Module 4: Gloves - Types of Gloves

When to recommend gloves

The most important question to ask before recommending gloves is whether there is an exposure to a hazardous substance that would need their use. As will become apparent during this presentation, the use of gloves is a hazard and they should not be used lightly.

The type of exposure:

Having established that there is exposure or potential exposure to a hazardous substance, one must now establish the type of exposure. Unlike respiratory disease where only gaseous or aerosol products are considered, the skin can be exposed to all forms of a substance, from gas to a liquid to a solid. The form of exposure determines the potential for risk and thus also determines the need and choice of glove.

The type of exposure for which the gloves are needed to protect the worker must be established. Does the worker need protection from immersion in a hazardous substance as illustrated in (A)?

Is the worker to be protected while handling contaminated products as in (B)?

Are the gloves to be used as back-up splash protection alone (C)?

In each of these settings skin exposure varies.

The hazard environment:

Having established that there is a hazard and the type of exposure, the next thing to be considered before making a choice of glove is the hazard environment. A number of questions arise:

• What do I have to protect the worker from?
• Is the exposure to a pure, single substance?
• Does the final, end product represent a hazard and is it different from the raw products?
• Does the hazard change during the process being undertaken.
• Are intermediate substances produced representing a changing hazard environment in the process to be undertaken?

It is seldom that a worker is exposed only to a pure chemical but rather to mixtures of chemicals. There is little information on the risks and hazards of skin exposure to pure products and there is virtually no information on the risks and hazards of mixtures of substances.

The environmental conditions associated with the exposure can profoundly alter the hazard. These include temperature and humidity.

Substance concentration also alters the hazard and determines the type of reaction suspected. Exposure to dilute acid might cause sub-clinical damage where as exposure to concentrated acid a chemical burn.

The hazard environment:

Most skin hazards are not due to exposures to pure substances but to mixtures of substances. These occur under a variety of environmental conditions. Variations in temperature, humidity and substance concentration act as hazard modifiers with the hazard in gaseous, liquid or solid form. The choice of gloves must therefore protect the worker under a varying rather than specific set of conditions. Due consideration must be given to whether protection is for immersion, contaminated product handling or splash protection. Establishing these parameters is the easiest part of the decision making process into the choice of gloves.

Glove materials:

Gloves are made from a wide range of materials. The choice of material being dictated by the protection required. Materials include natural rubber latex, nitrile rubber, polychloroprene(neoprene), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), butyl rubber, fluorocarbon rubber, polyethylene and a variety of laminates.

In most work places gloves are issued to workers with little regard for the type of exposure and the type of work to be done. Originally gloves were designed for the medical profession to protect the patient from unnecessary exposure to infectious agents during operating procedures. Subsequently gloves have been used to protect the worker from exposure to noxious chemicals.

Each of the glove materials has advantages and disadvantages. Natural rubber latex is ideal for protection against water-miscible agents. Nitrile rubber should be chosen when the substance is an aromatic or aliphatic solvent. Neoprene is a substance of choice for strong acids. Because it is so inert PVC is used extensively in industry for rigid structures such as containers. However it is not a reliable glove material because of pinholes formed during the polymerisation process. Additional chemicals need to be incorporated into the polymer to make the material flexible and these interfere with the structural integrity. PVA, although excellent for chlorinated hydrocarbon, dissolves in water. Polyethylene gloves have reduced physical strength. Currently there is only one glove material, butyl rubber, that is acceptable for use with hydrogen fluoride. However it makes cumbersome gloves and their cost make them prohibitive for every day use. Similar problems are associated with fluorocarbon rubber gloves that are indicated for organic solvents such as toluene, xylene, trichloroethylene and PCB. All laminates have problems with pinholes and leaks especially along welds.

There is no single glove that can be used in every situation. Workers have to be supplied with a variety of gloves to meet each exposure situation requirements.

Natural rubber latex has a low modulus. Gloves made from it are strong and extremely flexible, allowing good hand movement and dexterity with some preservation of sensory perception. Nitrile rubber has a higher modulus and gloves made from it are more easily torn and more cumbersome. This and the cost limit its popularity for general use. Neoprene rubber, although having a low modulus and thus providing a strong, flexible material for glove manufacture, has a slippery surface, limiting its general use. Polyethylene, which has numerous uses in industry, has poor physical strength when used for gloves and they are not reliable except for short-term splash protection. Butyl rubber and fluorocarbon rubbers are weak rubbers. Gloves made from them are cumbersome and very expensive. Fluorocarbon rubber is difficult to dispose of and hence has environmental implications in its use.

The EU glove coding system:

The European Union has devised a coding system for manufacturers to use on gloves to provide guidance for industrial marketing choice. While these are exceptionally good for physical and mechanical hazards, the chemical protection ratings are not extensive enough as yet.