As it will be explained in our next post; causes of chemical eye injuries, there are six main
groups of chemicals that damage the eyes and they include: organic solvents,
surfactants, irritants and allergens, aerosols, acids and alkali.
Organic solvents
Numerous substances of
this type are used in various industries but they rarely cause permanent
damage. Exposure to their vapour causes irritation and a more intense reaction
occurs if they are splashed into the eye as a liquid. They cause superficial
punctate keratitis of the cornea and conjunctiva. Some of the compounds are
caustic and may enter the stroma, denature the protein and produce scarring.
The subjective syptoms are pain, photophobia, lacrimation and stinging. Such
complaints are reported by those working with lacquers when solvents such as
alcohol, acetone, comphor, ether, toluene, benzol and acetates are used.
Examples of organic solvents and their uses in industries include the
following;
- Hydrocarbons (aliphatic and aromatic): used in dyeing, leather, rubber, linoleum, paints, varnish and lacquer industries; motor fuels.
- Halogenated hydrocarbons: solvents for fats, waxes, gums, resins, oils. Used in rubber and in paints, lacquers and varnishes; insecticides; antiseptics.
- Alcohols: solvents used in lacquers and polishes.
- Ketones: solvent in plastics, rubber, dyes and paint industries.
- Aldehyde: solvent for oils, resins, cellulose and are used in plastics and rubber industries.
- Ether: solvent in plastics manufacture.
- Ester: solvent in many industries; it is the least toxic organic solvent.
It is also important to
note that, when absorbed, these solvents have toxic effects that suppress the
central nervous system.
Surfactants
These compounds have a
fat-soluble group at one end of the molecule and water-soluble group at the
other end. This structure allows the compound to lower the surface tension of
water and to make fat-soluble materials miscible. They are used as industrial
detergents and as emulsifying agents and cause contact dermatitis and mucosal irritation.
Surfactants are divided into three main groups: cationic, anionic and
non-ionic.
Recommended: Acid and Alkali Chemical Eye Injury
The cationic group of surfactants
causes damage to the cornea and conjunctiva by precipitating the protein and if
severe enough, will lead to opacification of the corneal stroma, with
subsequent vascularization; quaternary ammonium compounds, such as benzylkonium
chloride, belong to this group. Anionic surfactants, such as soap, cause slow
saponification of intracellular lipoid substances and lysis of the cells.
Healing occurs quite quickly, leaving no permanent damage. The non-ionic
surfactants are usually esters of fatty acids with polyoxyethylene or sorbitol.
These do not cause any permanent damage as any corneal erosion produced heal
with no scarring
Irritants and allergens
Numerous substances may
irritate the eyes without causing permanent damage. A true allergy requires
sensitization of cells by prior exposure to an allergen. Subsequent exposure to
the allergen will then result in a typical allergic reaction. Common allergens
are organic substances of animal or vegetable origin, e.g. wool, pool and dairy
products. They produce the characteristic redness and swelling of tissues of
the lids and conjunctiva.
As new processes are
introduced into industry, the numbers of substances causing dermatitis and
conjunctivitis increase and many have not yet been isolated. Unfortunately the
appearance of the skin and conjunctiva often give no clue to the actual agent
involved.
It is possible to
desensitize people who are liable to attacks. In certain industries, allergic
skin reactions are well known and are recognized as industrial diseases.
Special trades may have easily identifiable irritants but there is no
explanation as yet for the fact that large numbers of people work for years with
common irritants, such as soap, without any ill effects.
Industries with a high
percentage of workers reporting dermatitis include baking, chemical
manufacturing, engineering, metal working, painting, preserving and textile
manufacturing. Adequate ventilation and protective goggles should be provided
where necessary to prevent dust and fumes contacting the eyes, as these may
cause serious secondary effects, such as purulent conjunctivitis and corneal
erosions.
Aerosols
Aerosols are commonly
used in households as well as industry. Their fine spray can cause a superficial
corneal inflammation, known as superficial punctate keratitis. After staining
with fluorescein these show up quite clearly as small punctate dots when seen
under ultraviolet (UV) light; these are temporary.
Photo Credit:
dominicanformula.com
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