Causes of Infestation
Cargoes can become infested and damaged by the following common forms of pest or vermin.
Rats consume approximately their own weight in food per week. The damage that rats can do to a cargo of foodstuffs is compounded by the fact that the presence of rats will almost certainly mean that the cargo has to be condemned. This is due to the fact that rats are carriers of virulent diseases.
Control of rats aboard ship is done by fumigation and a periodic renewal of a "De Rat" Certificate. In the case of containerised cargo, care should be taken to inspect the cargo during packing for signs of rats having penetrated the cargo.
Beetles, moths and mites are known to cause damage to a wide range of commodities. Each insect grows from an egg produced by an adult female. The egg of the beetle and moth hatches into a caterpillar which actively feeds on cargo. This is the greatest cause of damage from infestation.
Caterpillars moult several times during their life cycle before entering a pupal stage which releases the moth to restart the cycle. Mites are hatched from eggs producing an insect which goes through a series of development stages before reaching adulthood.
- Lice are often found in bales of rags. A reliable sanitary certificate normally accompanies the cargo.
- White Ants are found in certain tropical woods and often in flat dunnage.
- Cockroaches are found in various cargoes including hollow bamboo and old cord wood.
- Sirex Wood-Wasp is found in timber dunnage and is particularly outlawed in Australia.
- Maggots are found in animal hoofs, horns, bones and skins.
- Tropical Warehouse Moth is found in cocoa beans and coffee.
- Weevils are common in bran rice.
- Copra Beetle is found in coconuts and cereals.
- Black Mould Parasite is found with onions.
- Sitophilus Zeamais is common in maize.
- Tribolium Castaneum is found in wheat flour
Infestation is obvious when insects are visible on bags or bulk, but it may be that insects are feeding inside the foodstuff itself. This can happen for example with wheat grains and coffee beans. Tropical countries are associated with the origins of particular insects, however cross contamination with other infested cargoes is a common cause.
There are four types of damage resulting from insect or mite infestation:-
- Boring and nibbling mixed with webbing and excreta.
- Loss in weight and heating. It is important to note that heating can be caused in dry materials solely by the activity of insects.
- Water damage. Essentially a surface phenomenon confined to the top few inches of the cargo resulting from "hot spots" and insect activity.
- Depreciation of value. A good example of this is Tribolium beetles within desiccated coconuts which cannot be removed by a commercially practicable process.
Fumigation is the recognised means of combating infestation by the application of fumes to disinfect or purify. There are several substances used for this purpose which are listed below. Further sections are provided on the disciplined procedure necessary for applying fumigants as well as the relationship to the IMDG code for hazardous cargo.
Types of Fumigants
1. Methyl Bromide (Bromomethane):
Methyl Bromide, at normal temperature, is a colourless gas 3.27 times heavier than air. The pure gas has a faintly sweet smell but it normally has a marker added for warning which causes watering of the eyes.
There is widespread international concern over Methyl Bromide because of its properties as a category one ozone depletant under the Montreal Protocol of 1992. Not withstanding its abilities as a fumigant there is a mounting consensus that a more suitable substance must be found by the end of the century. Methyl Bromide is highly toxic to mammals and is the most widely used fumigant for timber, agricultural products, empty containers, foodstuffs, seeds and plants. In particular Australian quarantine clearance by AQIS requires this method which includes fumigation against :
- Weeds and organisms within soil and compost,
- Insects and mites,
- Infestation in fresh fruit,
- Within nursery stocks of plants.
Effect on foodstuffs: After fumigation the bulk of methyl bromide is removed by aeration although there may be small residues. There can on occasion be a chemical reaction with certain food products if some absorption takes place.
Methyl Bromide is absorbed by oils, fats and finely ground materials. It can also react with materials containing sulphur to cause discoloration or odour. The following materials are among those which should NOT normally be fumigated by Methyl Bromide.
- Butter, lard, fats, avocado, soybean flour, flours and baking powders,
- Bone meal, charcoal and cinder blocks,
- Furs, felts, horsehair, pillows, rugs and papers,
- Iodised salt,
- Leather goods and photographic chemicals (excluding film).
- Photographic prints,
- Rubber goods,
- Woollen goods
Health Warning : Exposure to Methyl Bromide has in the past resulted in a number of deaths. A particular danger is that signs of poisoning may be delayed for several hours following exposure to the gas. There is no significant antidote and the human body can absorb it by inhalation and via the skin.
Headache, dizziness, eye irritation, coughing, nausea, abdominal pains and numbness of the feet are early indications of poisoning.
Methyl Bromide is usually administered from approved cylinders or cans. It is important to stress the use of the correct protective clothing during fumigation.
Guideline quantities : For ANZ destinations - 5.0 lbs per 1000 cft or 80 gms/cbm For USA destinations - 4.5 lbs per 1000 cft or 72 gms/cbm For other destinations- 3.0 lbs per 1000 cft or 48 gms/cbm
Phosphine used for fumigation purposes is usually produced by the reaction of atmospheric moisture with slow release formulations containing aluminium or magnesium phosphide.
Phosphine is highly toxic although it requires a relatively high temperature and long exposure period to be effective. Under normal conditions Phosphine is a gas and is colourless and odourless. A fishy or garlic-like smell may be evident due to impurities.
A significant fire/explosion risk associated with phosphine is reduced by using metal phosphides specially prepared for fumigation purposes. Care must be taken during use to isolate any electrical connection (switches can be covered in paraffin wax) and any sources of ignition must be removed.
Phosphine is used for fumigating a wide band of insects and pests. It has a low degree of absorption by foodstuffs and penetrates well into the stored product.
Australian AQIS recognise its advantages over Methyl Bromide on milled and oily commodities such as flour, soybean flour, fishmeal, nuts and oilseeds. It is however not favoured for use on timber due to concerns over its ability to penetrate the material.
Health Warning : Very poisonous and very similar symptoms to those of Methyl Bromide if exposed to it. A notable effect is chest tightness and difficulty in breathing.
Phosphine preparations for fumigation are dispensed as :
- Powder sachets
- Degesch plates impregnated with metal phosphide formulations and sealed prior to use
- Bag blankets or beltsMixed in cylinders with CO2 with 3% phosphine.
- Tablets or pellets,
Guidelines on tablets : 3 tablets per CBM. The advised temperature for Phosphine NOT to be used below 10 deg C.
3. Sulphuryl Fluoride:
Sulphuryl Fluoride (Vikane) is used extensively in the USA to control insect pests in timber. It should not be used on living plants and foodstuffs. It does have an advantage over Methyl Bromide in that it does not have any harmful effects on photographic supplies, metals, electronic components, paper, leather, rubbers, plastics and wallpapers.
4. Ethylene Oxide:
Approval for use in foodstuffs was withdrawn by Australian authorities (AQIS) in 1988 due to concern over toxicity of residues formed in some foods. The properties of Ethylene Oxide as an insecticide and effectiveness in devitalising seeds make it specific to special needs such as fumigating rice straw matting.
A major drawback is the explosive qualities of Ethylene Oxide requiring it to be normally applied under vacuum.ç
5. Ethylene Dibromide (EDB):
Used for years as a treatment for fruit fly in fresh fruit and vegetables and agricultural needs this form of fumigation has gradually been replaced.
Reference to the IMDG Code
Reference is made to the IMO/ILO guidelines for packing cargo in freight containers or vehicles and recommendations on the safe use of pesticides in ships.
Only a cargo transport unit that can be closed in such a way that the escape of gas is reduced to a minimum, should be used for the carriage of fumigated cargo.
A closed cargo transport unit under fumigation should not be allowed on board until sufficient time has elapsed to allow the attainment of a reasonably uniform gas concentration throughout the cargo. Because of variations due to types and amounts of fumigants and commodities and temperature levels, the period which should elapse between fumigant application and loading should be determined by the competent authority. Twenty four hours is normally adequate for this purpose.
The master should be informed prior to loading of a cargo transport unit under fumigation. These should be identified with a warning sign affixed to the access doors incorporating the identity of the fumigant and the date and time of fumigation. The transport documents for a closed cargo transport unit should show the date of fumigation and the type and amount of fumigant used.
Equipment for detecting the fumigant gas or gases should be carried on the ship, with the instructions for its use. Fumigants should not be applied to the contents of a cargo transport unit once it has been loaded aboard a ship.
The provisions of this code should NOT apply to a closed cargo transport unit which has been ventilated after fumigation to ensure that no harmful concentrations of gas remain. Such a unit should also have the warning signs removed.
Health & Safety
Due to the very serious hazards, both health and fire, associated with fumigation, only competent specialist people should be employed to undertake this operation. When opening a container which has undergone fumigation, care must be taken to guard against residual levels of the fumigant. This will depend on the time since fumigation and the amounts applied. The container must be properly ventilated and suitable equipment used (Draeger Sets) to measure for residual gas prior to unstuffing.
How to Apply Fumigants
As a general rule there must be a minimum of two person conducting any fumigation.
Secure fumigation sit: Fumigation should be conducted at an approved and isolated area specially designated for this purpose. Notification of planned fumigation should always be provided to relevant parties so that the danger to staff is flagged in advance.
Protective Equipment: Special protective suits are required which have respiratory protective equipment (RPE). This equipment must be maintained properly and tested at regular intervals.
Inspect container prior to stuffing to ensure that there are no holes in the container's side panels, roof, floor or doors.
Seal any ventilation ducts on the OUTSIDE of the container using grip tape or suitable equivalent.
Many CCNI GP containers have small semi vents fitted in way of the top corner castings on each side panel. They should be sealed on the outside of the container.
Alternative methods of sealing cargo for fumigation include sealing the container or cargo under gas-proof sheets (Not commonly used).
Ventilated containers must be sealed along their top and lower side vents on the outside.
Fantainers can be sealed on the underside intake vent either with tape or by placing the container on a cushion blanket.
On completion of stuffing and observing the relevant safety procedures referred to previously, the fumigant is applied inside the container, with a door cracked open, and doors then quickly closed.
The amount and type of fumigant will be determined by the temperature, commodity, cargo cubic and country of destination. (See guidelines under Methyl Bromide and Phosphine).
A competent contractor will have a chart to readily determine the amount required. If it is the intention to ship the cargo under fumigation then the cargo must be treated as IMO Haz Class 9 and booked through the existing company procedures for hazardous cargo. The relevant packing declaration must accompany the cargo and the container appropriately labelled.
At least 24 hours must elapse after fumigation prior to the container being shipped. The reason for this is to allow the fumigant to properly permeate the cargo. In cases where the cargo requires ventilation during the voyage e.g. Coffee, the vents must be unsealed prior to shipment. In this case the container should be rendered non hazardous by opening the doors to fully vent the container prior to shipment.
A gas free certificate should be issued by the company conducting fumigation operations which then exempts the cargo from hazardous regulations. If shipping gas free then time scales must be carefully considered up to the arrival of the ship designated to lift the cargo. Sufficient time must be given to allowing the fumigant to act as well as making the container gas free afterwards. Fumigation can also be carried out on arrival at the destination port and will be subject to the port health requirements of that country.