The audit sheet · Check 05
Pesticide hazards at work: the four classes and what raises the risk
Victoria’s Department of Health groups the pesticides most commonly used in pest control into four chemical classes: organophosphates, carbamates, pyrethrins and synthetic pyrethroids, and some are more hazardous than others. Organophosphates are generally extremely toxic, particularly when concentrated, while synthetic pyrethroids are less toxic to mammals than the other three but quite toxic to fish.
General information, not safety or medical advice. In Victoria, WorkSafe Victoria administers the workplace safety law on hazardous substances.
Why every pesticide is a hazard
Pesticides work because an ingredient interferes with natural body functions, and some of those functions are the same in people and other animals. The department says there is a risk with any pesticide, whatever its class.
The department’s 2010 guidelines for operators went further: because pesticides are designed to kill or cause harm, they should all be treated as hazardous, even when they are not officially classified that way. The class is not always written on the label or the safety data sheet, the department notes, which is one reason to ask.
The four classes, side by side
| Class | How it acts | Hazard to people, as described | Also noted |
|---|---|---|---|
| Organophosphates | Block an enzyme the nervous system needs, so nerves are overstimulated. People rely on the same enzyme. | Generally extremely toxic, particularly concentrated. Can be absorbed through the skin, the stomach or the airways. | Generally more persistent than the other classes; use has fallen in favour of less toxic, shorter-lived products. |
| Carbamates | Act on the same enzyme; in people the effect is reversible. | Moderately toxic. Symptoms usually start within minutes and last a few hours; recovery is typically faster than with organophosphates. | Usually break down within days to weeks. |
| Pyrethrins | Natural extracts from certain chrysanthemum flowers that overstimulate nerves on contact. | Much more toxic to pests than to mammals, which break them down. | Not very persistent, being unstable in light and air. |
| Synthetic pyrethroids | Made versions of pyrethrins, acting the same way. | Less toxic to mammals than the other three, though poisoning can still occur at high exposure. | Quite toxic to fish and other aquatic life; more persistent than pyrethrins. |
The department also notes that the licence authorisations on an operator’s card describe the kind of work they are qualified for, not the chemical class they use. The licensing guide covers the authorisations.
Three things that raise the hazard
Concentration
Pesticides are generally most toxic in concentrated form, so the department advises particular care when undiluted chemicals are handled and mixed, with protective equipment worn as the label and safety data sheet set out.
Persistence, especially indoors
A pesticide’s half-life is the time it takes for the applied concentration to halve; the longer the half-life, the more persistent it is. Indoors, the sunlight, rainfall and soil microbes that speed up breakdown outdoors are missing, so a pesticide may last longer inside. For a kitchen, that is the case for asking how long a product lasts and where it will go.
Drift onto food
Synthetic pyrethroids do not dissolve easily in water but stick strongly to surfaces, and the department warns of spray drift reaching foodstuffs, such as vegetable gardens, and then being eaten. In a business with a kitchen garden or an outdoor servery, that is worth naming when the treatment area is agreed.
Who is nearby
Where possible, the department says, the lowest-toxicity pesticide should be used, particularly around pregnant women, infants, children and older people. A business that serves or employs any of them can raise that before the job.
What the operator should tell you
The department lists the information pest control operators should give their clients. In brief:
- The full name of the pesticide and its toxicity rating.
- Its potential health risks, how it will be applied, and to which areas.
- The re-entry period, if it is used indoors.
- What you can do before and after to reduce exposure: covering or removing food and cooking utensils from the treated area, staying away while it is mixed and applied and until it is dry (generally four to six hours), ventilating on return if there is a chemical smell, and cleaning benchtops and kitchen utensils before preparing food if it was used indoors.
The workplace law in Victoria
Victoria is the only Australian jurisdiction that has not implemented the national model work health and safety laws, Safe Work Australia notes, so its own Occupational Health and Safety Act 2004 applies. That Act and its 2017 regulations, administered by WorkSafe Victoria, require employers to protect employees who use hazardous substances. Every Victorian pest control licence holder must comply with the same Act, and must hold current safety data sheets for the chemicals they use.
If someone is exposed
Healthdirect says symptoms of pesticide poisoning appear within two days of exposure and range from mild to severe, and can be life threatening in severe cases. Low-level exposure over a long period can also cause poisoning. When it does, symptoms may take longer to appear. Even with no symptoms yet, healthdirect advises ringing the Poisons Information Centre (13 11 26) if pesticide poisoning is suspected. Knowing the full chemical name of the product helps with first aid, which is why the Better Health Channel suggests asking for it before a treatment.
Call the Victorian Poisons Centre, whose number is on the Better Health Channel’s Poisons Centre page; its staff give first aid information by phone and say whether an ambulance is needed. In an emergency, call triple zero (000), not the Poisons Centre: that includes anyone who has collapsed, has stopped breathing, is having a seizure or has gone into anaphylactic shock.