Chemicals may be encountered as reactants, solvents, catalysts, inhibitors, as starting materials,
finished products, by-products, contaminants, or off-specification products. They may vary from
pure, single substances to complex proprietary formulations.
Exposures to chemicals may involve solids, liquids, or airborne matter as mists, aerosols,
dusts, fumes (i.e. µm-sized particulates), vapours or gases in any combination. Many situations,
e.g. exposure to ....
Chemicals may be encountered as reactants, solvents, catalysts, inhibitors, as starting materials,
finished products, by-products, contaminants, or off-specification products. They may vary from
pure, single substances to complex proprietary formulations.
Exposures to chemicals may involve solids, liquids, or airborne matter as mists, aerosols,
dusts, fumes (i.e. µm-sized particulates), vapours or gases in any combination. Many situations,
e.g. exposure to welding fumes or to combustion products from fossil fuels, include mixtures both
of chemicals and of physical forms. Quantification of exposure is then difficult.
An exposure to a specific chemical in relatively low concentrations over a period may result
in chronic effects. At higher concentrations, the effects may be acute. Some chemicals produce
local damage at their point of contact with, or entry into, the body; others produce systemic
effects, i.e. they are transported within the body to various organs before exerting an adverse
effect.
The toxicity of a substance is its capacity to cause injury once inside the body. The main modes
of entry into the body by chemicals in industry are inhalation, ingestion and absorption through
the skin. Gases, vapours, mists, dusts, fumes and aerosols can be inhaled and they can also affect
the skin, eyes and mucous membranes. Ingestion is rare although possible as a result of poor
personal hygiene, subconscious hand-to-mouth contact, or accidents. The skin can be affected
directly by contact with the chemicals, even when intact, but its permeability to certain substances
also offers a route into the body.