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There's More to it at Hand
Glove effectiveness at reducing risk is built on the solid prerequisite of good and hygiene.
by Barry Michaels
Each of the barriers to transmission available to food safety managers (deli papers, utensils or gloves) have differing efficacies and limitations with respect to actual risk reduction. Proper use of utensils or gloves must be monitored and prevented from being used in ways that result in cross-contamination. Various types of gloves are employed in the food industry both to protect the food worker from occupational exposures related to food product or process, as well as to prevent pathogen or spoilage organism transmission from the worker to the product. The following is the first of a two-part article that reviews the type of gloves available to the food industry today and how to decide which type of glove should be used.
Effective Barrier Selection
A break must be instituted in the chain of transmission separating the worker and food contacted by that worker from the microflora associated with his or her existence and that of the home environment from which they came. To accomplish this separation, donning clean work clothing and obligatory pre-work hand hygiene is required, but it is frequently imperfect. Thus, additional barriers to the transmission must be put into place. If the task in question cannot be performed with bakery/deli papers or utensils, then choice of glove type and training associated with that selection is in order. There are now hundreds of different types of gloves available to food establishments according to material type, thickness, internal treatments (powder or otherwise), elasticity, exterior texturing and coatings. Glove selection is also dependent on allergy problems associated with natural latex in the medical field and the glove industry's response to finding suitable alternatives. Not all commercially available glove types have status allowing food contact. Medical grade gloves do not automatically translate for use in food establishments. FDA regulations recognize that various grades of gloves are available for use by food facilities and considers them to fall under the two main categories, multi-use and single-use gloves. Material durability, strength and cleanability are key factors in distinguishing these gloves. Multi-use gloves most often used in food processing are required to be durable, non-absorbent and resistant to corrosive sanitizers. At the same time they need to have sufficient strength to withstand repeated washing and sanitizing treatments without damage, distortion and/or decomposition. Table 1 lists the various types of gloves commonly used in the food industry. While the gloves discussed in these two articles will focus on those used in food preparation, gloves used as personal protective equipment (PPE) are also important components of successful facility operation. These gloves are used to protect workers from cuts, thermal and chemical injuries. Various materials or combinations thereof are available to perform these specific objectives. Most of these glove types are multi-use in nature and should be cleaned and sanitized on a regular basis to prevent potential cross-contamination within a food operation. Both multi-use and single-use gloves are required to meet composition requirements allowing contact with food. Regulations set forth in Title 21 of the Code of Federal Regulations (CFR) do not allow migration of deleterious substances, colors, odors or tastes to food. Under 110.10 (b) (5), they are required to be maintained in clean, intact and sanitary conditions. All gloves are considered items that will see repeat contact with food by both FDA and USDA and fall under the indirect food additive regulations described in 21 CFR 177.2600. Therefore, in order to verify FDA status under these regulations, a prolonged two-stage, elevated temperature chemical extraction using water and hexane solvents are required. This test data should be available from glove suppliers as a means of validating regulatory status. In any case, food contact status should be verified from supplier prior to purchase. If single use or disposable gloves are employed, they should be used for one purpose and must be discarded when soiled. They cannot and should not be reused under any circumstances. While numerous studies have shown excellent efficacy at cleaning gloves, generally being far more easily and effectively sanitized than the human hand, disposable gloves do not have the chemical and abrasive durability to make this a viable option. Facilities employing multi-use gloves can make use of cleaning and sanitizing regimens. Frequent washing and sanitizing steps that employ automatic or manual hygiene devices can quickly reinstate sanitary status without necessitating glove change. Used in this manner, these gloves take on the characteristics of a food handling utensil and are recognized as such in the FDA Food Code. Despite being more expensive initially, multi-use gloves can have overall low operational costs often being equivalent to disposable gloves. Here glove contamination is taken as a given and an SSOP is put into place to minimize that risk. Hands can only be washed or sanitized so much before skin damage ensues and there are limits on chemicals that can be utilized for fear of accelerating skin damage. In food processing, durable, sanitizer-resistant gloves can circumvent this limitation in both frequency and strength of antimicrobial compounds utilized. In this manner, cross-contamination involving Listeria monocytogenes, an ever-present concern for food processors, can be controlled within the plant.
When selecting gloves, it is important to include features such as break resistance, abrasive durability, resilience, elasticity, fit, tactile sensitivity and heat dissipation. Comfort or fit, seen as one of the most important factors when selecting hand protection, is derived from physical and mechanical properties inherent in each of the glove types. Figure 1 shows glove tensile strength plotted as a function of elongation at breaking point. This combines the two most important aspects of glove function in food handling environments. In this figure, tensile is measured in mega Pascal (M Pa) units, equivalent to 10.2 kg force per square centimeter. Data from five types of gloves are provided, except for polyethylene, in both new and aged condition. As can be seen from the data on the two polyethylene gloves, there is a great deal of variability with respect to strength characteristics of this glove type. The natural rubber latex glove is seen to be more susceptible to the effects of aging and oxidation. Although neoprene is not shown in this figure because of the huge variability found with this glove type. It, too, can also be affected by oxidation and exposure to elevated temperatures. For neoprene, latex and nitrile to counteract aging influences, various chemicals and antioxidants are added to glove materials during the manufacturing process. Polyurethane formulations have undergone formula changes since they were first introduced making them increasingly valuable to the food industry. In these newer formulations, elongation at break is comparable or superior to latex, making them generally much more comfortable to wear. Polyurethane materials such as Lycra can be made significantly thinner and lighter than comparable gloves and do not require additional chemical components to increase plasticity or stability. With the advantages of high tensile strength, durability and superior heat dissipation, polyurethane gloves are being used in applications where bulky neoprene or heavy duty latex gloves were previously utilized.
It is difficult to make specific recommendations as to where and how the various types of gloves should be used in the food environment because of the differing food types and handling configurations presented. Economics tend to dictate that unless there is a paradigm shift toward reuse, extremely short-term glove use would correspond to polyethylene (PE) or vinyl gloves while long term use as seen in food processing would insist on neoprene or polyurethane gloves with nitrile, and to a lesser extent, latex, used in intermediate situations. Ultimately, safety managers should match glove to worker and process effectiveness through in-use performance evaluations. Managers should know and understand the performance characteristics of the gloves being used relative to the specific hazards associated with food and process type. It is imperative to determine how long that glove can be worn by workers, while still remaining intact. What follows is a review of each of the major glove type available to the quality assurance manager. The second part of the article will make comparisons regarding physical attributes and aid food managers in choosing the right glove for the job. PE copolymer gloves are commonly utilized for short food handling tasks. They are loose fitting and due to sloppy fit, have less dexterity than that of either vinyl or natural rubber (NRL). While the loose fit allows venting of the hand, reducing moisture buildup within the glove, they tear quite easily and are not suitable for use around high heat. PE gloves are available in various densities which significantly influences the various physical properties. Melting can be a safety concern to users and safe working time is extremely limited. Based on testing of PE gloves for virus leakage, rates of around 50 percent leakage were seen for gloves in an unused state, whereas, after contact with ethanol, leakage increased to almost 100 percent. Compatibility with alcohol is clearly a problem and use of instant hand sanitizers just prior to donning could pose problems. Gloves of this material should be used for short duty tasks. The synthetic polymer in polyvinyl chloride (PVC) gloves replaces the protein matrix seen in natural latex with vinyl. They are considered by some to be an acceptable alternative to latex gloves, providing snug fit capabilities and dexterity. They are more resistant to ozone and oil than NRL and can be worn more safely around heat sources without the risk of melting. Unfortunately, testing has revealed, in some cases, that vinyl gloves begin leaking as soon as they are put on. Thin food service vinyl gloves have generally poor durability, lack of tensile strength and like PE, are susceptible to alcohol breakdown. They do however have better resistance to oils than NRL. However short wear times seriously limit their utility for food processing environments. Nitrile-butadiene rubber (NBR) is less elastic than NRL, has mechanical characteristics similar to vinyl in many respects, and is far more durable. Nitrile gloves are resistant to many chemicals but published data indicates sensitivity to alcohol degradation and generally poor flex properties in cold environments. NBR gloves come in a variety of colors, which can help in coding work areas. They have been found to be sensitive to ozone degradation and the elastomer can be somewhat brittle. While they are very resistant to abrasion, once punctured, they can sometimes tear with amazing ease. Nitrile gloves were designed to overcome allergen problems encountered with latex, however they have a number of the same chemical additives used in latex gloves, as well as additional additives that can potentially cause negative skin reactions. If upon changing to this glove type, similar skin problems are encountered in some individuals, it is a sign that the problem may involve antioxidants, accelerators or other potentially irritating sensitizing chemicals. NRL gloves have by far been considered the most comfortable of the tight-fitting glove types. Inexpensive, with good dexterity and tactile sensitivity, they have been valued for their physical properties until allergen problems surfaced in recent years. NRL gloves will deteriorate over time by exposure to oxygen, ozone or ultraviolet light and are degraded by fats, oils and solvents such as alcohol encountered in food environments. Deterioration of tensile properties can be seen in Figure 2 as a result of accelerated aging tests. Chloroprene rubber also known as polychloroprene, was conceived as a replacement for latex over 60 years ago and possesses unique chemical resistance characteristics not found in other glove types discussed until now. These gloves are commonly used for food processing tasks due to their lower allergen profile, good durability with oil, alcohol and chemical resistance. Gloves made from rubber conforming to the generic term neoprene are polymers or copolymers of chloroprene, similar to latex with respect to barrier properties and strength, although elasticity and comfort of fit sometimes suffers due to high modulus and stiffness. Neoprene may also contain other chemical additives similar to nitrile or latex necessary for the vulcanizing process. Like NRL, oxygen, ozone or UV light will deteriorate neoprene over time but to a much lesser extent. To overcome strength limitations, increases in thickness are employed. With high stiffness, this can be a factor in OSHA-related worker hand complaints. Dependent on the formulation and thickness, the tensile strengths of polychloroprene can be as high as 31 to 33 MPa topping all glove types with the exception of polyurethane. PU, other than the pure polymer itself, is chemically pure. Composed of polymeric methylene diphenyldiisocyanate, polyurethane formulations have come on to the glove scene off and on for many years undergoing formula changes making them increasingly appealing to the food industry. These glove types are head and shoulders above the rest with regard to having high tensile strength and durability (see Table. 2). Newer formulations have elongation at break comparable or superior to NRL, making them generally more comfortable to wear than earlier versions. They provide advantages of superior heat, oxidation and storage stability over latex, nitrile and neoprene. Because of their high tensile strengths, polyurethane materials such as Lycra can be made significantly thinner and lighter than comparable gloves. PU gloves are essentially semi-permeable membranes releasing moisture while at the same time maintaining superior barrier protection. They are resistant to abrasion, oils and depending on the formulation, are also resistant to alcohol deterioration. While slightly more expensive initially than other glove types, these gloves are extremely durable and offer the potential for reuse through in situ (on the hand) cleaning and sanitizing, not available to most other glove types other than neoprene. Each glove type possesses a unique set of advantages and disadvantages that set it apart from other glove types (see Table 2).
While no one glove type works for every food application, it goes without saying that as strength and durability increases, risk profile decreases. Studies taking place in food environments have shown that when gloves are worn beyond their capabilities, negative consequences can ensue. Upper management should address quality and safety problems before they occur, building resilience into the food safety/ quality system. To do so effectively requires flawed SSOPs involving gloves to be corrected. Glove effectiveness at reducing risk is built on the solid prerequisite of good hand hygiene. This means clean fingernails; if thin glove types are used, nails should be trimmed short (less that 2 mm) and smooth. Skin health is extremely important in glove selection. The hand really should be envisioned as a biofilm consisting of resident microbial species and specific characteristics that make it unlike all other skin surfaces. The hand cannot be sterilized, and even after repeated washings with disinfectant, will quickly repopulate. Normal flora has adapted to living on human body surfaces but when skin is damaged, as can occur due to chemicals commonly found in gloves or as a result of glove leaks, transient species can become colonizers. In addition to providing more information of making the right glove choice, the second part of this article will discuss new glove products and management systems that help reduce overall operational cost and provide that needed continuous process improvement. - FQ
Barry Michaels of B. Michaels Group Inc. can be reached at firstname.lastname@example.org.