Herbicide safety

Page last updated: Monday, 2 February 2015 - 5:08pm

Please note: This content may be out of date and is currently under review.

Herbicides can be used safely, provided appropriate precautions are taken as required by the chemical label or as described in safety data sheets (SDS).

First aid

If you feel dizzy, nauseous, have severe headaches, disturbed vision or stomach upsets within a few days after handling herbicides: seek medical advice, ­tell the doctor all you know about the chemical used.

For immediate first aid treatment ‘read the label on the container’.

When using pesticides consistently: have regular medical checks.

Poisons Information Centre
24 hour hotline telephone: 13 11 26

Toxicity of herbicides

Pesticides usually have several toxicity ratings. They are oral, dermal, acute and chronic.

Oral toxicity

The oral toxicity of a herbicide is determined by laboratory testing at various doses. From these trials the LD50 value is calculated. This is the amount of chemical tested in animals, expressed as mg of active ingredient per kilogram of body weight, required to kill 50% of the test group (usually rats or mice). The lower the LD50 number, the more toxic is the chemical.

Oral LD50 of some well known compounds

Caffeine

DDT

Aspirin

Penicillin

Salt

Petroleum oils

150mg/kg

420mg/kg

750mg/kg

1000mg/kg

3000mg/kg

1000–

10 000mg/kg

LD50 of some well known herbicides*

Trade name

Active ingredient

Oral LD50mg/kg

Dermal LD50mg/kg

2,4-D

2,4-D

639–764

>1600–2400

2,4-DB

2,4-DB

700

n/a

Ally®/Brush-off®

metsulfuron methyl

>5000

>2000

Amitrole

amitrole

1100–24 600

>2500–10 000

Atrazine

atrazine

1869–3090

>3100

Basta®

glufosinate

2000

>4000

Broadstrike™

flumetsulam

>5000

>2000

Bromicide®

bromoxynil

190-270

>2000

Casoron®

diclobenil

2700-6000

>2000

Diuron

diuron

3400-3700

>2000

DSMA

DSMA

1800-2800

>10 000

Eclipse®

metosulam

>5000

>2000

Garlon™

triclopyr

713

>2000

Glean®, Lusta™ etc

chlorsulfuron

5545

>2500

Gramoxone®

paraquat

112-150

911

Hoegrass®

diclofop-methyl

481–693

>5000

Hyvar® X, Bromacil

bromacil

2000

>5000

Kamba, Banvel™

dicamba

1707

>2000

Linuron

linuron

1000-4000

>2000

Logran®

triasulfuron

>5000

>2000

Londax®

bensulfuron

>5000

>2000

Lontrel™

clopyralid

>4300

>2000

MCPA

MCPA

800

>4000

MCPB

MCPB

4700

>2000

Propon

2,2-DPA

3860-9330

>2000

Ramrod®

propachlor

1200

>20 000

Reglone®

diquat

230–440

>793

Roundup®

glyphosate

5600

>5000

Simazine

simazine

500–10 000

>2000

Spinnaker®

imazethapyr

>5000

>2000

Spray.Seed®

paraquat + diquat

150

911

Starane™

fluroxypyr

2450

>5000

Terbutryn

terbutryn

500–2500

>2000–20 000

Tigrex®

diflufenican

>2000

>2 000

Tordon™ 75D

2,4-D + picloram

n/a

n/a

Tordon™ Double Strength

triclopyr + picloram

n/a

n/a

Tordon™ granules

picloram

8200

>2000

Tribunil®

methabenzthiazuron

>5000

>5000

Trifluralin

trifluralin

>5000

>5000

Velpar®

hexazinone

1 690

>5278

* The above acute LD50s for herbicides commonly used in Western Australia were extracted from 'The Pesticide Manual: a world compendium' (12th edition) 2000, the British Crop Protection Council.

Although the toxicity of some herbicides varies with the route of entry into the body (oral, inhalation, dermal), in general, the acute oral LD50 figures gives a good indication of the relative toxicity of the herbicide. The poison schedule is dependent on other factors as well as LD50 of the product. For example, all arsenics are carcinogenic and hence are placed in the S7 category.

Acute toxicity

Acute toxicity is the toxicity of a single dose, such as could happen in a chemical spill onto the skin or by accidental spilling.

Chronic toxicity

Chronic toxicity is the long-term toxicity of a chemical after repeated low-level exposure for an extended period.

The solvent or emulsifier used in the formulation of the herbicide often increases the toxicity and makes the compound far more harmful than the pure chemical.

The properties of herbicides are documented in safety data sheets (SDS) which describe the chemical and physical properties of a material and provides advice on safe handling and use of the material. In Australia chemical manufacturers and importers must produce an SDS for any chemical that is a hazardous substance and make it freely available to workers handling the substance.

These information sheets are available from the herbicide manufacturer or major resellers. These can also be found online at the APVMA website or by searching the product name and the respective SDS in the chemical manufacturer's website.

An SDS includes:

  • section 1: identification of the material and supplier (contacts)
  • section 2: hazards identification (including risk and safety phases)
  • section 3: composition / information on ingredients
  • section 4: first aid measures (necessary first aid information)
  • section 5: fire-fighting measures
  • section 6: accidental release measures (personal and environmental precautions and disposal procedures)
  • section 7: handling and storage.

Storage of herbicides

Take care that herbicides are stored safely when not in use. Most cases of pesticide poisoning occur in children who have been allowed to play with herbicide containers. Accidents are avoidable if commonsense precautions are taken.

Safe storage of herbicides

  • Store all herbicides in a locked storage cupboard or shed set aside for that purpose.
  • Do not store near foodstuffs, seeds or fertilisers or other pesticides.
  • Keep herbicides only in their original labelled container. Never store in drink bottles or unmarked containers.
  • Seal containers adequately and store them in relatively cool conditions for maximum storage life.

Handling herbicides

Hazard

The use of a chemical becomes hazardous (irrespective of its toxicity) if it is formulated or used in such a way that human exposure is increased and poisoning occurs.

The relative hazard of pesticides can be readily judged from the signal words that appear at the top of the principal panel of the label of the pesticide container. These words must appear on pesticide labels.

Exposure

There are three main ways chemicals can enter our bodies:

Skin absorption (dermal)

Skin absorption is responsible for the majority of occupational poisonings. Spraying without protective clothing and general carelessness when mixing and spraying are responsible for most poisoning cases in this group.

Inhalation (breathing)

No protective equipment, mixing chemicals in a badly ventilated space, and working downwind when spraying is responsible for inhalation of chemicals.

By mouth (oral)

Chemicals may be swallowed when eating with contaminated hands, smoking and blowing or sucking to clear blocked nozzles on the spray unit.

Children sometimes poison themselves by drinking chemicals left within their reach. All chemicals should be properly stored.

Protective clothing

Gloves

Unlined, flexible gauntlet-type gloves are considered best.

  • PVC (not rubber or surgical plastic gloves), Viton and Nitrile Rubber (NBR) are impervious to most solvents and are most suitable.
  • Disposable/surgical gloves are suitable only for delicate jobs such as cleaning nozzles, provided they are used once only, and then disposed of properly.
  • Replace used gloves regularly.
  • Never wear leather gloves, or gloves that leak.

Overalls

  • Full length overalls should be worn during all spraying operations. Light cotton/polyester type is available for summer. These must be washed every day. Bib and brace type are not suitable.
  • Full length breathable nylon fabric overalls are excellent.
  • PVC pants and jackets are very good when spraying in winter. They are essential for the more hazardous horticultural spraying operations.
  • There are several disposable overalls on the market. Polyethylene and polypropylene fabric will prevent droplets from spray drift contacting skin, but are not waterproof.

Boots

  • While rubber boots are satisfactory, PVC boots are better. Steel caps in the toe offer extra safety but are not essential when spraying.
  • Never wear leather boots while spraying and throw out leaking boots.

Eye and face protection

  • Always wear eye protection when handling, especially when pouring chemicals and solutions.
  • A face shield protects the whole of the face but is difficult to wear with the conventional twin cartridge respirator.
  • Goggles and safety glasses protect only the eyes. However, they can be worn with a respirator.

Aprons

Most operators wear only cotton overalls while spraying. PVC aprons are quick to put on before chemical drums are lifted for pouring. Any spillage can be quickly washed off without affecting the overalls. Aprons should cover from the shoulder to below the top of the boots.

Respirators

  • The half-face twin cartridge respirator usually meets most spraying requirements. They come in three sizes to suit various faces.
  • The half-face single cartridge is satisfactory but the cartridge should be changed more often than the twin cartridge mask.

Respirator cartridges

The multipurpose agricultural filter is best for general spraying. It contains both a cotton filter and activated carbon to remove both dust and organic solvent vapour.

Cotton and paper masks are satisfactory for removing dusts but are not suitable where organic solvents are used. Only activated carbon will remove these vapours.

The dust filters are full when it becomes hard to breathe. Activated carbon filters are full when the operator can ‘smell’ the chemical being used. They can be tested by trying to smell perfume through the mask. If you can smell the perfume replace the filters. (This is assuming the mask has a snug fit on the operator’s face.)

Operators with heavy beards are likely to find difficulty obtaining a proper face fitting respirator.

Activated carbon filters must be stored in a convenient sealed container such as a plastic lunch box to maximise their useful life. If left out they will continue to absorb organic vapours like diesel and petrol.

For added protection

  • Always carry at least 20L of water, soap and paper towelling with the spray outfit for washing hands, face and other areas of exposed skin, and especially your eyes.
  • Wash thoroughly with soap and water after mixing chemicals and before eating, drinking or smoking or after work.
  • Barrier cream may be used on the hands but is not a protection against chemical penetration.

Disposal of containers and herbicides

Empty containers

  • Rinse empty containers three times with water and tip rinsate into spray tank. This is best done as the containers are emptied during spraying operations.
  • Never use chemical containers for water storage or livestock feed troughs. Contact local shire for details where used containers can be deposited and local herbicide suppliers to obtain information on reusable/refillable containers.

Non-returnable containers

  • Never burn any herbicide container. They may give off poisonous smoke or damage nearby plants or crops.
  • Chop holes in top, bottom and sides of metal containers, crush under tractor wheel or flatten with a sledge hammer so that they cannot be reused nor collect water. Do not use oxy-acetylene torches to cut holes.
  • Crush metal, plastic, cardboard or fibre drums and break glass containers, then bury them at least 0.5m deep at a safe site, such as a LGA landfill site. Do not bury them in watercourses or where they might contaminate water supplies.

Unwanted pesticides

  • Only mix enough pesticide to do the job.
  • First offer unwanted pesticides for use by a responsible person. If this is not possible, select a well-drained site away from desirable vegetation, and where lateral movement of groundwater will not occur. Dig a pit at least 0.5m deep, spread a bag of lime in the bottom and pour the diluted pesticide over the lime. Then cover with soil. Permanently mark the site and show it on the farm map.
  • Never incinerate unwanted pesticides.

Further information

Further information on controlling declared plants can be found through the Declared plant control handbook link.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080
Andrew Reeves
+61 (0)8 9780 6224