Sterilization formaldehyde

Line S.J. Pickerell J.K. (1973) Testing a steam-formaldehyde sterilizer for gas penetration efficiency. J Clin Pathol, 26, 716-720. 

Hoxey EV, Soper CJ, Davies DJG. 1985. Biological indicators for low temperature steam formaldehyde sterilization Effect of defined media on sporulation, germination index and moist heat resistance at 110 degrees C of bacillus strains. J Appl Bacteriol 58 207-214. 

Figure 2. TNT degradation in soil by co-cultures. A (control), no inoculum, sterile (autoclaved) soil, 2% starch added B (control), 10% inoculum of white colonies killed by 10% formaldehyde, sterile soil, 2% starch added C, 10% inoculum of white colonies, sterile soil D (control), no inoculum, non-sterile soil, 2% starch added E, 10% inoculum of clear colonies, sterile soil F, 10% inoculum of clear colonies, sterile soil, 2% starch added C (dashed line), 10% inoculum of white colonies, sterile soil, 2% starch added.

Formaldehyde is employed as a disinfectant in both solution and gaseous forms for a wide variety of miscellaneous purposes. Common uses include disinfection of sickrooms by sprinkling with 2 per cent formaldehyde sterilization of surgical instruments by boiling 2 10 minutes w ith 2 to 4 per cent solution, destruction of anthrax bacteria in imported bristles b ... 

Chemical disinfectants are limited in their use as air sterilants because of their irritant properties when sprayed. However, some success has been achieved with atomized propylene glycol at a concentration of 0.05-0.5 mgH and quaternary ammonium compounds (QACs) at 0.075% m be used. For areas which can be effectively sealed off for fumigation purposes, formaldehyde gas at a concentration of 1-2 mg H of air at a relative humidity of 80-90% is effective. 

Closure liners of pulpboard or cork, unless specially treated with a preservative, foil or wax coating, are often a source of mould contamination for liquid or semi-solid products. A closure with a plastic flowed-in linear is less prone to introduce or support microbial growth than one stuck in with an adhesive, particularly if the latter is based on a natural product such as casein. If required, closures can be sterilized by either formaldehyde or ethylene oxide gas. 

The British Pharmacopoeia (1993) recognizes five methods for the sterilization of pharmaceutical products. These are (i) dry heat (ii) heating in an autoclave (steam sterilization) (iii) filtration (iv) ethylene oxide gas and (v) gamma or electron radiation. In addition, other approaches involving steam and formaldehyde and ultraviolet (UV) light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability... 

Formaldehyde gas for use in sterilization is produced by heating formalin (37% wA aqueous solution of formaldehyde) to a temperature of 70-75°C with steam, leading to the proeess known as LTSF. Formaldehyde has a similar toxicity to ethylene oxide and although absorption to materials appears to be lower similar desorption routines are leeommended. A major disadvantage of formaldehyde is low penetrating power and this limits the packaging materials that eanbe employed to principally paper and eotton fabrie. 

Low-temperature steam and formaldehyde Gas concentration 15-100 mgl" Steam admission to 73°C 40-180min sterilizing time depending on type of process... 

Low-temperature steam with formaldehyde is of value in the disinfection/sterilization of some heat-sensitive materials (see also Chapter 20). 

Low temperature steam and formaldehyde Reactive chemical Indicator paper impregnated with a formaldehyde-, steam- and temperature-sensitive reactive chemical which changes colour during the sterilization process Gas concentration, temperature, time (selected cycles)... 

Sterilization by irradiation was introduced by mid-fifties. In about 20 years, it was fully operational. When compared with the traditional methods of sterilization such as using formaldehyde, ethylene oxide (a toxic gas), or heating in an autoclave, several advantages of irradiation may be noted (Artandi, 1977) ... 

The toxoid is then prepared by treating the active toxin produced with formaldehyde. The product is normally sold as a sterile aqueous preparation. Tetanus vaccine production follows a similar approach. Clostridium tetani is cultured in appropriate media. The toxin is recovered and inactivated by formaldehyde treatment. Again, it is usually marketed as a sterile aqueous-based product. 

Nakahari [2.11] describes, on the basis of his experience with VHP , the advantages of this process a short sterilization time at room temperature, the possibility to update existing plants, VHP does not - compared with ethylenoxide and formaldehyde - affect the health of the operators and can be decomposed to water and 02 without contaminating the atmosphere. 

Materials Required Standard chlortertracyline sterilized media (as described above) 1 L authentic and pure strain of microorganism Staphylococcus aureus (NCTC 6571) formaldehyde solution (34-37% w/v) 10 ml matched identical test tubes 20 ... 

Formaldehyde and glutaraldehyde are used for disinfection or sterilization of instruments such as fiberoptic endoscopes, respiratory therapy equipment, hemodialyzers, and dental handpieces that cannot withstand exposure to the high temperatures of steam sterilization. They are not corrosive for metal, plastic, or rubber. These agents have a broad spectrum of activity against microorganisms and viruses. They act by alkylation of chemical groups in proteins and nucleic acids. Failures of disinfection or steri... 

Alkylating agents Disrupt structures of proteins and nucleic acid Formaldehyde is used to inactivate viruses without destroying antigenic properties, glutaraldehyde is used to sterilize equipment, betapropiolactone is used to destroy hepatitis viruses, and ethylene oxide to sterilize objects that would be harmed by elevated temperatures... 

Chemical (vapor phase) Ethylene oxide Propylene oxide Formaldehyde (3 - Propiolactone Disinfection temperature Ethylene oxide also used as sterilizing agent Possible carcinogenic activity of p-propiolactone... 

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