Fumigation

introduction, definition , solutions and different methods of fumigation

1. F umigation Arya S.S CRRI

2. Introduction  Surgical site infections (SSIs) are the second most common cause of hospital acquired infections.  The source of SSIs may be endogenous or exogenous, which includes surgical personnel ,the operating room environment (including air), and tools, instruments, and materials brought to the sterile field during an operation.  By maintaining sterile environment in operation theatre we can control major part of exogenous infections.  Fumigation is the process by which we can sterilize the enclosed area by injecting the chemical which will kill or destroy microbes present in the air.

3. Fumigation  Fumigation is a process of gaseous sterilisation which is used for killing of micro-organisms and prevention of microbial growth in air, surface of wall or floor.  It is generally used in the pharmaceuticals, operation theatres, hospitals, hotels and offices and wherever required.  Method of fumigation completely fills an area with gaseous fumigants to suffocate or poison the microbes & pests within.

4. Widely used fumigants include: Formaldehyde phosphine 1,3-dichloropropene chloropicrin methyl isocyanate hydrogen cyanide sulfuryl fluoride Iodoform Methyl bromide Fumigation equipment

5. Formaldehyde  A gas at room temperature, formaldehyde is colorless and has a characteristic pungent, irritating odor.  When dissolved in water, formaldehyde forms a hydrate methanediol.  A saturated water solution, that contains about 40% formaldehyde by volume or 37% by mass, is called "100% formalin".  A typical commercial grade formalin may contain 10– 12% methanol added to suppress oxidation and polymerization.

6.  Formaldehyde at approximately 5% in a solution with water is used as a fumigant and disinfectant in hospitals.  Formoldehyde kills microbes  In order to be effective, the gas has to dissolve in the film of moisture surrounding the bacteria, for this reason relative humidities in the order of 75% RH and temperature above 22°C. Formaldehyde molecule

7. Methods  Electric Boiler Fumigation Method: For Each 1000 cu.ft 500ml of formaldehyde added in 1000ml of water in an electric boiler. Switch on the boiler, leave the room and seal the door. After 45 minutes switch off the boiler without entering in to the room.  Potassium Permanganate Method: For every 1000 cubic feet add 450gm of Potassium permanganate (KMnO4) to 500 ml of formaldehyde. Take about 5 to 8 bowels with equally divided parts of formaldehyde and add equally divided KMnO4 to each bowel. This will cause auto boiling and generate fume.

8. Neutralisation  After the initiation of formaldehyde vapour immediately leave the room and seal it for at least 48 hours  Neutralise residual formalin gas with Ammonia by exposing 250ml of Ammonia per litre of Formaldehyde used.  Place the Ammonia solution in the centre of the room and leave it for 3 hours to neutralise formalin vapour.

9. Quantity Example  Operation Theatre volume= L× W ×H=20×15×10= 3000 cubicfeet  Formaldehyde required for fumigation=500ml for 1000 cubic feet  So 1500ml Formaldehyde required  Ammonia Required for neutralisation=150ml of 10% ammonia for 500ml of formaldehyde  So 450ml of 10% ammonia required

10. Phosphine  Phosphine is the compound with the chemical formula PH3.  It is a colorless, flammable, toxic gas. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor.  Phosphine-producing materials have become the predominant fumigants used for the fumigation of OT .  I t i s a v a ilabl e in s ol i d formulat i o ns of aluminum phosphide or magnesium phosphide.

11.  When exposed to heat and moisture the formulations release phosphine, a highly toxic gas.  The time required for release of phosphine will vary with temperature and formulation.  Phosphine is very toxic to all forms of animal life, hence exposure of human beings even to small amounts should be avoided.  Phosphine can be produced via tablets or phosphine producing equipment.

12. Phosphine producing Equipment Phosphine Tablets * Phosphine i s ge n e raly used for f u m i g ati n g huge quantity of food grain than operation theatre

13. 1,3-dichloropropene & chloropicrin  1 , 3 - dich l o r o pr o p e n e & ch l o r op i crin i s gen e r a l y used a s so i l fumigants only chem i cal i n the Methyl isocyanate  M e t hyl is o c y an a te i s a n i n t e rme d i ate production of carbamate pesticides.  Methyl isocyanate fumes can also be used as a fumigant.  Methyl isocyanate (MIC) is extremely toxic.  It was the principal toxin involved in the Bhopal disaster.  Even small quantity is extremely toxic to humans, so currently not used in fumigation.

14. Methyl Bromide w i d e l y used fum i g a nt for  Me t h y l Bro m i d e i s most quarantine purposes  It is a preferred fumigant because of its good penetrating ability, rapid action, high toxicity to a broad spectrum of micro organisms and pests.  The effectiveness of methyl bromide is based on the following: Dosage of the fumigant Duration of exposure Temperature

15.  When fumigation is carried out with Methyl Bromide fumigant, there will not be any residual issues as aeration can be carried out easily.  Methyl Bromide fumigation can be carried out at the dosage that varies between 32 grams/ m3 and 80 grams/ m3 as per the requirements.  Methyl bromide is considered to be a significant ozone depleting substance (ODS) by atmospheric scientists.  Methyl bromide is readily photolyzed in the atmosphere to release elemental bromine, which is far more destructive to stratospheric ozone than chlorine.

16. Preparation for fumigation  First the area intended to be fumigated is usually covered to create a sealed environment.  The fumigant is released into the space to be fumigated.  The space is held for a set period while the fumigant gas percolates through the space and acts on and kills any infestation.  The space is neutralised & ventilated so that the poisonous gases are allowed to escape from the space, and render it safe for humans to enter.

17.  Windows, doors should be closed. AC and AHU should be switched off before starting fumigation.  Area under fumigation, do not enter status label should be displayed on either side of the entrance.  Fu m i ga n t s ar e i r r i t a ting an d t o x i c t o human e y e , nose and throat. Therefore use of nose mask and goggles while doing fumigation is advisable.

18.  Under certain conditions formaldehyde can react with hydrochloric acid and chlorine containing disinfectants such as hypochlorites to form chloromethyl a potential lung carcinogen .  HCl and chlorine containing disinfectants must therefore be removed from areas before fumigation.  Check levels of residual fumigant in the room with suitable air monitoring equipment(formaldameter or air sampling tubes).  The procedure is best carried out overnight.

19.  After a pe r i od of n ot les s t h a n 12 hours the r o om must be well ventilated.  OT is usable only when the level of formaldehyde is less than 2ppm. Formaldemeter

20. Personal care while Fumigation  Adequa t e care must b e taken b y w e a r i ng c a p, mask,foot cover, spectacles.  Formaldehyde i s i r r it ant to eye & nos e ; an d i t h as been recognized as potential carcinogen.  Immediately leave the room after the initiation of fumigants.  So the fumigating employee must be provided with personal protective equipment.

21. Advantages of Fumigation  Fu m i ga n t s ar e t o x i c t o al l fo r ms of l i f e . T h ere f or e , i t is possible to control all life stages of Micro organisms.  Fu m i gati o n is oft e n the q u i cke s t wa y of con t r o llin g an infestation, saving time and money.  Fu m i ga n t s can reach wher e sp r a y s , d u s ts , aeroso l s etc cannot reach.  Reduced residue problems in treated areas.  Fu m i ga n t s ar e used wher e s tanda r d s c al l for " z e ro Microbial tolerance" in products or living environments.

22. Disadvantages of Fumigation ¤ Generally Formaldehyde is used for OT fumigation.  Based on the available evidence in OSHA’s record on Formaldehyde, it determines formaldehyde as isgenotoxic, showing properties of both a cancer initiator and promoter.  In humans formaldehyde exposure has been associated with cancers of the lung, nasopharynx and nasal passages.  Symptoms of excessive exposure include respiratory irritation, itchy eyes, runny or stuffy nose, sore throat and headache.

23. Formaldehyde allergy  Formalde h y d e a l l ergy s y mp t oms i ncl u de redness, burning sensation, scaling and irritation of skin.  Eye contact can cause pain, burning sensation, blurred vision and excessive tearing.  Further, formaldehyde can cause difficulty breathing in allergic individuals, particularly those with asthma or another respiratory condition.

24. Alternative methods  Fumigation is an age old process of sterilisation , of the environment, may be a sick room or operation theatres.  In spite of brief stay of patients in the operation theatre, the environment of operation theatre plays a great role in the onset and spread of infections.  But every hospital should pay good attention in proper maintenance of air conditioning plants, ventilator systems, and to have greater control on mechanisms and personnel involved in disinfection.

25.  Many believe that routine Microbiological monitoring is most essential but in reality it is not practicable.  Special air flow pattern (the air flow pattern is such that filtered and purified air circulates and contaminated air is removed continuously).  There should be restriction of personnel traffic, closing of OT doors and a good ventilation system.  Standard cleaning, disinfection with appropriate chemical agents, good theatre practice, discipline, can provide a microbiologically safe environment.

26.  Fumigation is obsolete in many developed nations in view of toxic nature of Formalin.  Several new safe chemicals are emerging but constrains of economy limit the use and several hours of closure of operation theatres can be curtailed as with Fumigation.  Aldehydes are potentially carcinogenic and it is therefore recommended that other agents such as hydrogen peroxide, hydrogen peroxide with silver nitrate, peracitic acid and other chemical compounds of formaldehyde should be used in place of the currently prevalent practice of using formaldehyde.

27.  These agents are dispersed with the aid of a fogger-like device inside the theatre environment.  The contact time is about an hour and the theatre can be used immediately after the contact time. Fogging method