Answer 21

Physical state
- the state a toxin exists in can determine its bioavailability

chemical state
- some chemical states are more toxic than others

interaction with other toxins
- additive, antagonism (interference) or synergism

Question 22

what is the most toxic chemical that we know of

Answer 22

Clostridium botulinum

Question 23

Exposure routes of toxins

Answer 23

• ingestion
• inhalation
• skin absorption

Question 24

What is antagonistic toxicity

Answer 24

chemicals counterbalance each other by exerting opposite effects

Question 25

How does arsenic pose a threat as a toxin in the environment

(hint: links to structure)

Answer 25

Cells will take up arsenic 5+ as it is structurally similar to phosphate. Once in the cell, the cell knows it is toxic but can’t get rid of it otherwise it will get rid of all its phosphate. The cell then converts As5+ into As3+ (which is more toxic) which enables the cell ti distinguish between phosphate and arsenic and then get rid of it

Question 26

Environmental factors influencing toxicity

Answer 26

• Oxygen concentration and elemental solubility
• Organo-complexes (eg when in a compound with other groups can become ore toxic)
• Salinity (eg osmosis)
• Water hardness (mineral content)
• pH
• Temperature

Question 27

Biological factors influencing toxicity

Answer 27

• Genetic constitution
• Species
• Age
• Life cycle
• Gender
• nutritional state
• metabolism
• excretion

Question 28

What is bioaccumulation?

Answer 28

higher concentration of toxin inside organism relative to surrounding environment because intake rates exceed the organisms ability to remove the substance