Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 6.6. 
Paracelsus 
1493-1541. 
Paracelsus stated that 
the plant or animal 
venoms toxicity 
is determined by 
specific chemicals. 
He first described the 
correlations between 
dose levels and the 
body’s response to them 
and showed that small 
doses of substances can 
be harmless or even 
beneficial, while high 
doses of the poisonous.
Several types of doses are 
distinguished:
 
Œ contact dose – the 
amount of a substance 
taken in from the 
environment;
 
Œ absorbed dose – the 
actual amount of a 
substance that enters 
the body;
 
Œ total dose – the sum 
total of separate doses.

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6. Action of toxic substances in the environment – basic concepts of ecotoxicology 
 105
Permanent damage
Reversible damage
Dosage
Death
LD
50
a
b
0
Reaction to the substance
Homeostasis
The effect of a substance on a living organism depends on the 
properties of the substance, the age and sex of the organism affected 
by the substance, the duration of action and recurrence of dose, the 
way the substance enters the body and the transformation of the 
substance in the environ ment and the body. For example, the effect 
of  such  a  toxic  substance  as  dioxin  on  different  organisms  varies 
greatly, and the nature of its toxic action depends on the sex of the 
organism used for testing purposes.