BBP - Appendix 1: Aerosols, Respiratory Protection, and Biological Safety Cabinets

MSDSs

Bloodborne Pathogens Program

Appendix 1: Aerosols, Respiratory Protection, and Biological Safety Cabinets

The OSHA standard requires that all procedures involving blood or other potentially infectious materials shall be performed in such a manner as to minimize splashing, spraying, spattering, and generation of droplets of those substances. This requirement decreases the chances of direct employee exposure and reduces contamination of surfaces.

OSHA has also reviewed whether aerosols require control measures. Aerosols are solid or liquid particles, ranging in size from submicrometer to multi-micrometer, that are suspended in a gas (the gas could be air). The suspension can last from a few seconds to a day or more. Aerosols of blood can be generated by a number of processes in healthcare and research settings. Sources are surgical power tools, removal of rubber tops from evacuated blood collection tubes, blood spills, and automatic pipetting instruments. Concerns have been raised about the generation of aerosols during centrifugation.

There is disagrement over whether respiratory protection should be used to protect against aerosol inhalation, and collateral questions about critical concentration values and monitoring. Some investigators have suggested that airborne transmission may exist, while CDC and NIOSH have stated that there are no cases traceable to airborne transmission. OSHA recognizes that the matter requires further study and has referred the matter to NIOSH. In the absence of sufficient information, OSHA has not required employers to control exposures to aerosols.

There is a hierarchy of controls to prevent exposure that must be implemented, beginning with universal precautions and including engineering controls and work practices. These should be implemented before relying on personal protective equipment such as respirators.

University policy states that human blood, blood products, and other potentially infectious materials are to be handled at Biosafety Level 2 (BL2) as defined in the CDC/NIH publication Biosafety in Microbiological and Biomedical Laboratories. Under BL2, biological safety cabinets or other appropriate personal protective or physical containment devices are to be used whenever procedures with a high potential for creating infectious aerosols are conducted. These procedures may include, but are not limited to, centrifuging, grinding, blending, vigorous shaking or mixing, sonic disruption, and opening containers of infectious materials whose internal pressures may be different from ambient pressures.

Materials may be centrifuged in the open laboratory if sealed rotor heads or centrifuge safety cups are used and if these rotors or safety cups are opened only in a biological safety cabinet or other appropriate physical containment devices such as chemical fume hoods..

Other physical containment devices could include chemical fume hoods. Care should always be taken to ensure that centrifugation or other procedures inside a hood or safety cabinet do not interfere with the airflow characteristics of the device, thereby increasing the potential for material to be carried out of the device.

Bench-top shields may be effective in protecting against splashing, spraying, spattering, and generation of droplets. Working in a chemical fume hood may also be effective provided the protective windows are manipulated both to maintain proper airflow and provide a physical barrier.

External ORS Links: Northwestern Home | Vice President for Research | Big 10 EH&S Links | Risk Management | Employee Safety Handbook

ORS - Evanston • 2145 Sheridan Road • Tech NG71 • Evanston, IL 60208
ORS - Chicago • 303 E. Chicago Avenue • Ward B106 W223 • Chicago, IL 60611
Phone 847/491-5581 or 312/503-8300 • FAX 847/467-2797 or 312/503-0547
e-mail researchsafety@northwestern.edu
Last Revision 05/16/2007
© 2007 Northwestern University. World Wide Web Disclaimer and University Policy Statements.