Question

4a. Explain which biosafety cabinet is most suitable for a procedure that involves animal cells and flammable solvents.

b. A vessel disinfection procedure must be modified to sterilize the vessel. What types of changes in the procedure might be proposed?

c. Explain why TLV-TWA values cannot be used as a measure of relative toxicity of chemicals. 4d. Explain why maintaining a work environment at chemical concentrations below the TLV-TWA does not guarantee prevention of any adverse health effects for workers.

Answer 1

b.) the following are the procedures :

Antisepsis: A process involving the destruction or inhibition of mico-organisms in living tissue thereby limiting or preventing the harmful effects of infection.

Antiseptic: Typically an antiseptic is a chemical agent that is applied to living tissue to kill microbes. Note that not all disinfectants are antiseptics because an antiseptic additionally must not be so harsh that it damages living tissue. Antiseptics are less toxic than disinfectants used on inanimate objects. Due to the lower toxicity, antiseptics can be less active in the destruction of normal and any pathogenic flora present.

Autoclave: An autoclave is a high pressure device used to allow the application of moist heat above the normal-atmosphere boiling point of water.

Biocidal: Active substances and preparations which serve to repel, render harmless or destroy chemically or biologically harmful organisms.

Biocide: Substance or chemical that kills biological organisms.

Decontamination: The killing of organisms or removal of contamination after use, with no quantitative implication, generally referring to procedures for making items safe before disposal.

Disinfectant: A germicide that inactivates virtually all recognized pathogenic microorganisms but not necessarily all microbial forms. They may not be effective against bacterial spores.

Disinfection: A procedure of treatment that eliminates many or all pathogenic microorganisms with the exception of bacterial spores.

Germicide: An agent that destroys microorganisms, particularly pathogenic microorganisms.

Pathogenic: A microbe or other organism that causes disease.

Sanitization: The process of reducing microbial contamination to an acceptable “safe” level. The process of cleaning objects without necessarily going through sterilization.

Steam Sterilization: Autoclave, the process of sterilization by the use of heated steam under pressure to kill vegetative microorganisms and directly exposed spores. Common temperature and pressure for being effective is 121°C (250°F) at 15 psi (pounds per square inch) over pressure for 15 minutes. Special cases may require a variation of the steam temperature and pressure used.

Sterilization: The complete elimination or destruction of all forms of life by a chemical or physical means. This is an absolute not a relative term.

Sterilization

1. Steam Autoclave:

Always consult with the Autoclave Manufacturer and/or Operators Manual for proper temperature, pressure, and time because these may be different that what is specified in this document.

Only autoclaves that have been registered with EH&S may be used for the disinfection of pathogenic or “suspect” infectious materials. Each of these autoclaves has a white “EH&S” sticker on it with an assigned number. You must contact EH&S if you want to use an autoclave that has not previously been registered, assigned a number, and has not had a spore test performed within 90 days and maintenance service performed within 6 months.

The CU Biological Laboratory Waste Management Disposal Policy & Procedure requires that if an autoclave is used for the sterilization of pathogenic cultures or “suspect” infectious materials, then a commercially available Bacillus stearothermophilus or Bacillus subtilis var. niger test strips must be used at least once every 90 days to validate and document the killing efficiency of the autoclave. One copy of the test results must be posted on or near the autoclave and another copy sent to EH&S. In addition, this autoclave must be checked by an authorized service provider at least every 6 months (preferably every 60-90 days) to assure proper function, i.e., preventative maintenance, temperature calibration, and verification of adequate disinfection (if Lab does not perform Bacillus test). One copy of the current preventive maintenance record must be posted on or near the autoclave and another copy sent to EH&S.

EH&S must be notified if any EH&S registered autoclave has been removed from service, or does not pass either the spore test or maintenance service. A sign must be posted on the autoclave to note “Autoclave Out Of Service”. Do not resume using autoclave until it has been successfully repaired to meet all manufacturers’ requirements for effective disinfection. Please inform EH&S when there are changes in the autoclaves and/or their uses.

Autoclaving at a temperature of 121oC (250?F), at 15 to 20 psi is one of the most convenient and effective means of sterilization available. The time is measured after the temperature of the material being sterilized reaches 121ºC (250ºF). Care must be taken to ensure that the steam can circulate around articles in order to provide even heat distribution. The success of the sterilization is very time-dependent in liquid media, with large volumes requiring longer periods of time to reach the effective temperature within the media itself. Additionally, there should be no void spaces in the load that could insulate against the steam – this condition could prevent the transference of heat to the vessels resulting in no sterilization of the contents.

In dry loads small amounts of water should be included inside the autoclave bag to ensure sufficient moisture content within the load to allow for heat transference and distribution. Autoclave tape can be used for routine runs where glassware or sterile media are prepared before use.

a) the following are the Biological Safety Cabinets is most suitable for a procedure that involves animal cells and flammable solvents are as follows.

Class II BSCs provide an effective partial barrier system for the safe manipulation of low-, moderate-, and high-risk microorganisms. Class II cabinets, which are the most frequently used in research and clinical laboratories, are divided into four types (Types A1, A2, B1 and B2).

Class III BSC is a totally enclosed, gas-tight ventilated cabinet, and provides the highest level of personnel, environmental and product protection. Operations within a Class III BSC are conducted through attached rubber gloves.

c) TLV - TWA  are not a standards setting body. TLVs and TWA are health-based values and are not intended to be used as legal standards.since these limits are only for 8 hrs/day or 40 hrs/week these limits are not considered because workers should expose to the work environment for continuously .