INTRODUCTION TO FUMIGATION AND DISINFECTION
A Practical Training Lecture in Environmental Management and Pollution Control.
ENGR. C. J. NWAOGWUGWU,MNSE
MD/CEO MACJAMES GLOBAL RESOURCES LIMITED
A) Fumigation is a method of pest control that can effectively eliminate pests and vectors from homes, agricultural commodities, and the environment by using gas, liquid or solid sublimable substances. This should follow established practices and procedure. A fumigation that is conducted improperly will not kill the pests. Such fumigations are meaningless from the environmental point of view and they may be hazardous to human and other economic plants and animals. Therefore, Fumigation is intended to eliminate 100 percent of the target pests and vectors in the target environment with no harm to humans, if possible.
B) Fumigation is a technique that effectively eliminates a range of insects and pests. Fumigation is a technique that employs various chemicals (fumigants) to eliminate pests and insects from homes, buildings and processed goods. The operation is hazardous and all fumigants are harmful to humans to some degree. According to Environmental Health Researchers, prevention is better than cure; when it comes to pests control and a combination of sanitation, mechanical controls and the use of harmless inert compounds will prove safer and more viable alternatives to fumigation.
1.2 TYPES OF FUMIGATION
1.2.1 Gas Fumigation
Gas fumigation employs fumigants in their gaseous states for pest control. According to "Clinical Environmental Health and Toxic Exposures," gas fumigation is performed within enclosed chambers or by enclosing a space with a gas-proof covering. This method of fumigation, called space fumigation, ensures toxic fumigants are not dispersed to the external environment. Methyl bromide (banned) is a gaseous fumigant that is used to control rodents, termites, insects, nematodes and weeds. Sulfuryl fluoride is a gas fumigant that is used to control pests in cereal grains, tree nuts and dry fruits. Carbon dioxide is more harmless gas for confined space fumigation. Gas fumigation must only be attempted after an area is cleared of humans and animals.
1.2.2 Solid Fumigation
Solid fumigation systems and techniques employ solid fumigants for pest control. According to M.R. Ghosh in the book "Concepts of Insect Control," solid fumigation is carried out by sprinkling tablets, powders or pellets of measured quantities of fumigants. According to the Wood Center, solid fumigants are typically easier to use and safer than gaseous fumigants and are less harmful to the environment. However, according to Environmental Health Researchers, solid fumigants are associated with numerous health concerns. Aluminum phosphide is a solid fumigant that eliminates pests and insects in all stages of development (eggs, larvae, pupae and adults). It is typically used for pest control in flour, tea, cotton, and grain in storage. Calcium cyanide is a solid fumigant that reacts with water vapor to form hydrogen cyanide. It effectively eliminates a wide range of pests.
1.2.3 Liquid Fumigation
Liquid fumigation employs liquid fumigants for mold, pests and insects. Liquid fumigation is carried out by sprayers, which disperse large quantities of liquid over a desired or targeted area. Most liquid fumigants are toxic to humans, flammable and volatile. According to Timothy J. Gibb and C. Y. Oseto in the book "Arthropod Collection and Identification," liquid fumigation acts faster than solid fumigation. Liquid fumigation is safest when performed outdoors or within an enclosed fumigation chamber. Examples of liquid fumigants include carbon disulfide, ethyl acetate, chloroform, carbon tetrachloride, sulfuryl fluoride, ethylene dichloride and methyl bromide, and other liquid pesticides mixtures.
1.3 PRINCIPLES OF FUMIGATIONS
Basic knowledge that must be understood prior to start of fumigations is as listed.
1.3.1 Sealed Enclosures
During a fumigation, the enclosure must be completely sealed otherwise the fumigant used will leak causing the fumigation not to kill insects and may be harmful to any person. Stack fumigation under tarpaulin sheet should be performed on polished concrete floor. The tarp must be in good condition and thick enough to hold the fumigant. Stakes for anchoring the sheet to concrete floor should meet the standard of proper size which is usually four inches in diameter. The stakes must be over-lapping position on the tarp around the stack. For cargo container fumigation, the rubber sealing of its door must not be torn on any part and the rubber not expired too. Barge fumigation, if the barge is all top opened; the barge is usually covered with tarp. The tarp should be sealed with very good masking tape; otherwise it may longer not fix to the barge hold edge. So far, other temporary enclosures should have very good seal at all possible leaks or vents as mentioned before.
Dosage is a given quantity of a fumigant to be applied. Methyl bromide may be applied at different dosages such as 2 Ibs (pounds) per one thousand cubic feet for common stored insects while optimum dosage for Kahpra beetle, Trogoderma granarium is 5 Ibs per one thousand cubic feet. For phosphine gas, the amount of fumigant given by number of pellets, tablets, sarchets, plates and strips which each can release a definite quantity of phosphine. In general, one pellet can release PH3 0.2 gram while one tablet releases 1 gram. However, good fumigator should follow recommended dosage schedule so as to apply the proper amount of fumigant at a time.
Dosage Schedules: To be effective, the fumigant must be applied in sufficient quantity. The correct amount depends on published fumigation schedules that are applicable to the infested commodity, pest, temperature, and certain other considerations. Failure to follow the specifications outlined in the schedules will result in faulty fumigation treatments.
Concentration is the amount of a fumigant under fumigation period. The concentration of the fumigant can be measured by the thermal conductivity or Fumiscope, Kitagawa precision concentration detector tube and Toka concentration meter. The concentration under fumigation may be-varied according to leak and sorption. Even lethal concentration throughout the enclosure is needed for good fumigation. If not, pests are not killed completely and may cause pest resistant to the fumigant in not very long future.
1.3.4 Fumigation Period
Fumigation period means the exposure period plus degas or aeration period. When the exposure period is ended the treated commodity or environment should be left aerated for a certain time. Then the concentration inside the environment will be detected to ensure that the fumigant left is not harmful to any person. If so, the fumigation period is over.
Before a constant concentration of the fumigant can be maintained the sorptive capacity of the environment under fumigation must be satisfied. It varied considerably with the environment being treated. Sorption includes the terms adsorption, absorption, desorption and chemisorption.
Adsorption is concerned with the loss of fumigant due to adhesion of impingement of the gas molecules to the surface of the materials under treatment.
Absorption is concerned with loss of gas within the commodity due to capillary forces.
Chemisorption is a chemical reaction that takes place with a gas and commodity. The process is irreversible. When chemisorption occurs, residues are formed. These residues are considered harmful in edible products.
Desorption is the result of absorbed and adsorbed gas molecules. Desorption time varies with the commodities and conditions, but it can be complete.
1.4 FUMIGATION PREPARATION
1.4.1 The day before the fumigation
- Water the soil up to 18 inches from the outer walls of your home to protect plants and shrubs.
- Cut back foliage, shrubbery and landscaping at least 18 inches from the structure to allow room
for the tarps.
- Remember to make arrangements for overnight accommodations for you and your pets, as your home may be under fumigation for 24 to 48 hours.
- Please keep in mind the fumigation may need to be rescheduled if the weather is uncooperative. High winds and rain may hinder fumigation and cause potential danger to fumigators.
1.4.2 The day of the fumigation
- Remove all plants from your home, including those on outdoor patios.
- Evacuate all people and pets from the structure.
- Remove mattresses completely enveloped in plastic, such as baby mattresses with waterproof covers, or remove the covers.
- Remove or double-bag any food, feed, drugs, and medicines in special Nylofume bags that we provide. You do not need to bag or remove items in plastic, glass or metal bottles, cans or jars with the original manufacturer's airtight seal intact. (Can be done day before as well.)
- Seal the Nylofume bags one at a time by twisting the tops, folding down and sealing with tap, twist ties, string or rubber bands. DO NOT TIE BAGS IN A KNOT.
- Double-bag cold and frozen food and leave them in the refrigerator or freezer. Remove shelves from the refrigerator and freezer to make it easier to stack the bags inside.
- Be sure to double bag anything that will be ingested (medicine, spices, etc.).
1.4.3 After the fumigation
- It is necessary to wash dishes, linens clothing, etc., as gas and will dissipate from the structure.
- Allow ventilation of the enclosed spaces
- Remember, once your fumigation is complete, all target pests in your structure may have been eliminated.
- Remove coverings and return everything to normal their places.
2.0 INTRODUCTION TO DISINFECTION
2.1 GENERAL DEFINITIONS.
2.1.1 Disinfection is the destruction of pathogenic and other kinds of microorganisms by physical or chemical means.
2.1.2 Disinfection is the killing, inhibition, or removal of microorganisms that cause disease by using disinfectants. Disinfectants are chemical substances used to destroy viruses and microbes (germs), such as bacteria, fungi, protozoa, etc.
2.2 DEFINITION OF TERMS
2.2.1 Antimicrobial agents may have one of two effects: they may inhibit microbes or kill them. Agents that inhibit microbes are said to be STATIC. Agents that kill microbes are said to be CIDAL.
These terms are used to describe the action of disinfectants and also antibiotics. For example, phenol is germicidal whereas mercury ions are bacteriostatic: chloramphenicol is bacteriostatic and gentamicin is bactericidal. Many chemicals used in sterilisation and disinfection are cidal, killing microbes. Food preservatives, however, must not be toxic to the people who will consume them. These tend to be static agents.
Sterilization is the destruction of ALL infectious agents from an environment. This includes algae, bacteria, fungi, protozoa, viruses and other forms of microbes, leaving the environment or object sterile (free from micro organisms)
Whereas sterilization is an absolute phenomenon, the definition of disinfection is more nebulous. It refers to the removal from an environment of microbes that may cause disease (pathogens).
Antisepsis is the disinfection of living tissues; achieved through the use of antiseptics. In general, antiseptics are less harsh in their action than are disinfectants, many of which are toxic to humans.
This is another nebulous term referring to the "removal of microbes that pose a threat to the public health". It is used in the food industry and homes.
Strictly, antibiotics are substances produced by one microbe that inhibits or kills another microbe. Often the term is used more generally to include synthetic and semi-synthetic antimicrobial agents.
Antimicrobial agents are substances that inhibit or kill microbes. Often this term is used to describe synthetic antimicrobials rather than antibiotics - themselves the products of microorganisms. The terms antibiotic and antimicrobial agents are often used loose.
2.3 ELIMINATING MICROBES.
A disinfectant is a chemical or physical agent that is applied to inanimate objects to kill microbes
(a) Typically an antiseptic is a chemical agent that is applied to living tissue to kill microbes
(b) Note that not all disinfectants are antiseptics because an antiseptic additionally must not be so harsh that it damages living tissue
(c)With this constraint imposed on antiseptics, in general antiseptics are either not as cheap or not as effective at killing microbes as disinfectants
(a) Sterilization is the killing of all microorganisms in a material or on the surface of an object
(b)A surface or an object is either sterile or it is not sterile, there are no gradations in sterility
(c) Typically the last things to die when one attempts sterilization is the highly heat- (and chemical-,etc.) resistant endospores
Sanitization is the cleaning of pathogenic microorganisms from public eating utensils and objects such as that done by the kitchen of a restaurant.
2.4 KILLING MICROBES
(a) The killing of microorganisms occurs exponentially where some fraction of the living population dies per unit time
(b) "A definite proportion of the organisms die in a given time interval."
(c) "Soon the probability of finding even a single live organism becomes very small. Most laboratories say a sample is sterile if the probability is no greater than one chance in a million of finding a live organism."
2.4.2 Cleanliness effects
(a) "The fewer organisms present, the shorter the time needed to achieve sterility. Thoroughly cleaning objects before attempting to sterilize them is a practical application of this principle. Clearing objects of tissue debris and blood is also important because such organic matter impairs the effectiveness of many chemical agents."
2.4.3 Organismal differences
(a) "Microorganisms differ in their susceptibility to antimicrobial agents."
(b) Often what fails to be killed by a disinfectant are endospores though certain viruses and some vegetative bacteria are also highly resistant to disinfection
(c) Also, the same organism may differ in susceptibility depending on growth phase with actively growing organisms typically more susceptible to disinfection than not-growing cultures
2.4.4 Temperature effects
(a) Increasing temperatures increases the efficacy of most chemical antimicrobials
(b) The converse of this statement is that relatively cold temperatures result in relatively poor disinfection
2.4.5 Concentration effects
(a) Generally, the use of more disinfectant provides better killing than the use of less disinfectant
2.4.6 Bactericidal effects
(a) An antimicrobial that kills a microorganism (or, more specifically, a bacterium) is said to be bactericidal
2.4.7 Bacteriostatic effects
(a) Some antimicrobials are only bacteriostatic, including some bactericidal agents used at too-low concentrations
(b) Bacteriostatic means that the antimicrobial inhibits bacterial growth but does not kill the bacteria; consequently, removal or dilution of the antimicrobial can result in a resurgence of bacterial growth
(c) Note that sufficient, prolonged application of even bacteriostatic agents can often result in bacterial death, a consequence, for example, of extended dormancy in which cellular repair is inhibited
2.4.8 The ideal disinfectant
(a) As quoted from your text: "An ideal disinfectant should
(i) Be fast acting even in the presence of organic substances, such as those in body fluid; [resistant to inactivation]
(ii) Be effective against all types of infectious agents without destroying tissues or acting as a poison if ingested; [broadly active]
(iii) Easily penetrate material to be disinfected without damaging or discoloring the material; [not poisonous or otherwise harmful]
(iv) Be easy to prepare and stable even when exposed to light, heat, or other environmental factors; [penetrating; not damaging to non-living materials]
(v) Be inexpensive and easy to obtain and use; [stable; easily prepared]
(vi) Not have an unpleasant odor. [no unpleasant to work with]"
(b) Note that different disinfectants typically have different strengths and weaknesses, and often what disinfectant one uses depends on circumstances
(c) Remember, the best thing one can do if unsure or ignorant of disinfectant abilities is to read the label.
2.5 SUMMARY OF TYPES OF DISINFECTION AND DISINFECTANTS
chemical reaction with pathogens
a small dose kills bacteria rapidly; residual can be maintained
in some cases, chlorination can cause the formation of trihalomethanes
Widespread use to disinfect water; also used in colour, taste, and odour removal, improving coagulation, and killing algae.
chemical reaction with pathogens
good disinfectant high cost; harmful to pregnant women
emergency treatment of water supplies; disinfecting small, non-permanent water supplies
chemical reaction with pathogens, handling difficulties; residuals hard to obtain; supply is limited
very limited use, primarily for treating swimming pool water
(sodium hydroxide and lime)
chemical reaction with pathogens
bitter taste in the water; handling difficulties
sterilize water pipes
chemical reaction with pathogens
good disinfectant; better virucide than chlorine; oxidizes iron, manganese, sulfide, and organics; removes color, odor, and taste, high cost; lack of residual; storage difficulties; maintenance requirements; safety problems; unpredictable disinfection; no track record
disinfection; treating iron and manganese, helping flocculation, removing algae, oxidizing organics, removing color, treating tastes and odors
UV light causes biological changes which kill the pathogens. Lack of dangerous by-products. lack of measurable residual; cost of operation; turbidity interferes with disinfection
small or local systems and industrial application.