A. Inhalation

More hazardous agents get into your body by inhalation (by being breathed in) than by any other route.

Your respiratory system filters the air you breathe

Your body's respiratory system has very effective mechanisms for filtering out normal pollutants from the air you breathe. Filtering systems in the nose and mouth (for example, the hairs in the nose, the mucus in the mouth and lungs) prevent large foreign particles (like coarse dust) from travelling down into your lungs where they can have damaging effects. The hairs in your nose trap large dust particles. You can see how effective this natural filter is by blowing your nose after working in a dusty or smoke-filled environment.

Can particles get past these filtering mechanisms?

Generally, large dust particles (including fibres) can be filtered out of the respiratory system. But small dust particles are difficult to eliminate and can reach the deepest parts of the lungs where they can cause serious local respiratory problems. (See section III of this Module for an explanation of local effects.)

When the lungs are exposed to high concentrations of dust, toxic vapours, cigarette smoke, etc. (high amounts of the pollutant in the air), the filtering mechanisms can become overloaded and damaged. Once they are damaged, various bacteria, viruses, etc. are more likely to grow in the lungs, causing infections such as pneumonia. That is why workers in dusty occupations (bauxite and coalminers, sugar factory and asbestos workers, flour mill workers, furniture makers, etc.) are known to be more susceptible (open) to tuberculosis, bronchitis and other respiratory diseases than workers in non-dusty occupations.

Can other forms of chemicals be inhaled as well?

Other forms of chemicals can also enter the body through the respiratory system. Chemicals come in a range of forms: vapours, solids, liquids, dusts, gases (see the Module, Chemicals in the workplace for an explanation of each of these chemical forms) and you can inhale almost all of these. Some chemicals will have damaging local effects on the lungs, while others will be absorbed into the bloodstream and have potentially damaging effects on various target organs.

Target organs are those parts of the body that particular chemicals always affect. For example, lead affects the central nervous system (brain and spinal cord) but is stored in the bones where it accumulates (increases) with further exposures. Therefore, the target organs for lead are both the central nervous system and the bones. Other target organs for different chemicals are the heart, lungs, kidneys and liver.

How do you know whether you are being exposed to respiratory hazards at work?

Your body has several built-in mechanisms which can act as warning signals when hazards are present:

· smell · sneezing · coughing · a runny nose

These physical responses, or signals, will sometimes tell you there is a potential hazard present. In some cases these also will help you to remove a hazardous agent from your respiratory system. However, sometimes these signals will not warn you about hazards. For example, some chemicals have no odour so you cannot smell them. There are other chemicals that you can only smell when the concentration is well above so-called “safe levels” and already harming your health, and there are certain chemicals that you cannot smell after being around them for a while - your nose gets “accustomed” or used to them. Therefore, smell is not always a reliable warning signal.

New workers and visitors are another potential signal to workplace hazards. They are “newly exposed” and can tell you if they have health problems only when they come into the workplace.