The legal definition of substances hazardous to health is any substance or mixture of substance which: ● Displays a very toxic, toxic, corrosive, harmful or irritant hazard symbol on the label ● Has an exposure limit approved by the Health and Safety Executive ● Is a biological agent ● Is any dust at a substantial concentration in the air ● Is not mentioned above but creates a health hazard comparable to any of them Different Forms Hazardous substances come in many forms including: ● Liquids (e.g. cleaning chemicals) ● Dust (e.g. lead and asbestos) ● Fumes ● Gases (e.g. carbon monoxide) ● Living organisms (e.g. bodily fluids) Routes of Entry Hazardous substances can get into our bodies through different routes, and each combination of substance and route has its own dangers and symptoms. Different routes of entry are as follows: ● Inhalation: Through breathing in hazardous substances, such as toxic fumes ● Ingestion: Through swallowing a hazardous substance or where one might be splashed into the mouth ● Eyes: Substances can irritate the eyes either directly, by splashes, dust or fumes entering the eyes, or indirectly by people handling hazardous substances and then rubbing their eyes ● Absorption: Where a hazardous substance gets onto the skin and is absorbed through the skin into the body and the bloodstream. Skin can prevent most hazardous substances from passing through, but not all. Absorption is normally associated with dermatitis when the skin comes into contact with strong acids, alkalis and solvents ● Injection: Where a sharp object, such as a needle has a hazardous substance on it and cuts or punctures the skin. Defences Against Entry Our bodies have many natural defences against dangerous substances, such as the following: ● Skin ● The lining of gut and airways ● Coughing ● Sneezing ● Diarrhoea ● Vomiting