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7.5 Specific Agents

Introduction

In this section, we consider number of toxic chemicals and biological agents and the hazards
which they pose, together with the circumstances in which the hazards arise. We also describe
the body reaction to entry of these agents, both in respect of the immediate superficial
response and the long-term body defence mechanisms.

There are several other commonly encountered chemical and biological agents that are
hazardous to health. These are described below, with an outline of the ill-health that they
cause and the relevant control measures.

Health Risks and Controls Associated with Other Specific Agents

Asbestos

Asbestos has been a widely used natural material which, although now banned in many
countries, is much in evidence in many workplaces. Previously used as an insulation and fire-
resistant material in building construction, it was also a common friction lining in machinery
(brakes, clutch plates, etc.).

The inhalation of asbestos fibres causes incurable respiratory diseases, mainly cancers of the
lung and chest lining. Death occurs only 15-60 years after exposure although the initial
symptoms (breathlessness and coughing) can appear sooner. Although the use of asbestos
is now banned in most countries, many people are still dying each year due to earlier
exposures and this number is still rising. Three main types of respiratory disease associated
with asbestos can be distinguished:

• Asbestosis is formation of scar tissue (fibrosis) in the walls of the alveoli (air sacs) causing
thickening and hence slowing the passage of oxygen into the blood, so causing
breathlessness on exertion.
• Mesothelioma is a type of cancer of the lining around the lungs and of the abdomen
(through swallowing asbestos fibres).
• Lung cancer occurs particularly amongst smokers exposed to asbestos. Fibres protecting
the lungs are flattened after inhaling cigarette smoke, so there is less protection against
asbestos fibres.
We still have the legacy of thousands of tonnes of asbestos in existing buildings. Some of it
is bound up in products such as asbestos cement and sprayed coatings. So long as it is in

ENSIGN| Unit IG2 – Element 7 – Chemical and Biological 49
Agents