(introduction...)

How do hazardous agents get into the body?

If you look at a diagram of the human body you can see that it is exposed to the outside world through a variety of surfaces. These include the skin, lungs, nose, mouth and the digestive, urinary, and genital tracts. Hazardous agents (e.g. chemicals and micro-organisms such as bacteria and viruses) can get into the body through any of these surfaces. The most common routes of entry are:

(a) through the lungs (inhalation)
(b) through the skin (absorption)
(c) through the mouth (ingestion).