Hazards

There are several general categories of bodily hazards for which specialized clothing can provide protection. These general categories include chemical, physical and biological hazards. Table 1 summarizes these.

Table 1. Examples of dermal hazard categories

Chemical hazards

Protective clothing is a commonly used control to reduce worker exposures to potentially toxic or hazardous chemicals when other controls are not feasible. Many chemicals pose more than one hazard (for example, a substance such as benzene is both toxic and flammable). For chemical hazards, there are at least three key considerations that need attention. These are (1) the potential toxic effects of exposure, (2) likely routes of entry, and (3) the exposure potentials associated with the work assignment. Of the three aspects, toxicity of the material is the most important. Some substances simply present a cleanliness problem (e.g., oil and grease) while other chemicals (e.g., contact with liquid hydrogen cyanide) could present a situation which is immediately dangerous to life and health (IDLH). Specifically, the toxicity or hazardousness of the substance by the dermal route of entry is the critical factor. Other adverse effects of skin contact, besides toxicity, include corrosion, promotion of cancer of the skin and physical trauma such as burns and cuts.

An example of a chemical whose toxicity is greatest by the dermal route is nicotine, which has excellent skin permeability but is not generally an inhalation hazard (except when self-administered). This is only one of many instances where the dermal route offers a much more significant hazard than the other routes of entry. As suggested above, there are many substances that are not generally toxic but are hazardous to the skin because of their corrosive nature or other properties. In fact, some chemicals and materials can offer an even greater acute risk through skin absorption than the most dreaded systemic carcinogens. For example, a single unprotected skin exposure to hydrofluoric acid (above 70% concentration) can be fatal. In this case, as little as a 5% surface burn typically results in death from the effects of the fluoride ion. Another example of a dermal hazard—though not an acute one—is the promotion of skin cancer by substances such as coal tars. An example of a material which has high human toxicity but little skin toxicity is inorganic lead. In this case the concern is contamination of the body or clothing, which could later lead to ingestion or inhalation, since the solid will not permeate intact skin.

Once an evaluation of the routes of entry and toxicity of the materials has been completed, an assessment of the likelihood of exposure needs to be carried out. For example, do workers have enough contact with a given chemical to become visibly wet or is exposure unlikely and protective clothing intended to act simply as a redundant control measure? For situations where the material is deadly although the likelihood of contact is remote, the worker must obviously be provided with the highest level of protection available. For situations where the exposure itself represents a very minimal risk (e.g., a nurse handling 20% isopropyl alcohol in water), the level of protection does not need to be fail-safe. This selection logic is essentially based on an estimate of the adverse effects of the material combined with an estimate of the likelihood of exposure.

The chemical resistance properties of barriers

Research showing the diffusion of solvents and other chemicals through “liquid-proof” protective clothing barriers has been published from the 1980s to the 1990s. For example, in a standard research test, acetone is applied to neoprene rubber (of typical glove thickness). After direct acetone contact on the normal outside surface, the solvent can normally be detected on the inside surface (the skin side) within 30 minutes, although in small quantities. This movement of a chemical through a protective clothing barrier is called permeation. The permeation process consists of the diffusion of chemicals on a molecular level through the protective clothing. Permeation occurs in three steps: absorption of the chemical at the barrier surface, diffusion through the barrier, and desorption of the chemical on the normal inside surface of the barrier. The time elapsed from the initial contact of the chemical on the outside surface until detection on the inside surface is called the breakthrough time. The permeation rate is the steady-state rate of movement of the chemical through the barrier after equilibrium is reached.

Most current testing of permeation resistance extends over periods of up to eight hours, reflecting normal work shifts. However, these tests are conducted under conditions of direct liquid or gaseous contact that typically do not exist in the work environment. Some would therefore argue that there is a significant “safety factor” built into the test. Countering this assumption are the facts that the permeation test is static while the work environment is dynamic (involving flexing of materials or pressures generated from gripping or other movement) and that there may exist prior physical damage to the glove or garment. Given the lack of published skin permeability and dermal toxicity data, the approach taken by most safety and health professionals is to select the barrier with no breakthrough for the duration of the job or task (usually eight hours), which is essentially a no-dose concept. This is an appropriately conservative approach; however, it is important to note that there is no protective barrier currently available which provides permeation resistance to all chemicals. For situations where the breakthrough times are short, the safety and health professional should select the barriers with the best performance (i.e., with the lowest permeation rate) while considering other control and maintenance measures as well (such as the need for regular clothing changes).

Aside from the permeation process just described, there are two other chemical resistance properties of concern to the safety and health professional. These are degradation and penetration. Degradation is a deleterious change in one or more of the physical properties of a protective material caused by contact with a chemical. For example, the polymer polyvinyl alcohol (PVA) is a very good barrier to most organic solvents, but is degraded by water. Latex rubber, which is widely used for medical gloves, is of course water resistant, but is readily soluble in such solvents as toluene and hexane: it would be plainly ineffective for protection against these chemicals. Secondly, latex allergies can cause severe reactions in some people.

Penetration is the flow of a chemical through pinholes, cuts or other imperfections in protective clothing on a nonmolecular level. Even the best protective barriers will be rendered ineffective if punctured or torn. Penetration protection is important when the exposure is unlikely or infrequent and the toxicity or hazard is minimal. Penetration is usually a concern for garments used in splash protection.

Several guides have been published listing chemical resistance data (many are also available in an electronic format). In addition to these guides, most manufacturers in the industrially developed countries also publish current chemical and physical resistance data for their products.

Physical hazards

As noted in table 1, physical hazards include thermal conditions, vibration, radiation and trauma as all having the potential to affect the skin adversely. Thermal hazards include the adverse effects of extreme cold and heat on the skin. The protective attributes of clothing with respect to these hazards is related to its degree of insulation, whereas protective clothing for flash fire and electric flashover requires flame resistance properties.

Specialized clothing can provide limited protection from some forms of both ionizing and non-ionizing radiation. In general, the effectiveness of clothing that protects against ionizing radiation is based on the principle of shielding (as with lead-lined aprons and gloves), whereas clothing employed against non-ionizing radiation, such as microwave, is based on grounding or isolation. Excessive vibration can have several adverse effects on body parts, primarily the hands. Mining (involving hand-held drills) and road repair (for which pneumatic hammers or chisels are used), for example, are occupations where excessive hand vibration can lead to bone degeneration and loss of circulation in the hands. Trauma to the skin from physical hazards (cuts, abrasions, etc.) is common to many occupations, with construction and meat cutting as two examples. Specialized clothing (including gloves) are now available which are cut-resistant and are used in applications such as meat cutting and forestry (using chain saws). These are based either on inherent cut-resistance or the presence of enough fibre mass to clog moving parts (e.g., chain saws).

Biological hazards

Biological hazards include infection due to agents and disease common to humans and animals, and the work environment. Biological hazards common to humans have received great attention with the increasing spread of blood-borne AIDS and hepatitis. Hence, occupations which might involve exposure to blood or body fluids usually require some type of liquid-resistant garment and gloves. Diseases transmitted from animals through handling (e.g., anthrax) have a long history of recognition and require protective measures similar to those used for handling the kind of blood-borne pathogens that affect humans. Work environments that can present a hazard due to biological agents include clinical and microbiological laboratories as well as other special work environments.

Types of Protection

Protective clothing in a generic sense includes all elements of a protective ensemble (e.g., garments, gloves and boots). Thus, protective clothing can include everything from a finger cot providing protection against paper cuts to a fully encapsulating suit with a self-contained breathing apparatus used for an emergency response to a hazardous chemical spill.

Protective clothing can be made of natural materials (e.g., cotton, wool and leather), man-made fibres (e.g., nylon) or various polymers (e.g., plastics and rubbers such as butyl rubber, polyvinyl chloride, and chlorinated polyethylene). Materials which are woven, stitched or are otherwise porous (not resistant to liquid penetration or permeation) should not be used in situations where protection against a liquid or gas is required. Specially treated or inherently non-flammable porous fabrics and materials are commonly used for flash fire and electric arc (flashover) protection (e.g., in the petrochemical industry) but usually do not provide protection from any regular heat exposure. It should be noted here that fire-fighting requires specialized clothing that provides flame (burning) resistance, a water barrier and thermal insulation (protection from high temperatures). Some special applications also require infrared (IR) protection by use of aluminized overcovers (e.g., fighting petroleum fuel fires). Table 2 summarizes typical physical, chemical, and biological performance requirements and common protective materials used for hazard protection.

Table 2. Common physical, chemical and biological performance requirements

Protective clothing configurations vary greatly depending on the intended use. However, normal components are analogous to personal clothing (i.e., trousers, jacket, hood, boots and gloves) for most physical hazards. Special-use items for applications such as flame resistance in those industries involving the processing of molten metals can include chaps, armlets, and aprons constructed of both treated and untreated natural and synthetic fibres and materials (one historical example would be woven asbestos). Chemical protective clothing can be more specialized in terms of construction, as shown in figure 1 and figure 2.

Figure 1. A worker wearing gloves and a chemically protective garment pouring chemical

Figure 2. Two workers in differing configurations of chemical protective clothing

Chemically protective gloves are usually available in a wide variety of polymers and combinations; some cotton gloves, for example, are coated by the polymer of interest (by means of a dipping process). (See figure 3). Some of the new foil and multilaminate “gloves” are only two-dimensional (flat)—and hence have some ergonomic constraints, but are highly chemical resistant. These gloves typically work best when a form-fitting outer polymer glove is worn over the top of the inner flat glove (this technique is called double gloving) to conform the inner glove to the shape of the hands. Polymer gloves are available in a wide variety of thicknesses ranging from very light weight (<2 mm) to heavy weight (>5 mm) with and without inner liners or substrates (called scrims). Gloves are also commonly available in a variety of lengths ranging from approximately 30 centimetres for hand protection to gauntlets of approximately 80 centimetres, extending from the worker’s shoulder to the tip of the hand. The correct choice of length depends on the extent of protection required; however, the length should normally be sufficient to extend at least to the worker’s wrists so as to prevent drainage into the glove. (See figure 4).

Figure 3. Various types of chemically resistant gloves

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Figure 4. Natural-fibre gloves; also illustrates sufficient length for wrist protection

Boots are available in a wide variety of lengths ranging from hip length to those that cover only the bottom of the foot. Chemical protective boots are available in only a limited number of polymers since they require a high degree of abrasion resistance. Common polymers and rubbers used in chemically resistant boot construction include PVC, butyl rubber and neoprene rubber. Specially constructed laminated boots using other polymers can also be obtained but are quite expensive and in limited supply internationally at the present time.

Chemical protective garments can be obtained as a one-piece fully encapsulating (gas-tight) garment with attached gloves and boots or as multiple components (e.g., trousers, jacket, hoods, etc.). Some protective materials used for construction of ensembles will have multiple layers or laminas. Layered materials are generally required for polymers that do not have good enough inherent physical integrity and abrasion resistance properties to permit manufacture and use as a garment or glove (e.g., butyl rubber versus Teflon®). Common support fabrics are nylon, polyester, aramides and fibreglass. These substrates are coated or laminated by polymers such as polyvinyl chloride (PVC), Teflon®, polyurethane and polyethylene.

Over the last decade there has been an enormous growth in the use of nonwoven polyethene and microporous materials for disposable suit construction. These spun-bonded suits, sometimes incorrectly called “paper suits,” are made using a special process whereby the fibres are bonded together rather than woven. These protective garments are low in cost and very light in weight. Uncoated microporous materials (called “breathable” because they allow some water vapour transmission and hence are less heat stressful) and spun-bonded garments have good applications as protection against particulates but are not normally chemical-or liquid-resistant. Spun-bonded garments are also available with various coatings such as polyethylene and Saranex®. Depending on the coating characteristics, these garments can offer good chemical resistance to most common substances.

Approval, Certification and Standards

The availability, construction, and design of protective clothing varies greatly throughout the world. As might be expected, approval schemes, standards and certifications also vary. Nevertheless, there are similar voluntary standards for performance throughout the United States (e.g., American Society for Testing and Materials—ASTM—standards), Europe (European Committee for Standardization—CEN—standards), and for some parts of Asia (local standards such as in Japan). The development of worldwide performance standards has begun through the International Organization for Standardization Technical Committee 94 for Personal Safety-Protective Clothing and Equipment. Many of the standards and test methods to measure performance developed by this group were based on either CEN standards or those from other countries such as the United States through the ASTM.

In the United States, Mexico, and most of Canada, no certification or approvals are required for most protective clothing. Exceptions exist for special applications such as pesticide applicators clothing (governed by pesticide labelling requirements). Nevertheless, there are many organizations that issue voluntary standards, such as the previously mentioned ASTM, the National Fire Protection Association (NFPA) in the United States and the Canadian Standards Organization (CSO) in Canada. These voluntary standards do significantly affect the marketing and sale of protective clothing and hence act much like mandated standards.

In Europe, the manufacturing of personal protective equipment is regulated under the European Community Directive 89/686/EEC. This directive both defines which products fall within the scope of the directive and classifies them into different categories. For categories of protective equipment where the risk is not minimal and where the user cannot readily identify the hazard easily, the protective equipment must meet standards of quality and manufacture detailed in the directive.

No protective equipment products may be sold within the European Community unless they have the CE (European Community) mark. Testing and quality assurance requirements must be followed to receive the CE mark.

Individual Capabilities and Needs

In all but a few cases, the addition of protective clothing and equipment will decrease productivity and increase worker discomfort. It may also lead to decreased quality, since error rates increase with the use of protective clothing. For chemical protective and some fire-resistant clothing there are some general guidelines that need to be considered concerning the inherent conflicts between worker comfort, efficiency and protection. First, the thicker the barrier the better (increases the time to breakthrough or provides greater thermal insulation); however, the thicker the barrier the more it will decrease ease of movement and user comfort. Thicker barriers also increase the potential for heat stress. Second, barriers which have excellent chemical resistance tend to increase the level of worker discomfort and heat stress because the barrier normally will also act as a barrier to water vapour transmission (i.e., perspiration). Third, the higher the overall protection of the clothing, the more time a given task will take to accomplish and the greater the chance of errors. There are also a few tasks where the use of protective clothing could increase certain classes of risk (e.g., around moving machinery, where the risk of heat stress is greater than the chemical hazard). While this situation is rare, it must be considered.

Other issues relate to the physical limitations imposed by using protective clothing. For example, a worker issued a thick pair of gloves will not be able to perform tasks easily that require a high degree of dexterity and repetitive motions. As another example, a spray painter in a totally encapsulating suit will usually not be able to look to the side, up or down, since typically the respirator and suit visor restrict the field of vision in these suit configurations. These are only some examples of the ergonomic restrictions associated with wearing protective clothing and equipment.

The work situation must always be considered in the selection of the protective clothing for the job. The optimum solution is to select the minimum level of protective clothing and equipment that is necessary to do the job safely.

Education and Training

Adequate education and training for users of protective clothing is essential. Training and education should include:

• the nature and extent of the hazards

• the conditions under which protective clothing should be worn

• what protective clothing is necessary

• the use and limitations of the protective clothing to be assigned

• how to inspect, don, doff, adjust and wear the protective clothing properly

• decontamination procedures, if necessary

• signs and symptoms of overexposure or clothing failure

• first aid and emergency procedures

• the proper storage, useful life, care and disposal of protective clothing.

This training should incorporate at least all of the elements listed above and any other pertinent information that has not already been provided to the worker through other programmes. For those topical areas already provided to the worker, a refresher summary should still be provided for the clothing user. For example, if the signs and symptoms of overexposure have already been indicated to the workers as part of their training for working with chemicals, symptoms that are a result of significant dermal exposures versus inhalation should be reemphasized. Finally, the workers should have an opportunity to try out the protective clothing for a particular job before a final selection is made.

Knowledge of the hazard and of the limitations of the protective clothing not only reduces the risk to the worker but also provides the health and safety professional with a worker capable of providing feedback on the effectiveness of the protective equipment.

Maintenance

The proper storage, inspection, cleaning and repair of protective clothing is important to the overall protection provided by the products to the wearer.

Some protective clothing will have storage limitations such as a prescribed shelf life or required protection from UV radiation (e.g., sunlight, welding flash, etc.), ozone, moisture, temperature extremes or prevention of product folding. For example, natural rubber products usually call for all of the precautionary measures just listed. As another example, many of the encapsulating polymer suits can be damaged if folded rather than allowed to hang upright. The manufacturer or distributor should be consulted for any storage limitations their products may have.

Inspection of protective clothing should be performed by the user on a frequent basis (e.g., with each use). Inspection by co-workers is another technique which may be used to involve wearers in ensuring the integrity of the protective clothing they have to use. As a management policy, it is also advisable to require supervisors to inspect protective clothing (at appropriate intervals) that is used on a routine basis. Inspection criteria will depend on the intended use of the protective item; however, it would normally include examination for tears, holes, imperfections and degradation. As one example of an inspection technique, polymer gloves used for protection against liquids should be blown up with air to check for integrity against leaks.

Cleaning of protective clothing for reuse must be performed with care. Natural fabrics can be cleaned by normal washing methods if they are not contaminated with toxic materials. Cleaning procedures suitable for synthetic fibres and materials are commonly limited. For example, some products treated for flame resistance will lose their effectiveness if not properly cleaned. Clothing used for protection against chemicals which are not water-soluble often cannot be decontaminated by washing with simple soap or detergent and water. Tests performed on pesticide applicators’ clothing indicate that normal washing procedures are not effective for many pesticides. Dry cleaning is not recommended at all since it is often ineffective and can degrade or contaminate the product. It is important to consult the manufacturer or distributor of the clothing before attempting cleaning procedures that are not specifically known to be safe and workable.

Most protective clothing is not repairable. Repairs can be made on some few items such as fully encapsulating polymer suits. However, the manufacturer should be consulted for the proper repair procedures.

Use and Misuse

Use. First and foremost, the selection and proper use of protective clothing should be based on an assessment of the hazards involved in the task for which the protection is required. In light of the assessment, an accurate definition of the performance requirements and the ergonomic constraints of the job can be determined. Finally, a selection that balances worker protection, ease of use and cost can be made.

A more formal approach would be to develop a written model programme, a method that would reduce the chance of error, increase worker protection and establish a consistent approach to the selection and use of protective clothing. A model programme could contain the following elements:

1. an organization scheme and administrative plan
2. a risk assessment methodology
3. an evaluation of other control options to protect the worker
4. performance criteria for the protective clothing
5. selection criteria and procedures to determine the optimum choice
6. purchasing specifications for the protective clothing
7. a validation plan for the selection made
8. decontamination and reuse criteria, as applicable
9. a user training programme
10. 10.an auditing plan to assure that procedures are consistently followed.

Misuse. There are several examples of misuse of protective clothing that can commonly be seen in industry. Misuse is usually the result of a lack of understanding of the limitations of protective clothing on the part of management, of the workers, or of both. A clear example of bad practice is the use of nonflame-resistant protective clothing for workers who handle flammable solvents or who work in situations where open flames, burning coals or molten metals are present. Protective clothing made of polymeric materials such as polyethylene may support combustion and can actually melt into the skin, causing an even more severe burn.

A second common example is the reuse of protective clothing (including gloves) where the chemical has contaminated the inside of the protective clothing so that the worker increases his or her exposure on each subsequent use. One frequently sees another variation of this problem when workers use natural-fibre gloves (e.g., leather or cotton) or their own personal shoes to work with liquid chemicals. If chemicals are spilled on the natural fibres, they will be retained for long periods of time and migrate to the skin itself. Yet another variation of this problem is taking contaminated work clothing home for cleaning. This can result in the exposure of an entire family to harmful chemicals, a common problem because the work clothing is usually cleaned with the other articles of clothing of the family. Since many chemicals are not water-soluble, they can be spread to other articles of clothing simply by mechanical action. Several cases of this spread of contaminants have been noted, especially in industries which manufacture pesticides or process heavy metals (e.g., poisoning families of workers handling mercury and lead). These are only a few of the more prominent examples of the misuse of protective clothing. These problems can be overcome by simply understanding the proper use and limitations of the protective clothing. This information should be readily available from the manufacturer and health and safety experts.

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