1. Chemical Agents Routes of Entry and the Body’s Defences

2. Routes of Entry l Skin contact l Inhalation l Ingestion l Injection

3. Inhalation l The lung is the most vulnerable part of the body l Even small concentrations of a toxic agent in the atmosphere being inhaled can, after a period, develop a build-up of toxicant in the body

4. Skin Contact l Has many layers of protection and does not allow solid or gaseous substances to be absorbed, so only liquids provide a hazard l Skin of hands, arms & legs usually has some breaks in its surface, do risk of entry by injection is a possibility

5. Ingestion l Gastrointestinal tract is least vulnerable area of the body l Possibility of solid or liquid toxicants being ingested is very limited

6. Local Effects l Confined to specific area of body where contact with the toxic material occurs l For example, a sensitiser may cause a specific allergic reaction on contact with the skin or respiratory tract

7. Systemic Effects l Occur at organs/parts of the body distant from the site where initial contact with the toxic substance was made l Common target organs include lungs, liver, nervous system, bone marrow, kidneys and skin

8. Defence Mechanisms of the Body l Respiratory Defence l Lachrymation l Immune Response l Inflammatory Response l Fibrotic Response

9. Respiratory Defence l Moist hairs in the nose trap large particles l Other particles are sneezed or coughed out l Very tiny particles are breathed in and back out again l Solid deposits in the lower respiratory airway are moved up the ciliary escalator l 0.5 - 7 microns is the respirable range

10. Respiratory Protection l Phagocytosis Amoeba like cells which engulf particles of dust and remove them Can cause formation of elastic scar tissue on lungs for certain dusts, which leads to reduced lung function

11. Lachrymation l Eye is protected from injury by bony structure which houses it l Eyebrows divert liquids to outer side l Eyelashes prevent particles from entering eyes and cause lids to close rapidly if touched l Exposed surface of eye is continuously moistened by tears (lachrymation) - any irritation of the eye causes an immediate increase in secretion and the irritation is diluted or washed away

12. Immune Response l Rash occurs on skin in response to contact with certain substances l Once sensitisation occurs, further exposure to the substance even at low concentrations will cause inflammation

13. Inflammatory Response l The reaction of tissue to a harmful agent which is insufficient to kill the tissue l A defensive process, but can result in disease if called upon to act for too long l Collagen is formed to repair damaged tissue