A PROPOSAL FOR CHEMICAL SAFETY PRACTICES

CHEMICAL SAFETY LEVELS (CSLs):

A PROPOSAL FOR CHEMICAL SAFETY PRACTICES

IN MICROBIOLOGICAL AND BIOMEDICAL LABORATORIES

Robert H. Hill, Jr., Jean A. Gaunce, and Pamela Whitehead ^1.

Office of Health and Safety, Centers for Disease Control and Prevention

1600 Clifton Road (A17), Atlanta, GA 30333

^1. Ms. Whitehead, as a student intern from the University of Georgia, worked at CDC in developing this project. She is now employed at IMTS, Inc., Buford, Ga.

ABSTRACT

Microbiological and biomedical laboratories handle chemicals of varying hazards in many diverse manners and quantities. While there are biosafety levels which classify laboratories by the hazard of the biological agent and its use, there are no similar guidelines for classifying chemical safety practices. We propose a system for using chemical safety levels (CSLs) in these laboratories. These CSLs - CSL1, Low Risk; CSL2, Moderate Risk; CSL3, Substantial Risk; CSL4, High Risk - are classified by the chemical hazards and the nature of the work with these chemicals in the laboratory. Risk at each CSL is governed by limiting or restricting chemical usage or type of work. Standard and CSL-specific safe practices, equipment, and facilities requirements are proposed. This work is presented as a starting basis for developing a CSL system, and additional details and modifications are to be worked out through a pilot project.

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INTRODUCTION

Microbiological and biomedical laboratories handle chemicals of varying hazards in many diverse manners and quantities. The result of this diversity is that the risk of chemical exposure in these laboratories is often difficult to assess and the safety requirements are not clearly understood. Scientists and laboratorians in microbiological and biomedical laboratories are often trained primarily in the biological sciences, often focus on biological safety, and may not have strong backgrounds in the hazards of chemicals and chemical safety. Nevertheless, most have a strong desire to conduct their work in the safest possible manner, often seeking guidance in chemical safety.

There are specific biosafety guidelines for microbiological and biomedical laboratories for handling bacterial, viral, and other microbial agents of varying hazard. These guidelines are described in terms of biosafety levels (BSLs) and are found in the Biosafety in Microbiological and Biomedical Laboratories (BMBL) publication by the Centers for Disease Control and Prevention, and the National Institutes of Health (1). The advantage of the guidelines is that the microbiological agent and its use determines the risk and the BSL defines the optimum level of protection required for worker protection in the use of that agent. This BSL definition helps the researcher, laboratorian, supervisor, manager, and health and safety personnel identify more clearly the features of the facilities and the work practices required to protect the laboratory worker from exposure to biohazardous agents. These guidelines are widely accepted and highly successful in the microbiological and biomedical communities, who frequently want to know what BSL should be used in a given situation.

There are no similar, widely-recognized guidelines which classify these same laboratories using chemicals according to their relative risk. In this paper we propose a classification system of chemical safety levels or CSLs. The CSL assigned to a laboratory will be dependent upon the risks associated with chemicals being used, including: 1) the hazards of each chemical - for instance, chemical properties, flammability, reactivity, toxicity, and reported health effects; and, 2) the nature of the work, i.e. the activity or process in which the chemical will be used and the concentration or quantity of the chemical being used. A laboratory classification system for chemical work, described by Dr. Keith Furr, provided a genesis for some of the ideas for CSLs proposed in this paper (2). A system has been described for laboratories using radionuclides, and another system has been designed for chemical carcinogens (3,4).

Four CSLs will be determined, in a manner similar to BSLs, by the degree of risk of hazardous chemical exposure: low risk [CSL1], moderate risk [CSL2], substantial risk [CSL3], and high risk [CSL4]. Each level of risk will be addressed separately in sections that describe kinds of chemicals allowed, standard and special safety practices, standard and special safety equipment, and standard and special laboratory facility requirements. These requirements were drawn from several sources (2,5-13).

The appropriate CSL will be posted immediately outside each laboratory, allowing laboratorians, facility support workers, and health and safety personnel to know the relative hazard of the chemical work and the degree of protection required in that laboratory. By assigning a CSL to each lab, the worker should know upon entering the lab what kind of chemical hazards are likely to be present and better know what precautions should be exercised in emergency situations. Laboratorians must be trained and knowledgeable of the four different CSLs to benefit from this classification. It is the responsibility of the employer or laboratory director to ensure all laboratorians are trained and knowledgeable about the risks from chemicals while working in the laboratory (13).

DESIGNATION OF CHEMICAL SAFETY LEVELS

After consultation with the laboratory supervisor, a safety and health professional or Chemical Hygiene Officer, usually in the institution’s Environmental, Health, and Safety Office (EHS), will designate the CSL for each laboratory. This CSL designation is based upon: 1) the specific hazards of the chemicals being used; and 2) the nature of the work and the risk of exposure to hazardous chemicals during laboratory operations. The hazards of chemicals may be broadly categorized into Chemical Hazard Classes as defined in Table 1. Assigning hazard classes will aid in assessing a laboratory’s chemical risks. The four CSLs are described below.

CSL1 Laboratories - Low Risk

Typical Laboratory Operations: CSL1 is appropriate for work that does not require special engineering design features or containment equipment. The requirements for this level are generally those of good laboratory work practice. Hazardous chemicals are not to be used openly in CSL1 laboratories. Workers may use small vials that are often sealed with septum tops or screw caps for sampling by syringe or pipette. Typically instrumental laboratories may fit into the CSL1 category.

Chemical Use: HIGHLY RESTRICTED. Only low hazard chemicals (see Table 1) may be used openly.

Quantities Allowed: Low hazard chemicals may be used as needed. Volatile, toxic, flammable, reactive, corrosive, or other high hazard chemicals are not used or stored in the lab except in sealed vials, usually containing 1 ml or less of solution.

Exposure Risk: There is a low risk for exposure due to the restrictions in the use of hazardous chemicals.

CSL2 Laboratories - Moderate Risk

Typical Laboratory Operations: CSL2 is appropriate for laboratory work with moderate risk chemical operations. Use of hazardous chemicals is permitted but in such a way as to minimize quantities being used and stored. Typically work is with biological agents with occasional use of hazardous chemicals in small quantities.

Chemical Use: LIMITED and RESTRICTED. Chemicals with low to moderate hazard risk may be used openly and stored in needed quantities. Hazard Class 3 chemicals are limited in quantities used and stored in each laboratory. Hazard Class 4 chemicals are restricted (see Table 2), and are not permitted in CSL2 laboratories except by special exemption by the EHS. Requests for special exemption are reviewed to determine if work with this chemical can be carried out in that laboratory safely.

Quantities Allowed: Low hazard chemicals may be used in quantities needed. Hazard Class 3 chemicals (see Table 3) are not available in quantities greater than 1 liter (liquids) or 0.5 kilogram (solids). Hazard Class 4 chemicals in the restricted classes are not permitted except by EHS special exemption which specifies allowed quantities and permitted work processes.

Exposure Risk: The moderate risk for exposure is controlled by limiting and restricting types and quantities of chemicals.

CSL3 Laboratories - Substantial Risk

Typical Laboratory Operations: CSL3 is for chemical operations with a substantial risk requiring engineering controls. Chemical fume hoods or ventilated enclosures are required for containing operations that produce significant amounts of gas, vapors, or particulate. Chemicals of varying hazard, including Hazard Classes 3 and 4, are used. These laboratories are often regarded as chemical laboratories. EHS reviews operations with high hazard chemicals recommending methods to minimize exposure and risk .

Chemical Use: GENERALLY UNRESTRICTED. Chemicals of substantial and high risk hazard are not restricted and may be used. Work with Hazard Class 4 chemicals is reported to EHS, but special exemption is not required. Nevertheless, some operations may require further restrictions if they are considered high risk, involving substantial potential exposure to or contamination by high hazard chemicals, such as in the synthesis or isolation of highly toxic chemicals or the use of large quantities of high hazard chemicals. These types of operations may require work in a CSL4 facility.

Quantities Allowed: Quantities of chemicals in Hazard Class 3 and below are limited only by need and local fire codes. Hazard Class 4 chemicals may be used in needed quantities, but their hazards dictate use and storage in minimum quantities only.

Exposure Risk: The substantial risk for exposure to high hazard chemicals is controlled by using stringent engineering controls, by minimizing chemical use and storage, and by carefully reviewing work practices.

CSL4 Laboratories - High Risk

Typical Laboratory Operations: CSL4 is for chemical operations where there is high risk of potential exposure to high hazard chemicals. There are special engineering features, containment equipment, and work practices designed to provide multiple barriers for protection of workers. This is typically a special purpose laboratory involving production or isolation of high hazard chemicals and contamination of equipment and facilities is likely to occur.

Chemical Use: UNRESTRICTED. Use of all chemicals, including high hazard chemicals, is unrestricted and governed only by prescribed protocols which dictate safe handling and storage procedures. Special facility design and equipment may be needed prior to work with these chemicals.

Quantities Allowed: Limited only to the need. High hazard chemicals should be limited to the quantities required.

Exposure Risk: There is potential high risk of exposure and contamination during operations using high hazard chemicals. Risk is controlled by using stringent engineering controls and facility design requirements, by minimizing chemical use and storage, and by carefully defining and monitoring work practices.

SAFETY GUIDELINES FOR CHEMICAL SAFETY LEVELS

The guidelines for safety practices, safety equipment, and laboratory facilities are described below for each CSL. All CSLs must meet minimum standard guidelines. These are the only guidelines for CSL1 laboratories. CSL2, CSL3, and CSL4 laboratories have additional special guidelines. A summary of the guidelines for each CSL is listed in Table 4.

Standard Safety Practices for CSL1 through CSL4

1. Cardinal Rule: Minimize Exposure to All Laboratory Chemicals. Minimize risk of exposure: a) by using and storing minimum quantities of chemicals; and b) by using ventilation and engineering controls, appropriate personal protective equipment, and good laboratory work practices. Always check the performance of your ventilation and engineering controls before starting any work.

2. Eye protection is required for all personnel and visitors in all locations where chemicals are used or stored. At a minimum, safety glasses with side shields are required in laboratories. Contact lenses may not present a significant hazard in the laboratory, and may in many cases be protective (18). Nevertheless contact wearers should also wear at a minimum safety glasses with side shields .

3. Protective gloves must be chemical- and purpose-specific and are selected on the basis of the chemicals being used.

4. Planning shall be guided by these principles: i) ensure that the chemical with its inherent hazards can be used safely in your laboratory, i.e., you have the proper facilities and available resources to safely carry out this work; ii) whenever possible substitute less hazardous alternatives for high hazard chemicals; iii) use the smallest quantity of chemical that is practical for the experiment or test; and iv) purchase the minimum quantity needed to conduct all experiments.

5. Limit access to the laboratory to authorized personnel during operations and to others as designated by the laboratory supervisor.

6. Post signs at the entrance identifying hazards, telephone numbers of supervisors and emergency contacts, and the CSL designation for the laboratory.

7. Maintain the laboratory in a neat and orderly manner. All secondary containers are properly labeled. Refrigerators and freezers are cleaned at least annually, and when there has been an overt spill.

8. Eating, drinking, and smoking are not allowed in the laboratory, and food or drink are not stored in the laboratory. Microwave ovens within lab areas are not to be used for heating food or drinks. Cosmetics are not applied in the laboratory.

9. All emergency equipment is maintained in proper working order and is checked at least annually. Exits and access to emergency equipment - such as fire extinguishers, electrical panels, emergency eye washes and showers - are not obstructed.

10. All personnel are trained in emergency procedures and know the location of emergency equipment including: emergency eye washes and showers, fire extinguishers, fire alarms, emergency exits, telephones, chemical spill kits, and personal protective equipment. Training is documented.

11. A chemical inventory is maintained continually or at least annually. Chemicals are dated upon receipt. Outdated or unneeded chemicals are sent for disposal. Ethers and other materials which form peroxides are disposed of no more than 12 months after purchase, even if unopened.

12. All chemicals must be stored properly, according to compatibility. Chemicals which pose significant hazard or risk shall be limited to minimum quantities required to meet short-term needs of the research program. Chemicals not in use shall be stored in appropriate chemical storage cabinets, not on floors or in hoods. Regulated chemicals and high hazard chemicals, such as drugs, radioactive materials, or highly toxic chemicals, require special secured storage areas.

13. A Chemical Hygiene Plan, including a laboratory-specific plan, is available for each laboratory as required by the Occupational Safety and Health Administration [OSHA] (29 CFR 1910.1450) (13). This Chemical Hygiene Plan includes Material Safety Data Sheets (MSDSs) for all chemicals used in the laboratory.

14. Chemical waste labels identify the contents of each container of chemical wastes and are placed on appropriate containers for disposal through the chemical waste disposal program. Wastes posing special hazard, i.e., reactive or highly toxic, are isolated for special handling.

15. Maintenance and emergency personnel are advised of potential hazards and proper precautions prior to entry into the laboratory.

Standard Safety Equipment for CSL1 through CSL4

1. One or more fire extinguishers meeting the laboratory’s specific needs are available in each laboratory.

2. Management must provide to each laboratory worker appropriate protective clothing and personal protective equipment, including gloves, lab safety glasses or goggles, laboratory coats, and respirators as needed. Personnel are properly fitted for respirators after medical clearance, and are trained and certified in the proper use of these respirators by EHS.

3. Emergency eyewash stations are provided in each laboratory using chemicals and are flushed weekly by lab personnel. Emergayety Emergency showers are located within 10 seconds walking distance and shall be tested at least monthly. Eyewash stations must and showers meet ANSI Z358.1 performance standards (19). The plumbing is sized to accommodate the deluge shower and the eyewash

Standard Laboratory Facility Guidelines for CSL1 through CSL4

1. Laboratory floors are designed for easy cleaning. Seamless floors which form curved junctions at the walls are best. Tile floors are also acceptable, but less desirable because chemicals may get into the seams. Carpeting is unacceptable in a laboratory setting.

2. Bench tops are non-porous, chemically-resistant, and seamless to the extent possible.

3. Furniture is maintained in sturdy and workable condition. Damaged furniture is repaired or replaced.

4. Aisle spaces are at least 44 inches wide and aisles are not used for permanent storage or for equipment location.

5. Electrical outlets are equipped with high-quality, low-resistance ground connections. Circuit breakers in all electrical panels are clearly labeled so that laboratory outlets and equipment circuits can be easily identified. Ground-fault interrupters are required within six feet of sinks.

6. All laboratory supply air is single-pass and not recirculated. Air flow should be directional from offices, corridors, and other auxiliary spaces into the laboratories, i.e. the laboratory air flow is negative with respect to the corridor. Outdoor air intakes are constructed so that re-entrainment of exhausted vapors does not occur.

CHEMICAL SAFETY LEVEL 2 - A Moderate Risk Facility

In addition to the standard practices, equipment, and facility guidelines, the following guidelines are recommended for CSL 2 laboratories.

Special Safety Practices for CSL2 -

1. Work with chemicals of Hazard Class 2 or greater in any category is performed in vented chemical fume hoods or Class II biological safety cabinets [BSCs] (8). However, there are limitations and precautions for using chemicals in BSCs. Non-volatile toxic chemicals may be used in BSCs but the quantities should be kept to a minimum to prevent possible damage to their HEPA filters. BSCs vented through thimble connections [Class II B3] or hard ducts [Class II B2] may be used for handling only “minute” quantities of volatile chemicals (8) with a Hazard Class 3 rating or less. Do not use Hazard Class 4 flammables in BSCs. Using larger quantities of flammables within BSCs increases the risk of fire or explosion, since the internal blowers are not spark-proof. Never use volatile chemicals in unvented BSCs [Class II A].

2. Entrance to these facilities may be secured during working hours. These facilities are secured during non-working hours.

Special Safety Equipment for CSL2

1. Class II BSCs (8)

2. Refrigerators or freezers used for storage of volatile, flammable chemicals or samples containing volatile, flammable chemicals shall be rated as laboratory-safe or explosion-proof (10). Refrigerators or freezers shall be labeled “No Food or Beverages” or “Chemicals Only”.

3. A flammable storage cabinet, either built-in or free-standing, is for the storage of flammable materials. Cabinets meet requirements of NFPA 30, NFPA 45, and OSHA standards described in 29 CFR 1910.106 (9,10,12).

4. Carts or safety carriers of rubber or polyethylene are provided and used for the transport of bottles of acids, bases, solvents, or other hazardous chemicals.

5. Spill control kits are available and laboratory personnel are trained in their use. Spills or accidents are promptly cleaned up. All spilled material and associated clean-up materials should be disposed of as hazardous waste.

Special Laboratory Facility Guidelines for CSL2

1. The facility should separate work spaces and desk areas.

2. Card key or equivalent locking systems are required for security.

CHEMICAL SAFETY LEVEL 3 - A Substantial Risk Facility

In addition to the standard practices, equipment, and facility guidelines and the guidelines for CSL2 laboratories, the following guidelines are recommended for CSL3 laboratories.

Special Safety Practices for CSL3

1. Work with chemicals of Hazard Class 3 or greater is performed in a chemical fume hood or other local exhaust containment equipment that is vented outside the building.

2. Access to CSL3 laboratories is restricted to authorized personnel at all times. Visitors must obtain permission from laboratory supervisors or other managers before escorted entry into laboratories. CSL3 facilities are secured at all times. High hazard chemicals are secured in locked storage cabinets when not in use.

Special Safety Equipment for CSL3

1. The laboratory is equipped with vented chemical fume hoods. Ductless fume hoods are not acceptable. The fume hood is certified to meet minimum performance standards given in ANSI Z9.5 and ASHRAE 110-1995 (20,21).

2. The laboratory has a balance within a ventilated enclosure to provide protection from vapors, fumes, dusts, or aerosols. Any in-line filters should be evaluated at least annually and replaced as needed. Used filters should be disposed of as hazardous waste.

3. Hot plates or other heating devices are spark-proof.

4. Centrifuges are equipped with rotors having sealed buckets or tube holders to contain aerosol formation in the event of a broken tube.

Special Laboratory Facility Guidelines for CSL3

1. Two well-separated exit doors should be available to the laboratory. The requirements for a second exit are described in NFPA 45 Standard (10).

2. Local exhaust ventilation is available to remove toxic vapors, fumes, dusts, or other aerosols from processes such as weighing powders, aerosol generation, etc.

CHEMICAL SAFETY LEVEL 4 - A High Risk Facility (7)

In addition to the standard practices, equipment, and facility guidelines and the guidelines for CSL2 and CSL3 laboratories, the following guidelines are also recommended for CSL4 laboratories.

Special Safety Practices for CSL4

1. Access is restricted to specially trained personnel only, is under the direct control of the supervisor, and is secured at all times. Visitors are not permitted in this laboratory. Personnel entering and leaving the laboratory must record purpose, date, and times of entry and exit in the laboratory log book. Administrative controls require that no one may work in this laboratory without a coworker present either inside or outside in the adjoining laboratory quadrant.

2. Warning signs are posted at the entrance to the laboratory and a description of work in this laboratory is posted weekly.

3. A daily safety checklist is used to ensure that all systems are in working order.

4. Work with materials of Hazard Class 3 or greater in any category is performed in a vented chemical fume hood or glove box.

5. Surfaces or bench tops on which high hazard chemicals are handled must be protected from contamination by using chemically-resistant trays or pans, and/or disposable absorbent paper liners. Work surfaces where high hazard chemicals are used used are decontaminated daily. All used absorbent bench top liners and decontamination materials shall be disposed of as hazardous waste.

6. Special protective clothing is required, including a full suit, head covering, gloves, boots, and foot coverings. Personal clothing is removed and stored in a locker in the dressing room, and the protective disposal clothing is donned.

7. All laboratory personnel are trained in the use of special protective equipment and procedures. Training records are maintained.

Special Safety Equipment for CSL4

1. The laboratory is equipped with stainless steel chemical fume hoods meeting standards in ANSI Z9.5 and ASHRAE 110-1995 (20,21). The hood is provided with removable glove ports and is equipped with a pressure differential safety sensor, which sounds an alarm if the hood exhaust malfunctions.

2. The laboratory is equipped with stainless steel glove boxes which are gas-tight and operate under negative pressure. Glove boxes meet standards in ANSI Z9.5 (20). Incoming air is HEPA-filtered and the exhaust side contains dual HEPA filters to filter the air before it enters the main ventilation exhaust. Glove boxes are grounded electrically, and each glove box has a built-in fire extinguisher so that it can be discharged directly into the glove box in the event of a fire. A safety switch for the glove boxes shuts off all electrical power in the event of loss of exhaust in the main system. Glove boxes may be equipped with a hazardous gas monitor alarm that continuously monitors for combustible or toxic gas or fumes.

3. Refrigerators or freezers used for storage of chemicals or samples containing chemicals are lockable.

4. Chemical storage cabinets where highly toxic materials are stored shall be locked. High hazard materials are stored in labeled secondary containers.

5. Bench surfaces are stainless steel; all walls, floors, and ceilings are sealed.

Special Laboratory Facility Guidelines for CSL4

1. The ventilation system for this laboratory is an independent system, separate from the rest of the building laboratory exhaust ventilation system. Exhaust air from the laboratory is passed through a high efficiency particulate air (HEPA) filter and a carbon adsorption (CA) filter. HEPA-CA filter units are the bag-in/bag-out type and can be maintained and replaced without personnel being exposed or the surrounding environment being contaminated.

2. This facility consists of three main areas: dressing room, anteroom and main laboratory. It requires a separate entry into a changing rooms equipped with showers. Passage through the shower area is from the “clean” side to an ante room on the “dirty” side and then into the laboratory. The dressing room provides access to the laboratory, storage for disposable laboratory clothes, and facilities for removing and storing street clothes. Fiber barrels for containment of used disposable laboratory clothing are located in the anteroom. There is a shower facility between the dressing room and anteroom. A toilet is located off the anteroom.

3. Large observation windows permit observation of work within the laboratory.

4. Depending on the hazards of the operations, airline-supplied suits may be required to prevent personnel exposure. The supply air must be tested periodically to ensure it meets ANSI Grade D breathing air quality. The use of this air supply system requires a back-up air supply that automatically activates in the event of the failure of the primary system. An alarm system must also be available to signal the failure of the primary system. Suits must be periodically decontaminated and checked for holes and tears.

5. A lab-to-lab intercom system provides communication into the laboratory.

6. All materials enter and exit the laboratory through a pass-through compartment. Large pieces of equipment are transported through the anteroom emergency exit.

7. Manifolds outside of the laboratory provide supply lines carrying reagent gases from cylinders into the laboratory.

8. All sinks are foot-actuated or equipped with automatic faucets to minimize cross-contamination.

PROPOSED METHODOLOGY FOR CLASSIFICATION OF LABORATORIES

Our proposed approach to classifying laboratories includes a workplace survey to gather information on the facility and existing engineering controls. This information will help to establish the maximum chemical safety level designation possible given the existing facility. For example, if the laboratory does not have a chemical fume hood, the highest chemical safety level that could be assigned would be CSL2. The next step in the process would be to review the laboratory’s chemical inventory to identify restricted and limited quantity chemicals. For CSL2 labs, restricted chemicals include Hazard Class 4 chemicals which are not permitted except by special EHS exemption. If restricted chemicals are required to be used, standard operating procedures must be developed by the laboratory supervisor and the conditions of use specified by EHS. Standard operating procedures are then be incorporated into the lab’s Chemical Hygiene Plan and all lab personnel made familiar with the required procedures. For limited quantity chemicals, a determination would be made as to the limits on the total quantity of the chemical to be stored or used within the lab. For example, Hazard Class 3 chemicals are limited in CSL2 labs to quantitites of 1 liter or less for liquids and 0.5 kilogram or less for solid materials. However, the laboratory’s total quantity of Hazard Class 3 chemicals may be further limited if appropriate storage areas are not available.

Laboratory operations and work procedures will also be reviewed to ensure that personnel are appropriately protected and following safe procedures. For example, aerosol-generating operations are restricted to laboratories or work areas with vented chemical fume hoods or biological safety cabinets (CSL2 minimum). However, depending upon the chemicals involved, a higher-rated CSL lab may be required to safely carry out operations.

Following the initial review of laboratories within a facility, a master list of laboratories and specific processes with their respective CSL designations could be obtained. This will provide useful information for future reevaluations of the labs as well as provide specific information to the researchers as to the types of processes that can be safely conducted within their existing facilities. Reevaluation of all CSLs labs should be conducted at least annually and whenever processes or research protocols change.

CONCLUSION

The proposed system for classifying chemical safety practices in microbiological and biomedical laboratories is presented as a starting point for developing chemical safety levels. Many details must be worked out and there may be laboratories that do not seem to fit in any category. Yet this paper seeks to promote a discussion for further refinements and clearer delineations of CSLs. We hope that this system will be viewed as a positive improvement in chemical safety practices for microbiological and biomedical laboratories. The designation of a CSL provides personnel who have a need to enter the laboratory with a means to better understand the relative risks of chemical hazards in the laboratory under normal and emergency conditions.

The recent problems with Pfiesteria piscicida are also illustrative of the need for such a system (22,23,24). When the reports of laboratory workers becoming ill from exposure to the Pfiesteria were made public, there were a large number of inquiries as to what biosafety level should be used. Pfiesteria however is not an infectious disease but rather a organism which produces toxic products which likely caused the observed illness. A toxic agent has different properties from an infectious agent and presents different concerns. Control of contamination is particularly important since decontamination may be difficult. Perhaps that work with Pfiesteria should have been performed using a CSL3 classification rather than the BSL2 or BSL3 that were recommended.

The CSL system is proposed as a set of guidelines to assist laboratory workers, supervisors, managers, and safety professionals in improving chemical safety in microbiological and biomedical laboratories. These guidelines can be used to supplement and assist chemical safety programs seeking to comply with OSHA’s performance-based laboratory standard (13). The standard classification of laboratories via CSLs can be used in conjunction with other classifications, such as BSLs, radiation use, laser use, etc, to provide an overall assessment of each laboratory. This could be very useful in a laboratory registration system which could be used to give a laboratory an overall rating (Dr. Henry Mathews, CDC, personal communication). The rating can be used as a measure for justification of the need for further refinements in the laboratory. Laboratorians and safety professionals are continually trying find ways to make our workplaces safer. CSLs offer an opportunity to improve chemical safety in microbiological and biomedical laboratories by providing a clearer foundation upon which to build a better ethic for handling chemicals in these laboratories. The approach of the CSL system is to limit chemical usage and storage in laboratories not well suited for high hazard chemicals, thus reducing the risk of chemical exposure.

Further research will focus on developing and refining the CSLs described in this paper. A methodology will be developed to characterize various laboratories which will take into consideration the process involved, hazards of the chemicals in use, and exposure potential of personnel. Once the method is developed, it will be field tested to determine its validity, ease of use, and acceptance among laboratorians, supervisors, managers, and health and safety professionals. This system will be piloted in the laboratories at the Centers for Disease Control and Prevention in Atlanta, but the authors are also interested in the use of this system in other laboratories. Success in these laboratories will allow the system to be expanded to a broader audience. The authors solicit comments and suggestions to make this system as practical and useful tool as possible. Authors may be reached at the address given above or may be contacted via the internet at rhh2@cdc.gov (Robert Hill) or jag9@cdc.gov (Jean Gaunce).

ACKNOWLEDGMENTS

The authors wished to thank Dr. Jonathan Richmond for his support and encouragement in developing this work. We also gratefully thank those in the Office of Health and Safety who provided valuable suggestions and helpful criticisms - Dr. David Taylor, Ms. Rebecca West, Dr. Henry Mathews, Ms. Cheryl Connell, Dr. Peg Tipple, and Mr. Mark Hemphill.

REFERENCES

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3. University of Nebraska. Radiation Safety Manual. Appendix D. Radionuclide Laboratory Classification. (http://www.unl.edu/environ/radsaf/labclass.htm). 1999.

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7.Myers, G.L.; Liddle, J.A.; Hill, R.H. Jr.; Needham, L.L. Am. Ind. Hyg. Assoc. J. , 48, 524-527.

8. Centers for Disease Control and Prevention/National Institutes of Health, Primary Containment for Biohazards: Selection, Installation, and Use of Biological Safety Cabinets, Richmond, J.Y.; McKinney, R.W. (Eds.), U.S. Government Printing Office, Washington, DC, 1995.

9. National Fire Protection Association. NFPA 30 Flammable and Combustible Liquids Code, 1996 Edition, National Fire Protection Association, Quincy, MA, 1996.

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11. National Fire Protection Association. NFPA 49 Hazardous Chemicals Data, 1994 Edition, National Fire Protection Association, Quincy, MA, 1996.

12. Occupational Safety and Health Administration. §1910.106, Flammable and combustible liquids. 29 Code of Federal Regulations, Government Institutes, Rockville, MD, 1996.

13. Occupational Safety and Health Administration. §1910.1450, Occupational exposure to hazardous chemicals in laboratories. 29 Code of Federal Regulations, Government Institutes, Rockville, MD (1996).

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15. National Toxicology Program, Annual Report on Carcinogens, 8^th ed. U.S. Department of Health and Human Services, U.S. Government Printing Office, Washington, DC.

16. International Agency for Research on Cancer. IARC Monographs on the Evaluation of the Carcinogenic Risks of Chemicals to Man. Vol. 1-73, World Health Organization Publications Center, Albany, NY (– ed.).

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18. Segal, E.B. Chem. Health Safety 1997, 4 (3), 33-37.

19. American National Standards Institute, American National Standard for Emergency Shower and Eyewash Equipment, ANSI Z358.1-1990, American National Standards Institute, New York, NY, 1990.

20. American National Standards Institute; American Industrial Hygiene Association. American National Standard for Laboratory Ventilation, ANSI/AIHA Z9.5-1992, American Industrial Hygiene Association, Fairfax, VA, 1992.

21. American National Standards Institute; American Society of Heating, Refrigeration, and Air Conditioning Engineers. Method of Testing Performance of Laboratory Fume Hoods (ANSI/ASHRAE 110-1995), American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Atlanta, GA (1995).

22. Glasgow, H.B.; Burkholder, J.M.; Schmechel, D.E.; Tester, P.A.; Rublee, P.A. J. Toxicol. Environ. Health 1995, 46, 501-522.

23. Centers for Disease Control and Prevention. Results of the public health response to Pfiesteria workshop - Atlanta, GA, September 29-30, 1997. MMWR 1997, 46, 951-2.

24. Brown, S.; Hales, T.; Kiefer, M.; Gittleman, J. NIOSH Health Hazard Evaluation Report, HETA 97-0327-2665, U.S. Fish and Wildlife Service, Warm Springs Regional Fisheries Center, Warm Springs, GA, NIOSH, 1997.

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Table 1

Chemical Hazard Classifications

Hazard Level

Associated Chemical Hazards

Health Hazards

Regulated, confirmed, probable, or suspected human carcinogen, mutagen, or teratogen (13,14,15,16);

Occupational exposure levels <1 mg/m³ or <10 ppm (17);

Toxicity: LD₅₀ < 50 mg/kg; LC₅₀ < 2 mg/L dust or 200 ppm vapor (5);

Flammability (11)

Extremely flammable - Flash point below 73^oF (22.8^oC) and boiling point below 100^oF;

Flammable gases and cryogenic materials;

Materials that spontaneously ignite when exposed to air;

Reactivity (11)

Can explode or decompose violently at normal temperature and pressure;

Can undergo a violent self-accelerating exothermic reaction with common materials by itself;

May be sensitive to mechanical or local thermal shock at normal temperature and pressure;

Health Hazards

Possible human carcinogen, mutagen, or teratogen (13,14,15,16);

Occupational exposure level: 10-50 ppm or 1-5 mg/m³(27);

Toxicity Level: LD₅₀ = 50 to 500 mg/kg; LC₅₀ = 2 to 20 mg/L dust or 200 to 2,000 ppm vapor (5);

Flammability (11)

Vaporizes readily and can be ignited under almost all ambient conditions;

May form explosive mixtures with or burn rapidly in air;

May burn rapidly due to self-contained oxygen;

May ignite spontaneously in air;

Flash point at or above 73^oF (22.8^oC) but less than 100^oF (37.8^oC);

Reactivity (11)

Can detonate or explode but requires a strong initiating force or confined heating before initiation;

Readily promotes oxidation with combustible materials and may cause fires;

Is sensitive to thermal or mechanical shock at elevated temperatures;

May react explosively with water without requiring heat or confinement;

Health Hazards

Not classifiable as a carcinogen, mutagen, or teratogen (13,14,15,16);

Occupational exposure limits: 5-15 mg/m³ or 50-500 ppm (17);

Toxicity Level: LD₅₀ = 500 mg/kg to 5 g/kg; LC₅₀ = 20 to 200 mg/l dust; 2,000 to 20,000 ppm vapor (5);

Flammability (11)

Must be moderately heated or exposed to relatively high temperatures for ignition to occur;

Solids which readily give off flammable vapors;

Flash point at or above 100^oF (37.8^oC) but less than 200^oF (93.4^oC);

Reactivity (11)

Normally unstable and readily undergoes violent change at elevated temperatures and pressures but does not detonate;

May undergo chemical change with rapid release of energy at normal temperature and pressure;

May react violently with water;

Forms potentially explosive mixtures with water;

Health Hazards

Evidence of non-carcinogenicity or not suspected as a human carcinogen (14,16), Not suspected as a human mutagen, or teratogen;

Occupational exposure limit: >15 mg/m³ or 500ppm (17);

Toxicity Level: LD₅₀ > 5g/kg; LC₅₀ > 200 mg/L dust or > 20,000 ppm vapor (5);

Flammability (11)

Slightly combustible - Must be preheated for ignition to occur; will burn in air when exposed at 1500^oF (815.5^oC) for 5 minutes; or flash point at or above 200^oF (93.4^oC);

Noncombustible - Will not burn, exhibit a flash point, or burn in air when exposed at 1500^oF (815.5^oC) for 5 minutes.;

Reactivity (11)

Normally stable material which can become unstable at high temperature and pressure;

Normally stable material which does not react with water;

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Table 2

High Risk Chemicals [Hazard Class 4] - Examples

[Restricted List for CSL2 Labs]

Regulated, known or probable human carcinogens, mutagens, or