TABLE OF CONTENTS 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. ?m-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.
For a classification of airborne contaminants, refer to Table 5.1
| Classification | Sub-groups | Examples |
|---|---|---|
| Irritants Have a corrosive or a vesicant (blistering) effect on moist or mucous surfaces. Concentration may be more important than duration of exposure. Animals and man react similarly. | ||
| Vapour, gases, mists | ||
| Upper respiratory | Acrolein; sulphur dioxide, hydrogen chloride, chromic acid; formaldehyde. |
| Upper and lower respiratory | Fluorine; chlorine; bromine; ozone; cyanogen chloride. | |
| Lower respiratory | Phosgene; nitrogen dioxide; arsenic trichloride. | |
| Skin | Inorganic acids (chromic, nitric); organic acids (acetic, butyric); inorganic alkalis (sodium hydroxide, sodium carbonate); organic bases (amines); organic... |
