Environmental Health & Safety

Second Quarter 1999

"The superior man, when resting in safety, does not forget that danger may come. When in a state of security he does not forget the possibility of ruin. When all is orderly, he does not forget that disorder may come. Thus his person is not endangered, and his States and all their clans are preserved."

WILL YOUR GLOVES PROTECT YOU?

Many researchers perform their laboratory work wearing the gloves that have been provided without ever questioning whether or not the gloves will really protect against the hazardous materials being used.  There is a belief that if gloves are being worn, their hands are protected.  This is not always the case.

Most of you are probably aware of the incident that occurred in 1997 when a researcher at Dartmouth University died as a result of mercury poisoning.  It is believed that mere drops of dimethyl mercury splashed onto her gloves.  Follow-up studies estimate that it would take less than 15 seconds to pass through the latex gloves she wore and permeate her skin.  Less than a year from initial exposure, this extremely toxic material claimed her life.

Although fatalities in the research environment are extremely rare, this case reminds us that glove choice is an important consideration.  Although most cases of laboratory exposure never approach this level of severity, common exposures can result in effects that range from minor irritation to chemical burns or even potential long-term health effects.

For this reason it is important to choose the appropriate glove for the job at hand.  The obvious question is, "How do I know if a glove will protect me?"  A quick reference available to all labs is to consult the chemical manufacturer's material safety data sheet (MSDS).   Unfortunately, the information provided on MSDSs is often vague and conservative.  Phrases such as "wear appropriate chemical resistant gloves" do not provide much help.  In response to spills most MSDSs insist on maximum safety by instructing a responder to wear "heavy rubber gloves" when dealing with anything from dimethyl mercury to table salt.

A more helpful reference is the glove chart provided by the glove manufacturer.  This information is based on actual tests run by the company for specific chemical hazards.  Many of these glove charts can be found on the company's Web Pages and most manufacturers will be happy to send you a copy. The one problem associated with these glove charts is that currently the manufacturers can provide this information for only a limited number of chemicals. In the research setting, we often use materials not on these charts or in concentrations different from those tested.

Fortunately, more information is becoming available all the time, and a few simple guidelines can greatly reduce the probability of contamination leading to an exposure.  Since most of the work at TSRI involves incidental contact as opposed to that of industrial workers who must place their gloved hands directly into the greases or cleaning agents, one should always change gloves immediately upon noticing that contamination of the glove has occurred.  Furthermore, regularly changing gloves will reduce the potential exposure time of unseen contamination and should be performed routinely.  Double gloving is encouraged anytime the possibility for contamination is expected.  Generally speaking, doubling the glove thickness will increase the breakthrough time fourfold. Recently, the staff at Cornell University devised a set of guidelines that concentrates on typical research laboratory agents.  As with most glove charts, the data takes into account not only breakthrough times but also the severity of a potential exposure.  Some of this information is provided below.  Please contact the Health and Safety Office if you would like more information concerning this report.

 

CHEMICAL	RECOMMENDED GLOVE TYPE
Acetic Acid	nitrile(4mil), latex, or vinyl
Acetone	butyl rubber or latex
Acetonitrile	nitrile
Acrylamide	nitrile
Benzotriazole	nitrile
Carbon disulfide	double glove with heavy weight (8 mil) nitrile
Carbon tetrachloride	double glove with heavy weight nitrile
Chloroform	double glove with heavy weight nitrile
Dimethyl sulfoxide (DMSO)	nitrile
Ethanol	nitrile
Ethidium Bromide	nitrile, double glove when using stock materials
Formaldehyde	nitrile
Formamide	nitrile
Formic acid	double glove with heavy weight nitrile
Hexane	double glove with heavy weight nitrile
Hydrochloric acid	nitrile, neoprene or butyl rubber when direct contact is expected
Hydrofluoric acid	double glove with heavy weight nitrile, neoprene or butyl rubber when contact is expected
Liquid nitrogen	thermal
Mercury	nitrile
Methanol	nitrile
Methylene chloride	double glove with heavy weight nitrile
Paraformaldehyde	nitrile
Phenol	double glove with heavy weight nitrile
Phosphoric acid	double glove with nitrile
Propionic acid	nitrile
Sodium azide	nitrile
Sulfuric acid	heavy weight nitrile
Tetrahydrofuran (THF)	double glove with heavy weight nitrile
Toluene	double glove with heavy weight nitrile
Xylene	nitrile

The list detailed above is intended only as a guideline and is designed primarily to address incidental contact only. It must be stressed that this information should never be used to supplant the information given on a manufacturer's glove chart. Variations in manufacturing techniques and the exact composition of gloves may vary. Always respect the manufacturer's glove chart first.

The use of Latex gloves is only appropriate for:

* Most biological materials
* Nonhazardous chemicals
* Radioactive materials
* Very dilute or aqueous solutions of hazardous chemicals

People have used asbestos for many centuries. Around 430 B.C., the Greek geographer, Pausanias, spoke of golden lamps with incombustible wicks made of "Carpathian flax." The ancient Romans reportedly placed, upon their death, some members of their society into asbestos clothes prior to cremation in order to conserve their ashes. The French emperor Charlemagne is said to have had a tablecloth made of asbestos that he would clean by passing it through fire, thereby impressing both friends and enemies.

Asbestos was recognized as a health concern very early. Pliny the Elder, the Roman naturalist, and Strabo, the Greek geographer, both wrote of "lung sickness" observed in slaves who wove asbestos into cloth. However, it was not until the results of an epidemiological study published in 1930 that chronic respiratory disease attributed to asbestos exposure was recognized by the modern world, and it was not until 1949 that the cancer-producing effects of asbestos exposure were recognized.

What is asbestos?

Asbestos is a term that is used to identify six naturally occurring minerals. These fibrous, silicate materials crystallize into narrow "veins" of parallel bundles comprised of extremely small, single crystal fibrils. The fibers themselves are strong, durable, and resistant to fire and heat. Additionally, they are long, thin, and flexible. The unique properties of high thermal stability, excellent tensile strength, chemical resistivity, good thermal and electrical resistance, and the ability to be divided into fibers made asbestos ideal for many applications and uses such as for insulation, as reinforcements for cement and flooring applications, and in friction products such as automobile brake linings. However, despite the strength of the individual fibers, physical disturbance of the bundles can cause them to break down into finer bundles or individual fibers. It is when these fibers become airborne that asbestos becomes a major concern. Aside from accumulating in the lungs, the particles can move into the pleura and into the lymph nodes. From there, they can travel to other parts of the body. Ingested asbestos fibers are also of concern but less so than the inhaled fibers. Ingested asbestos can stick in the intestinal tract and then move into the lining of the abdomen. Once inside the body, a variety of diseases may develop.

Types of asbestos

There are six recognized types of asbestos: chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite. All of these minerals may occur naturally in nonfibrous form. When in the nonfibrous form, they are not classified as asbestos and are not considered hazardous.

Fibrous asbestos minerals can be divided into two major categories, amphibole asbestos and serpentine asbestos. Within these two groups, the three types of asbestos that have commercial value are chrysotile (white asbestos), amosite (brown asbestos), and crocidolite (blue asbestos).

Amphibole fibers (amosite and crocidolite) are extremely hazardous. Their relatively short (compared to other types of asbestos), brittle fibers make them more likely to become airborne and their straight, needle-like fibers allow them to become permanently imbedded in lung tissue. Crocidolite is the strongest of the asbestos fibers. It has high tensile strength and is acid resistant. Amosite is highly resistant to heat and is very flexible. It may, however, be susceptible to acids and alkalines. Also, it has less tensile strength than either chrysotile or crocidolite and it has only fair spinnability.

Conversely, the silky, curly, serpentine fibers (chrysotile) are much less hazardous than the amphibole fibers. They stay airborne for less time than amphibole fibers and are therefore less likely to be inhaled. The human body is capable of eliminating them relatively quickly. Chrysotile fibers have high tensile strength, high flexibility, good spinnability, and are resistant to alkalines.

Use of asbestos

Today, chrysotile or white asbestos accounts for approximately 99% of the world's asbestos production. Chrysotile is primarily used in cement building materials such as roofing materials, cladding, and cement pipes. These building materials account for about 90% of the chrysotile used today. Friction product uses account for approximately 7% of the chrysotile produced, with some plastics and miscellaneous applications accounting for the remaining 3%. All of the current applications are high-density products that contain the fibers in a matrix of cement or resin and, therefore, pose little risk of becoming airborne.

Much of the controversy concerning asbestos arose from the risks associated with asbestos fibers in products that are prohibited today. However, up until the 1970s, asbestos fibers were used in a wide variety of products such as toasters, ironing boards, and other low-density friable insulation products. Friable material can be easily crumbled and reduced to powder by hand pressure and is thus capable of becoming an airborne hazard. Nonfriable material does not share the characteristics of friable material. As you might expect, friable material is more likely to cause the release of airborne fibers than would nonfriable material. Asbestos was also used in various fire-resistant, thermal, and acoustic insulation applications including pipe and boiler insulation material. These applications are no longer allowed in most countries due to the risk to workers during the installation and removal processes. Although the use of asbestos has been dramatically curtailed, it is not unusual to encounter asbestos in older buildings and facilities. As such, care must be exercised during repair, demolition, or remodels of older buildings and facilities.

Asbestos at work and at home

Because of the wide use of chrysotile, it is not surprising that this form of asbestos has been identified in areas of the Stein Research Building. Chysotile has been identified in the floor tile mastic (adhesive) and it is considered to be contained in the floor tiles throughout the building. As such, while the building undergoes renovation, a licensed, asbestos-abatement contractor is removing the asbestos-containing materials. Containment areas are set up as required, and air sampling is conducted to ensure that there is no asbestos contamination in occupied areas of the building.

If your house was built before 1983, there is a possibility that it may have some asbestos-containing material somewhere within the house. Asbestos was used in ceilings, siding, vinyl flooring, gypsum drywall, and pipe insulation. The only way to know for sure is to have a sample analyzed in a laboratory.

If areas within your home do contain asbestos, several other alternatives may be considered before removing the asbestos. If the material is unlikely to be damaged or disturbed, leaving it in place is one option. If there is a possibility of damaging the material, it may be encapsulated. Some encapsulants soak into the material and bind the fibers while others seal only the surface of the material, like a coat of paint. The asbestos material remains and may have to be removed at a later date, but the encapsulation will minimize the chance of asbestos becoming airborne.

If you would like additional information about asbestos or asbestos removal, please contact Environmental Health and Safety at 4-8240.