A latex glove alert!

Think twice before reaching for natural rubber PPE

Miriam C. Nagel

There are two things the user should be aware of before putting on a natural rubber latex glove, particularly a disposable glove. First, the barrier protective capability may not be adequate for the chemical hazard. Second, repeated exposure to natural rubber latex gloves may lead to allergic reactions such as skin rashes, hives, nasal, eye, or sinus symptoms even asthma, and, in rare cases, shock. Once a user is sensitized to latex in gloves, any latex can trigger a reaction in or out of the laboratory. The risk for the unlucky victim of latex allergy can be so severe that the National Institute for Occupational Safety and Health (NIOSH) recommends that the latex allergic person wear a medical alert bracelet (1)

Fatal failure of a disposable latex glove
The possibility of a chemical passing through a disposable latex glove is tragically illustrated by the June 8, 1997 death of Dartmouth College chemistry professor, Karen E. Wetterhahn. In a letter to Chemical & Engineering News shortly before Dr. Wetterhahn's death, Michael B. Blayney, director of environmental health and safety at Dartmouth, and two other Dartmouth authors, said her severe mercury toxicity was the result of "a single exposure to dimethylmercury.

"Review of research notes, interviews, hair analysis, and statements made by the patient established the circumstances and events described here. Testing of the type of gloves worn by the patient supports the hypothesis that dimethylmercury rapidly penetrated them, resulting in transdermal exposure.

"It appears that there was only one acute exposure to dimethylmercury. The patient recounted spilling one or several drops (estimated to total 0.1 to 0.5 mL) on disposable latex gloves during a transfer procedure in a fume hood while preparing a mercury nuclear magnetic resonance standard" (2).

Blayney said in an interview that there were seven brands of thin-latex or PVC disposable medical type gloves used in the Dartmouth laboratories. All types were tested by Inchcape Testing Services of Cortland, NY. Using ASTM (American Society for Testing and Materials) methodology, the lab established "maximum permeation at 15 seconds, the quickest time they could sample" (3). In effect, Dr. Wetterhahn didn't have any protection from the disposable latex gloves.

TO SIDEBAR: Products containing latex

How does a chemist know which glove to use?
Blayney says there is no simple answer. For example, emergency response workers who have no time to seek an evaluation of the risk and may not know what chemicals or combinations are present at a scene may use Silver Shield (trademark of North Hand Protection), or similar laminated gloves, in combination with a neoprene or nitrile glove. But such a combination of gloves may not provide the dexterity needed in research such as Dr. Wetterhahn was doing. It is a tough problem.

Lab Safety Supply, Inc., a commercial supplier that provides a Safety TechLine and EZ Facts Safety Information, claims that Silver Shield protective wear offers "the highest level of overall chemical resistance, but has virtually no cut resistance" (4). That is why something like a nitrile glove that is cut-resistant is worn over the laminated glove.

But caution! "Overall chemical resistance" may not include the particular hazardous chemical or combination of chemicals to be used. Standard test data available from glove manufacturers are generally only for pure chemicals. Combinations of chemicals, particularly high-risk chemicals, require specific tests on the glove or glove combination of choice using accepted ASTM methods, as Blayney did in researching the cause of the fatal incident at Dartmouth.

Blayney reports that in response to Professor Wetterhahn's death, Dartmouth has taken several steps to help ensure that scientists are better informed about how to select the best glove for the application. A brightly colored label is attached to every box of disposable latex and PVC gloves sold through the college stockrooms warning researchers that such gloves are "not suitable for use with hazardous materials." The college has sponsored glove safety workshops and prominently displayed colored posters with glove safety information. (see sidebar: Essential Information on the Selection and Use..., below).

TO SIDEBAR: Essential Information on the Selection and Use...

Sources of information
The glove manufacturers make information about glove tests and test data readily available to the public. Best Manufacturing Company (Menlo, GA) publishes the Guide to Chemical- Resistant Best Gloves (5). The guide has been reviewed by Jeffrey O. Stull, International Personal Protection Consultant, Vice Chair, ASTM F23 Committee on Protective Clothing; and three other occupational health experts. Mapa Professional (Willard, OH), which describes itself as "pioneers in hand protection," provide definitions and a chart of test data in their Chemical Resistance Guide (6) Technical representatives from Best and from Lab Safety Supply are always ready to provide specific assistance and more information (see sidebar: For more information, below).

TO SIDEBAR: For more information

When the protection becomes a recognized hazard
Because latex does provide a barrier to biological fluids, many health workers were already wearing inexpensive disposable latex gloves to protect them from the AIDS virus when OSHA enacted the Universal Precautions Standard (29 CFR 1910.1030) in 1992. The standard requires employers to provide gloves for employees exposed to bloodborne pathogens.

The current standard for hand protection in the chemical laboratory came in 1994. According to 29 CFR 1910.138, employers have the obligation to assess the job for chemical exposure, then select an appropriate glove (4). With the great increase in use of natural latex gloves, the gloves themselves are now a recognized hazard. Latex allergies present a serious risk to a significant number of users (1, p. 6).

TO SIDEBAR: Spectrum of latex allergy symptoms

Who is at risk?
In its 17-page alert in June 1997, NIOSH outlined the allergic reactions that may be triggered by exposure to latex (1). The more extensive the exposure, the more likely an individual will develop a latex allergy. Persons with a history of other allergic reactions are at even greater risk of becoming sensitized to latex. The NIOSH Alert warns, "Latex allergy is also associated with allergies to certain foods especially avocado, potato, banana, tomato, chestnuts, kiwi fruits, and papaya" (1). Robert G. Hamilton of the Johns Hopkins University School of Medicine's Reference Laboratory for Dermatology, Allergy and Clinical Immunology, describes the food connection as resulting from proteins in certain foods being "structurally similar" to known natural rubber latex allergens, and he adds wheat germ, corn, soybean, hazelnut, melon, passion fruit, tomato, and fig to the NIOSH list.

Exactly how many persons are at risk for or already suffering from the allergy is not known. Hamilton says, "In terms of prevalence of latex allergy in laboratory workers, we do not have an accurate estimate in the United States because we have not had the benefit of an FDA-licensed skin-testing extract. The serological tests for IgE anti-latex in the blood are good but not perfect in terms of diagnostic sensitivity and specificity. The general prevalence figure for latex allergy used by most investigators, based primarily on studies performed outside the United States, is approximately 10% of high-risk health care workers who use powdered latex gloves. Definition of latex allergy varies among studies and thus a definitive consensus number is not available. The CDC [Centers for Disease Control and Prevention] also uses the rough estimate of 10% of health care workers who are sensitized until more definitive prevalence studies are done."

According to Hamilton, "These allergic reactions are elicited by exposure to any of a group of highly aller-genic proteins that become airborne attached to cornstarch particles or get adsorbed into the body through direct contact of skin or mucosal surfaces with the rubber product." Cornstarch powder is used in some disposable latex gloves to make putting them on or taking them off easier. When the gloves are removed, the cornstarch containing allergenic proteins is scattered into the air. The sensitized person does not even need to be wearing the gloves to be exposed-just being near someone who is removing gloves could cause a reaction.

TO SIDEBAR: Evaluating laboratory gloves

The final word
When laboratory gloves are needed, the wearer has much to think about. If latex provides the best barrier and is the glove of choice, the possibility of an allergic reaction, especially from long-term exposure to powdered latex gloves, must be considered. The number of individuals suffering from a latex allergy may not be known, but for the unlucky ones, once sensitized, exposure to latex in any setting can trigger a reaction: rubber aprons in laboratories and office supplies such as rubber bands and erasers; toy balloons, automobile tires, and rubber boots, just to name a few latex-containing products. It is hard to get away from natural rubber.

REFERENCES

READER SURVEY: Tell CH&S About...Latex gloves in your laboratory