Basic toxicological principles

Principles of toxicology

1. Prof. Hina Sarwar Msc Zoology Topic:- BASIC TOXICOLOGICAL PRINCIPLES

2. Primary goal:- The primary goal of all toxicological investigations is “to know the relative toxicity of the substance with a view to determining its position among other toxic substances whose toxicity are already known”. In other words it is important to determine whether a substance is more or less toxic relative to other known toxic agents.

3. Principles:- Basic toxicological principles are: Cause-effect relationship:- The effect or response in question is clearly a direct or indirect result of the exposure of the organism to the toxic agents

4. Cont. 2. Dose-response/concentration-response: The effect is a result of the toxic agents reaching and interacting with the site of toxic action in or on the organism. The amount of toxic agent reaching the site of toxic action is some function of the exposure of the organism to the toxic agent. The magnitude of the effect is proportional to the amount of toxicants reaching the site of toxic action.

5. Factors effect dose:- Intake How much you are exposed or you take into the body Type of exposure Ingestion, Inhalation or by dermal absorption Time How long you are exposed

6. Cont.

7. 3. Quantified effect:- Effect can be measured and quantified in a reproducible way that is relevant to the toxic processes under examination.

8. Causality:- Causality is a critical toxicological principle as, for quantitative purposes, it must be reasonably certain that there is a causal relationship between the observed response and the presence of toxic agent. However, there may be some doubt about the identity of the chemical, which may have changed during the exposure, the actual exposure concentration in the water, and the specificity of the response, because aquatic organisms may respond similarly to a variety of stresses.

9. Cont. Thus, until proved, it is only a reasonable working presumption that the effect or response being observed is a result of exposure to the known concentration of chemical.

10. Lethal effect Chemical substances can have undesirable or distinctly harmful effects when taken up by an organism in sufficient amount over short time period. When taken up by organism in small amount over long time period.

11. Factor which determine nature(harmful or safe) No chemical is completely safe and no chemical is completely harmful. One factor that determine whether a chemical agent is potentially harmful or safe is the relationship between the conc. Of the chemical and the duration of the exposure.

12. In mammalian/aquatic toxicology:- In mammalian toxicology the key principle that measure the severity of the response is termed the Dose response relationship as toxicant is usually introduced orally as a bolus or dose into the body of the organism. In aquatic toxicology where exposure is usually via waterborne concentration of the toxicant, this basic principle is referred to as the concentration-response relationship.

13. Conclusion:- For any toxic agent, contact with a biological membrane or system may not produce a measurable adverse effect if the concentration of the chemical is below a minimally effective(threshold) level. This principle also implies that all chemicals are capable of producing a deleterious effect if a high enough conc. Come into contact with a biological membrane or system.