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Local effects occur when the site of the damage is at the point of contact with the substance,
e.g. a corrosive burn on the skin.

Systemic effects occur when the site of damage is at a point other than the point of contact,
such as a target organ, e.g. the effect of inhaled lead fumes on the brain.

The Body Defence Mechanisms

The various functional systems have as their main function the maintenance of a healthy
body. The systems are constantly regulating conditions inside the body to balance the
activities of the person with the environmental conditions outside the body.

The response of the body to a variety of environmental conditions, sometimes called
‘environmental stresses’, will range from the harmless, such as sweating or coughing, to a
variety of diseases.

The body has two main categories of defence mechanism to combat attack by biological agents
and chemicals. Very broadly, these are:

Cellular defence (‘internal’ defence) – allows cells to fight bacteria and other toxins that have
entered mostly from blood, respiratory and ingestion routes.

Superficial defence (‘external’ defence) – protects against toxins that enter through the skin
and against the collection of contaminants that enter via the nose and throat by trapping them

in hairs and mucus.

POSHE V2| Unit IG2 – Element 7 – Chemical and Biological 12
Agents