Health and safety in the laboratory and field
Health and safety in the laboratory and field

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Health and safety in the laboratory and field

7 Hazards, risk and the process of risk assessment

7.1 Health problems associated with using chemicals

As described in Section 6.2, hazard is defined under COSHH as the inherently dangerous properties of a chemical or biological organism, and risk is defined as the likelihood of a chemical causing harm to people or to the environment.

There are several, more specific, known health problems associated with using chemicals. Advice on safety precautions when using a specific chemical are given in its associated safety phrase(s), which are described below.

7.1.1 Sensitising chemicals

Sensitising (Se) substances are known to cause allergic reactions in some people. These allergic reactions can be respiratory, and range from hayfever-like symptoms through to occupational asthma, for example, as caused by formaldehyde.

Other chemicals may cause skin allergies, which may lead to eczema, for example nickel and turpentine.

7.1.2 Carcinogenic chemicals

Several chemicals are known or suspected to cause cancer in humans and animals. These are known as carcinogenic (Ca) substances and under CHIP are divided into three categories:

  • categories 1 and 2 are defined as toxic, e.g. benzene;

  • category 3 is defined as harmful – this is often applied to chemicals that are suspected as being carcinogenic, e.g. dichloromethane.

7.1.3 Mutagenic chemicals

This is the term given to substances that are known to cause or are suspected of causing inherited changes. A mutagen is a substance that causes an increase in the rate of change in the genes (subsections of the DNA of the body's cells). These mutations can be passed along as the cell reproduces, sometimes leading to defective cells or cancer. Again there are three categories:

  • categories 1 and 2 are toxic, e.g. iodomethane;

  • category 3 is harmful, e.g. vanadium pentoxide.

7.1.4 Teratogenic chemicals

These chemicals are toxic to reproduction. A teratogen is an agent that can cause malformations of an embryo or a foetus. Once again there are three categories:

  • categories 1 and 2 are toxic, e.g. chromium trioxide;

  • category 3 is harmful, e.g. nandrolone (19-nortestosterone), a banned anabolic steroid.

If the substance is a category 1 or 2 carcinogen, mutagen or teratogen, all work must be carried out in a fume cupboard or equivalent. A category 3 carcinogen, mutagen, teratogen or sensitising substance is not so dangerous but it would be prudent to handle such a compound in a fume cupboard if one is available.


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