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Agriculture workbook

2a Agricultural chemical safety - Pesticides

Contents

1. Facts

Many materials used in agriculture are classified as hazardous substances such as insecticides, herbicides and fungicides, collectively known as pesticides. Safety and health laws require that safety and health information must be provided in the form of Material Safety Data Sheets and labels so that the hazardous substances can be used safely.

A Material Safety Data Sheet is a document that provides information about a hazardous substance, how it should be used and how to avoid harm when using them. Manufacturers, importers or suppliers of any hazardous substance must provide sufficient information so the substance can be used safely.

The supplier of a hazardous substance must ensure that a current MSDS is provided when a person:

  • purchases the hazardous substance from the supplier for the first time
  • purchases the hazardous substance from the supplier at a later time and requests a MSDS, or
  • purchases the hazardous substance from a retailer who originally obtained it from a supplier and requests a MSDS.

The person in control of the of the workplace must:

  • set up and maintain a register that contains, as a minimum, a list of all the hazardous substances used and the MSDS for each substance; and
  • ensure the register is readily available to all people who might be exposed to a hazardous substance.

2. Control the risk

The hierarchy below ranks control measures from the most effective to the least preferable. However, not all types of strategies will be practical and more than one type of strategy may be needed for best exposure protection.

i Elimination and reduction

Use of a pesticide can be eliminated by removing the pest through manipulating the environment. At the same time there will be a benefit to production and the environment, including the elimination of wastes. Consider practices that involve:

  • better hygiene;
  • removing pest breeding areas;
  • biological control and beneficial insects;
  • rotating crops or alternative crop varieties;
  • physical barriers;
  • biotechnology and integrated pest management (IPM); and
    eradication.

Use these along with pest monitoring to reduce the frequency of chemical application. This is called integrated pest management, or IPM.

ii. Substitution

It may be possible to substitute a chemical with a less hazardous one. Examples of substitution include:

  • using a less toxic chemical;
  • using a less volatile chemical; and
  • altering the physical form such as replacing an emulsifiable concentrate formulation with a granular formulation or encapsulated product, which will reduce the handling risks.

iii. Isolation

Examples of isolation include:

  • using an air-conditioned truck or tractor cabins with properly functioning and maintained activated carbon filters designed to remove pesticide vapours. Check door seals for wear. Keep windows, doors and hatches or vents closed and air-conditioning on recycle during operations. Carbon filters must be maintained properly;
  • wearing a respirator if a carbon filter is not available. The use of air-conditioning on ’recycle‘ without carbon filters could contaminate the cabin over a period of time;
  • fencing off a contaminated dip site; and
  • closed chemical transfer systems which reduce the risk of contact with concentrate eg. induction hoppers, direct injection.

iv. Engineering control

Consider engineering controls for indoor work if air contamination is likely, for example in a green house or packing shed. Examples of engineering controls include:

  • using an extraction ventilation equipment (ventilator) to remove vapours after treatment;
  • using pumps to transfer (liquid) chemicals instead of pouring;
  • changing nozzles to control droplet size or spray pattern; and
  • using a purpose designed workplace with good natural or mechanical ventilation (adequate air movement).

v. Administrative controls and work practices

Administrative controls are implemented to ensure safe work practices are adopted in the workplace and that environmental impact is minimised. Examples of administrative controls include:

  • reducing the number of people exposed and excluding non-essential personnel from the area. For example, treating a building after normal working hours; minimising the number of workers during dipping;
  • limiting the time period of exposure for a worker;
  • prohibiting eating, drinking and smoking when handling chemicals;
  • providing and ensuring the use of adequate facilities for effective decontamination such as washing facilities;
  • ensuring that outdoor tasks are done at the most appropriate time of day to minimise heat stress or spray drift;
  • correctly calculating crop volume, area to be treated and amount of spray required;
  • correctly calibrating equipment;
  • restricting crop re-entry after spraying;
  • signs indicating hazards;
  • notifiying of neighbours; and
  • establishing procedures for disposal of waste and containers.

vi. Personal protective equipment (PPE)

PPE should only be relied upon where it is not possible to control exposure by one or more of the above measures. PPE should be used:

  • according to instructions on the label and the MSDS;
  • in an open field situation where engineering controls are not available;
  • when mixing, decanting or spraying; and
  • in some circumstances, as a back up for other control measures

Employers must provide PPE to workers where other control measures are not practicable. Ensure that:

  • all PPE is appropriate for the task;
  • all PPE is suitable for the wearer;
  • PPE is readily available, clean and in fully operational condition;
  • employees are trained in the use of the PPE, including the selection, fitting and maintenance and where appropriate when to discard disposable PPE;
  • employees wear the PPE as intended;
  • any maintenance, such as cleaning, is carried out; and
  • the likelihood of a secondary injury due to wearing PPE, such as skin rash or heat stress or dehydration caused by unsuitable clothing in hot conditions, has been assessed.

Protective equipment in use should have the appropriate Australian Standard number on the label. Various standards not only provide specifications but also indicate the type to be selected.

Use labels and MSDS as a guide. If in doubt as to suitability ask the supplier for a recommendation for the intended purpose. Also check the supplier’s specifications.

Clothing

Cotton or cotton/polyester blend full-length overalls, buttoned to the neck and wrists, should be worn during all operations. Although disposable overalls are light, comfortable and effective, they tend to easily tear under heavy use thus breaking the protection barrier. PVC pants and jackets are recommended where there is a risk of contact with spray, dust or spillage of pesticides. To minimise exposure when wearing overalls or PVC suits, care should be taken to make sure trouser legs are kept outside of boots and sleeves kept outside of gloves. This will reduce the likelihood of chemical leaking into boots or gloves.

Gloves

Nitrile or PVC, unlined flexible gauntlet gloves are considered excellent protection, as they are impervious to most solvents used in pesticide formulations. Leather or canvas gloves are unacceptable because their capacity to absorb the pesticide. Disposable gloves are only suitable for minor delicate tasks, such as cleaning spray nozzles and should only be used once and discarded. Never tuck sleeves into gloves.

Footwear

PVC calf length boots provide the best protection and are available as safety (steel cap) footwear. Never tuck trousers into socks or boots.

Headwear

Where necessary, a wide brimmed washable hat that protects the scalp should be worn. A hood fitted with respirator filters can also be worn.

Eye / face protection

When handling pesticides, especially concentrates, eye and face protection is essential. Safety glasses and goggles, although protecting the eyes, offer only minimal face protection. A full face shield and appropriate eye protection is recommended for total protection.

Apron

When mixing chemicals, it is essential to wear a PVC apron that covers the body from shoulder to below the tops of boots. Spillages can be quickly washed off without affecting the under clothing

Respirators

Particular attention needs to be paid to the selection of an appropriate respirator. The recommendations of the pesticide manufacturer, as stated in the MSDS must be strictly adhered to.

3. Recording control measures

Measures taken to control chemical exposure should be recorded.

Content of the record

The record should show the degree of the risk and how decisions were made concerning:

    • the selection, design, construction or adoption of any control measure used;
    • the selection and use of any PPE;
    • the arrangements for training to ensure an appropriate application procedure is followed and the equipment is correctly used (unless the operator is licensed or appropriately certificated); and
    • suitable weather conditions and restrictions on the chemical use if the weather is unfavourable.

For most users a simple record attached to the original MSDS or written on the MSDS and dated would be sufficient. This must be kept for at least five years.

4. Spraying pesticides

Spray drift controls

One of the major problems encountered during the use of pesticides is the potential for spray drift to expose other workers, neighbours, members of the public.

Identify sensitive areas where spray drift is likely to have the greatest impact, such as water sources, occupied buildings, public roads, schools and other public amenities, livestock, crops and pasture.

Separate the application site and the area of potential risk with a barrier, such as vegetation, or distance. For example, encourage vegetation growth to act as a barrier. Wherever possible, a buffer zone should be left between a sprayed and unsprayed area.

Prepare property plans as a means of communicating to others all the factors which need to be considered when applying chemicals on a property. The plan should identify houses and buildings, neighbouring properties, sensitive areas, roads and access points, public roads and public places, watercourses and storages, paddock boundaries, and powerlines and aerial hazards such as transmitter towers. The property plan is both a tool for communicating with neighbours and a management tool when spraying contractors are used or workers are given directions.

Communicate with neighbours to minimise drift problems and avoid conflict. Communication could include: pre-season discussion to identify activities involving chemical application, chemicals used and potential interactions with neighbours, when to notify neighbours prior to application and agreement on conditions under which application will not proceed or be abandoned.

Check wind speed and direction. Spraying should only take place when the breeze is blowing away from an area that may be at risk from drift.

Choose equipment that is designed to reduce or eliminate drift (if permitted by the label instructions). Equipment should be used according to the manufacturer’s instructions and be the most appropriate for the task in hand, for the particular pesticide and target requirements.

For each type of application equipment, variables such as nozzle type, hydraulic pressure, height of delivery and the presence or absence of a directed airstream will affect the size and movement of droplets produced, and the efficiency with which they impact on the target. Application equipment needs to be set up to maximise pest control efficiency and to minimise spray drift.

Weather conditions for spraying

To minimise spray drift it is necessary to monitor weather conditions during and immediately after application.

Temperature affects the rate of evaporation, particularly water based sprays. Evaporation can reduce the size of droplets making them more drift prone. Formulations, which rely on light oil as a carrier, are less prone to evaporation.

High relative humidity is preferable to minimise drift that can occur through evaporation. Applications at temperatures above 30 degrees Celsius and at relative humidity’s below 45 per cent increase the risk of drift.

Ensure that spraying is done in cross-wind conditions rather than directly into or with the breeze. Application should be avoided in calm, stable conditions which may occur early in the morning, late in the afternoon or during a temperature inversion.

Rain may cause run-off of the pesticide with a risk of environmental contamination. This should be taken into account when assessing the risk to the environment. Check the rain-fast period. Pesticides must not be applied if rain is likely to wash the pesticides from the site of application.

Inversion: Do not spray under conditions of atmospheric temperature inversion, where air closer to the ground cools faster than the air above it, and forms a layer where air temperature increases with altitude instead of decreasing. Small spray droplets released into an inversion layer can remain suspended and drift long distances. Inversion conditions are most likely in the early morning and late afternoon in the absence of wind, and are often marked by fog, smog or smoke drifting at a constant height instead of rising.

Aerial application: Aerial application and droplet capture by the target crop, are improved where cross winds create turbulence in the crop. Cross winds of between three to ten kilometres per hour are preferable for aerial application to broad acre crops. In the case of bare earth or fallow, lower cross wind speeds are preferable. No application should occur at speeds above 15 kilometres per hour unless specific drift minimisation strategies are in place. Variable low speed winds should also be avoided.

If conditions are not suitable to minimise potential risks from drift, the spray operation should be delayed until conditions are suitable.

Re-entry periods

The re-entry period is the period in which a treated field must not be re-entered by unprotected people after the application of a chemical on a crop. Look to see if the re-entry period is on the label. Workers and others must be advised of the correct time lapse. It is important to observe the re-entry period to avoid skin contact with sprayed foliage.

Where no re-entry period is stated, a minimum of 24 hours should be observed or until the chemical has dried upon the crop, whichever is the later, or unless appropriate PPE is worn. Caution should be exercised entering wet crops where chemicals have previously been applied, irrespective of the time lapse between application and re-entry.

Even after the re-entry period has been observed, some PPE may still be necessary.

5. Further information

Related information