Jordan Hewes felt lucky. She had begun a series of experiments staining cell junctions when she discovered the hazardous and toxic properties of silver nitrate, the staining agent she was using. "I was very upset when I learned about the hazardous properties of silver nitrate," Hewes explained. "Besides being toxic, it ... reacts explosively with ethanol. I could have blown myself up. I was disappointed that my supervisor failed to warn me about the hazards before I started this project."
"Information that saves lives and prevents injury should be freely available to all."
While Hewes suffered no ill effects from this episode, her experience demonstrates the importance of a sensible hazardous-risk assessment plan for the use of toxic chemicals. In the above example, not only should the appropriate data about silver nitrate have been easily accessible to Hewes, she should have been trained how to locate the information and how to use it properly. Unquestionably, handling toxic chemicals involves much more than simply practicing common sense safety procedures like wearing gloves and a lab coat.
Situations like this spurred the Occupational Safety and Health Administration (OSHA) to develop the Hazard Communication Standard (29 CFR 1910.1200). In effect since 1985, the Hazard Communication Standard's purpose is "to ensure that the hazards of all chemicals produced or imported are evaluated, and that information concerning their hazards is transmitted to employers and employees. This transmittal of information is to be accomplished by means of comprehensive hazard communication programs, which are to include container labeling and other forms of warning, material safety data sheets, and employee training."
Regarded as the best general source of information for any given compound, material safety data sheets (MSDSs) are the primary means of hazard communication. As required by OSHA, the standard MSDS contains data in eight sections: the manufacturer, hazardous ingredients, physical and chemical characteristics, fire and explosive hazard data, reactivity data, health hazard data, precautions for safe handling and use, and control measures. While other formats exist, all MSDSs must provide the pertinent physical, chemical, and toxicological data required for working safely with a given chemical.
The Hazard Communication Standard, and the newer Laboratory Standard for academic and research labs enacted in 1991, specify that workers must have ready access to the MSDSs for each compound to which they may be exposed. Indeed, OSHA places a heavy emphasis on the Hazard Communication requirements; noncompliance carries fines up to $70,000 and more. For a large institution, however, the task of getting the proper MSDS to the right place can be particularly challenging. Ralph Stuart, the environmental safety manager for the University of Vermont at Burlington, explains, "Our campus has nearly 400 labs with at least 100 chemicals each. Because our purchasing department places all the orders for chemicals, it frequently receives the MSDSs from the suppliers. Unfortunately, the MSDSs do not always make it from there to the researchers who originally placed the orders." To solve this problem, Stuart's department established and maintains the Vermont SIRI MSDS Archive Web page (http://siri.uvm.edu/msds), providing free access to at least 180,000 MSDSs.
Similarly, Robert Toreki
, associate professor of chemistry at the University of Kentucky, writes and maintains "Where to Find MSDSs on the Internet" (www.ilpi.com/msds/index.chtml
). This page has links to more than 60 Internet sources for free MSDS information grouped in various categories and features a section of "frequently asked questions" about MSDSs. Toreki's motivation for maintaining this popular site is simple. "I've seen some horrible lab accidents, including a couple where people have been nearly killed," he said. "I developed a strong personal belief that information that saves lives and prevents injury should be freely available to all." Certainly, the 1,900 hits his Web site has on peak days speak loudly about the need for this information.
In contrast to the situation faced by Stuart at the University of Vermont, smaller companies and laboratories must tackle a different set of hazard communication problems. Joyce Skalicky, an environmental safety coordinator for Medtronic Inc. of Anaheim, Calif., runs the company hazard communication program with a strong hands-on approach. A medical device manufacturer, Medtronic often hires lay people to work in its production facility. "Because these individuals usually don't have any experience working with chemicals, I review with them the specific MSDS for each chemical they use during our new-hire and annual training classes," she says. Skalicky requires each department to maintain its specific set of MSDSs, and subjects them to the chemical inventory verification checks she performs quarterly. Also, her approval is required for all chemical orders, and she insists on obtaining MSDSs directly from the manufacturers of the reagents Medtronic uses.
Armed with the information provided by an MSDS, how do researchers use it to protect themselves from the hazards of toxic chemicals? An excellent procedure for assessing the risk of a toxic chemical and then planning to use it safely, with an emphasis on the interaction between the scientist and the compound, is clearly explained in a videotape entitled "Assessing Risks of Toxic Chemicals." Produced by the Office of Laboratory Safety at the Howard Hughes Medical Institute (HHMI), this tape offers sound advice with real-life examples from the laboratory. (Offered as a public service, this and other safety videos are available through the HHMI Web site at www.hhmi.org/science/labsafe).
|Relative Toxicity Levels|
|Toxicity Level||LD50-Rat||Probable Lethal Dose for Humans|
|Extremely toxic||1 mg/kg or less||Less than 1 gram |
|Highly toxic||1 to 50 mg/kg||Several grams |
|Moderately toxic||50 to 500 mg/kg||1 ounce |
|Slightly toxic||500 to 5000 mg/kg||1/2 pound |
|Practically nontoxic||5000 to 15,000 mg/kg||1 pound |
|Relatively harmless||15,000 mg/kg and up||1 quart|
|Source: J.T. Dufour et al., Hazard Communication Handbook, revised ed., Sacramento, Calif., California Chamber of Commerce, 1990, page 90.|
As explained on the tape, the risk of a toxic effect from a compound depends on the inherent toxicity of the compound and the extent of exposure. A clear understanding of these factors then leads to the necessary measures for safe and proper handling. To begin with, facts about a chemical's inherent toxicity are found in the health hazard data section of an MSDS. Specifically, this section provides information about the compound's acute and chronic toxicity. Acute toxicity, or the adverse effects from a single dose or exposure to a substance, is quantified by the LD50
. The LD50
is the single dose of the compound expected to kill 50 percent of a group of test animals and is usually expressed as milligrams of substance per kilogram of animal body weight. These values correspond to a relative toxicity scale running from "extremely toxic" to "relatively harmless" (see table above). For example, the LD50
in the rat for sodium azide, a chemical frequently used as a preservative of laboratory reagents, is 27 mg/kg, earning sodium azide a "highly toxic" rating. Bear in mind, however, that the LD50
value is only an estimate of the relative toxicity of a substance. It should not be used as an absolute level of intake considered safe or unsafe for human beings.
While more difficult to quantify than acute toxicity, chronic toxicity is defined as the adverse effects that result from repeated exposure to a substance over a relatively long period, and moves into the areas of mutagenesis, cancer, and neurological disorders. For sodium azide, chronic effects include alteration of genetic material, testicular damage, and blindness, to name a few.
With an understanding of a chemical's inherent toxicity, the next task is to grapple with the extent of exposure. Four parameters require consideration: dose, duration of exposure, frequency of use, and the route of exposure. Dose, or the amount of a substance one could be exposed to during a procedure, provides a good warning of potential hazards, particularly when that amount is compared to the LD50. value. Also, the route of exposure as described on the MSDS, be it ingestion, inhalation, contact with the skin, or injection, suggests what types of personal protective equipment are needed. Understanding and controlling these parameters greatly reduces the likelihood of exposure to a toxic substance. When duration of exposure and frequency of use are minimized, the risks of chronic toxicity fall dramatically.
Of course, the physical and reactivity characteristics of a chemical and its toxicity data need consideration during procedure planning. Hence, before working with a toxic chemical, develop procedures to use the smallest amount of the compound possible and consider a less toxic alternative.
George H. Wahl Jr.
During the course of a professional lifetime, a laboratory worker encounters hundreds of chemicals. Dangerous, accidental exposure to a toxic substance can occur, so it behooves researchers to minimize exposure. To that end, the National Academy of Sciences' Prudent Practices in the Laboratory: Handling and Disposal of Chemicals
(Washington, D.C., National Academy Press, 1995), fosters a new culture of laboratory safety. Structured around its formal framework for experimental planning, Prudent Practices
stresses a continuous basic respect for the health and safety of laboratory workers by emphasizing experimental planning and habitual risk assessment. In the words of George H. Wahl Jr.
, professor of chemistry at North Carolina State University and a consultant on the Hazard Communication Standard, " Prudent Practices
is the work of intelligent practitioners, rather than lawyers and bureaucrats. It has become the gospel for safe chemical handling procedures in the lab."
According to W. Emmet Barkley, director of the HHMI Office of Laboratory Safety and a member of the National Research Council's Committee on Prudent Practices for Handling, Storage, and Disposal of Chemicals in Laboratories, the interaction between the scientist and the compound takes the highest priority when assessing the risk of toxic chemicals. While the basic toxicity data supplied on an MSDS is important for this assessment, much of the other data often is not very useful to lab workers, usually because of liability issues. "Frequently," he says, "the complexity of the MSDS has no relationship to the risk of handling a compound." As a result, the Committee on Prudent Practices has prepared Laboratory Chemical Safety Summaries (LCSSs) for 88 chemicals commonly used in the research laboratory. Incorporated into Prudent Practices in the Laboratory, the LCSSs are designed expressly for laboratory workers. These summaries provide information on handling, storage, disposal and emergency response, and have applications with other structurally related compounds.
Finally, the advice of knowledgeable people goes a long way in risk assessment. Although occasionally seen as an impediment to research because of its job of enforcing safety regulations, a university's office of environmental health and safety (EHS) is an excellent resource. As stated by John Chan, manager for industrial hygiene at the University of California at Irvine, "We want our researchers to regard EH&S as an asset and resource rather than an enemy, as we work together toward the common goal of research and education."
| Excerpts from Material Safety Data Sheet|
AMI-THERM © NX08and NX16
|1. CHEMICAL PRODUCT AND COMPANY IDENTIFICATION|
|Trade Names-Synonyms||AMI-THERM®- para-aramid/meta-aramid felt and needled felt in various forms - cloth, tapes, etc.|
|Product Identification||NX08 and NX16.|
|Chemical Name-Synonyms||poly(terephthaloylchloride/p-phenylenediamine) /poly(isophthaloylchloride/m-phenylenediamine) fibers - para-aramid/meta-aramid felt.|
|Manufacturer's Name||Auburn Manufacturing, Inc|
P. O. Box 220 Mechanic Falls, ME 04256
|Date prepared||September 30, 1993|
|Revised||July 6, 1998|
|3. HAZARDS IDENTIFICATION|
PRIMARY ROUTES OF EXPOSURE:
|Inhalation and skin contact.|
|HEALTH HAZARDS (Including acute and chronic effects and symptoms of overexposure):|
|ACUTE:||Inhalation:||Inhalation of dusts and fibers may result in irritation of the upper respiratory tract (mouth, nose and throat).|
| ||Skin Contact:||Skin contact with dusts and fibers may produce itching and temporary mechanical irritation.|
| ||Eye Contact:||Eye contact with fibers and dusts may produce temporary mechanical irritation.|
| ||Ingestion:||Temporary mechanical irritation of the digestive tract. Observe individual. If symptoms develop, consult a physician.|
|CHRONIC:||See carcinogenicity section below. There are no known health effects associated with chronic exposure to this product.|
|4. FIRST AID MEASURES|
|Inhalation:||Move individual to fresh air. Seek medical attention if irritation persists.|
|Skin Contact:||Wash with mild soap and running water. Use a washcloth to help remove fibers. To avoid further irritation do not rub or scratch irritated areas. Rubbing or scratching may force fibers into the skin. Seek medical attention if irritation persists.|
|Eye Contact:||Flush eyes with flowing water for at least 15 minutes. Seek medical attention if irritation persists.|
|Ingestion:||N. A. (Not Applicable)|
|8. EXPOSURE CONTROLS / PERSONAL PROTECTION|
|VENTILATION:||General dilution ventilation and/or local exhaust ventilation should be provided, as necessary, to maintain exposures below PEL's or TLV's. Adequate ventilation must be provided at elevated temperatures.|
|RESPIRATORY PROTECTION:||A properly fitted NIOSH/MHSA approved disposable dust respirator such as the 3M model 8710 or model 9900 (in high humidity environments) or equivalent should be used when: high dust levels are encountered; the level of fibers in the air exceeds the OSHA permissable exposure limits; or if irritation occurs. Use respiratory protection in accordance with your company's respiratory protection program and OSHA regulations under 29 CFR 1910.134. |
When processing meta-aramid fiber products at elevated temperatures or in a way that creates airborne DMAC, wear NIOSH/MHSA-approved organic vapor cartridge respirators if there is a potential for exposures in excess of the applicable limits.
|EYE PROTECTION:||Safety glasses, goggles or face shields should be worn whenever materials are being handled.|
|PROTECTIVE CLOTHING:||Wear loose fitting, long sleeved shirt that covers to the base of the neck, and long pants. Skin irritation from exposure to fibers is known to occur chiefly at pressure points such as around the neck, wrist and waist. Wear gloves when handling product. |
|WORK/HYGIENIC PRACTICES:||Handle in accordance with good industrial hygiene and safety practices: |
- Avoid unnecessary exposure to dusts and fibers
- Remove fibers from skin after exposure
- Be careful not to rub or scratch irritated areas. Rubbing or scratching may force the fibers into the skin. The fibers should be washed off. Use of barrier creams can, in some instances, be helpful.
- Use vacuum equipment to remove fibers and dusts from clothing. COMPRESSED AIR SHOULD NEVER BE USED. Always wash work clothes separately and wipe out the washer/sink in order to prevent loose glass fibers from getting on other clothes.
- Keep the work area clean of any dusts and fibers generated during fabrication. Use vacuum equipment to clean up dusts and fibers. Avoid sweeping or using compressed air as these techniques resuspend dusts and fibers into the air.
- Have access to safety showers and eye wash fountains.
- For professional use only. Keep out of children's reach.
Michael D. Brush is a safety officer and researcher with a biotechnology company in Irvine, Calif. E-mail: MDBrush@compuserve.com