Welcome to Dr. Bill's Environmental Toxicology page.

Interactions of chemicals:
Types of interactions
1)  additive 2 + 2=4 - two organophosphates simultaneously used will depress cholinesterase equal to the additive concentration of each agent.

2)  synergistic effect 2  + 1=20  - carbon tetrachloride's hepatotoxicity is increased by the presence of alcohol.

3) potentiation 0 + 2=10. -  A compound does not have a toxic effect on a certain organ or system, but when added to another chemical it makes the latter much more toxic.

Example: A steady diet of corn oil potentiates the effect of incomplete carcinogens. Isopropanol    carbon tetrachloride, the hepatotoxicity is greater than carbon tetrachloride alone.

4)antagonism 2  +  2 =1. Two compounds administered together, interfere with each other's actions or one interferes with the action of the other chemical. Many of these principles are used in the design of antidotes in clinical toxicology or poisoning of humans.

a) functional antagonism - two chemicals produce opposite physiological effects.
Barbiturate intoxication results in a fall in blood pressure is antagonized by iv administratioon of vasopressors such as norepinephrine.

b) chemical antagonism - Interference with the normal chemical transformation of the chemicals so less toxic agent is available. A chelator binding to metal ions and decreasing toxicity.

c)dispositional antagonism - compound affects the absorption, distribution or excretion of the other compound so that less toxic compound reaches the target organs.

d) receptor antagonism - when two chemicals compete to bind to the same receptor. Naloxone treats respiratory depressive effects of morphine by competitive binding to same receptor.

Toxicity rating chart
probable lethal oral dose for humans
toxicity rating or class
1. practically nontoxic
2.slightly toxic
3.moderately toxic
4.very toxic
5.extremely toxic
6.supertoxic

>15 g/kg
5-15 g/kg
0.5-5 g/kg
50-500 mg/kg
5-50 mg/kg

more than 1 quart
between pint and quart
between ounce and pint
between teaspoonful and ounce
between 7 drops and teaspoonful
a taste (less than 7 drops)

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