In a well planned spraying operation the amount of pesticide solution required for the job should have been worked out carefully so that there is little or no pesticide left over.

Pesticides are poisonous and it is bad for the environment and a danger to people and other animals to leave them lying around. Most of the pesticides used in environmental health work will not last very long after they have been mixed with water. This means that preparing too much spray is a waste of money and effort because the pesticide will not be effective if it is used later.

Unused pesticide

If there is any pesticide left over at the end of a spraying operation then it is important that it be disposed of correctly. This means getting rid of the chemical so that it has no harmful effect on the environment, including people and their pets.

Note: Rather than have pesticide left over, go back over the job and use up the small amount that may be leftover, particularly if the pesticide is being used on weeds or the outside of a building for insects.

If it is not possible to use up all the mixed pesticide, then the following steps should be taken to get rid of leftover pesticide safely:
  1. If further spraying is going to take place the next day then use any left over pesticide on that job. However if no more spraying is planned then follow the procedure as below.
  2. Choose a place well away from community buildings and meeting/play areas, any streams, water supply areas, or low-lying areas where water may collect or there may be a high water table. Near the storage shed or at the rubbish tip may be appropriate.
  3. Dig a hole 50 cm deep.
  4. Cover the bottom of the pit with a 25 to 40 mm layer of hydrated lime. Pour the unwanted pesticide into the hole.
  5. Cover with soil.
Fig.  5.38: Unused pesticides must always be disposed of safely.
Fig. 5.38: Unused pesticides must always be disposed of safely.

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Empty pesticide containers

Empty pesticide containers must also be disposed of so that they cannot cause any possible danger to the environment, including people.

The best place to dispose of empty pesticide containers is at the community's rubbish tip.
  1. These are the correct ways to dispose of empty pesticide containers:
    All glass, metal or plastic containers should be rinsed out with water at least 3 times.
    The wash-water should, of course, be disposed of correctly so that it does not become a danger. However, if the container is emptied as the spray solution is mixed, the wash-water can be added to the spray solution. The wash-water should have little effect on the strength of the solution. Paper packets cannot be rinsed out.
  2. The lids of all containers should be removed before disposal.
  3. Glass or plastic containers must be buried deep in an isolated area away from water supplies.
    If it is safe to do so, it is a good idea to break glass containers before disposal. Plastic containers must be punched with holes so that they cannot be used to carry water.
  4. Glass or plastic pesticide containers which cannot be broken or punched with holes must never be left around in case people use them for some other purpose.
  5. Each metal container should be made unusable by punching holes in the top and bottom and then crushing it. Flattened containers are easier to bury or dispose of at the tip.
    Never burn pesticide containers because they may give off poisonous gases. Never use these containers or any pesticide treated materials, such as wood, on fires.
Fig.  5.39: Empty pesticide containers must be disposed of safely
Fig. 5.39: Empty pesticide containers must be disposed of safely.

If the EHP has any worries about the disposal of leftover pesticides or empty pesticide containers then he/she should contact the EHP supervisor or an EHO.