As the weather warms and days lengthen, your attention may be turning to that forgotten patch of your backyard. This week we’ve asked our experts to share the science behind gardening. So grab a trowel and your green thumbs, and dig in.
Gardening is good for your health, but it can pose some risks if you’re not careful. For example, you should use sensible protection against the sun to prevent cancer, a significant cause of death in Australia.
Further reading: The science is in: gardening is good for you
Gardening in Australia also requires, to varying degrees depending where in the country you are, pesticides, herbicides and fertilisers. There is an enormous number of agents with multiple formulations, depending on what you are doing, what plants you are tending, the size of your garden and the kind of soil.
These garden treatments are designed to be specific and potent, so they can be applied less often and work (mostly) only on the things you want them to work on. All of them – even the “natural” ones such as sulfur dusts to control caterpillars and mildew – are chemicals, which means they have health risks.Yates Tomato and Vegetable Dust product webpage/Screenshot
Regulation of chemicals
While not perfect, gardening product safety is regulated in Australia. Let me introduce you to the Australian Veterinary Medicines and Pesticides Authority. This body regulates pesticide (a substance that kills pests such as insects and weeds) and herbicide (a substance that kills only weeds) products sold in Australia.
The AVPMA regularly reviews products for safety concerns, though the reviews may be decades apart. It co-ordinates with World Health Organisation bodies and its counterparts in Europe, Canada and the United States.
Given the sheer number of compounds and formulations available, I can’t possibly cover the safety of all chemicals, or even all groups of chemicals. If you are concerned about a particular product, you can search the AVPMA site for the ingredients in a given pesticide, herbicide or fertiliser.
This may be tricky, as some will not necessarily have a chemical name on them, just the trade name. However, most pesticides and herbicides from reputable companies should have a material safety data sheet (MSDS) with them. This should give you the details you need to check through the AVPMA site.from shutterstock.com
There are three ways to deal with pests (well, four if you count laboriously picking them off your plants): repel, smother or poison them. All these can harm people if they are exposed to significant quantities. But in an urban garden, exposure to pesticides is typically small and of limited duration.
Common smothering pesticides are oils such as petroleum oils used to control, say, leaf pests on citrus, or pests in a variety of other circumstances. If you apply these often, without gloves, you might get skin irritation; or lung irritation if you breath the spray in. So always follow the directions, which include wearing gloves and spraying so the wind doesn’t blow the spray back into your face.from shutterstock.com
Modern poisoning insecticides include the pyrethrums which are found naturally in some chrysanthemum flowers. Both the natural pyrethrum and synthetic pyrethroids have low toxicity to humans – particularly at the doses found in garden products. Continuous use of pyrethroid insecticides has no health implications for humans if instructions are followed.
Neonicotinoids are synthetic insecticides that mimic nicotine, which is toxic to insects. These have a place in pest control if used thoughtfully and sparingly. Unlike pyrethroids, these insecticides target a pathway in the insect nervous system shared with humans, so could potentially harm us.
When used as directed, poisoning should not occur and animal studies suggest human exposure should not lead to significant health effects. Neonicotinoids are toxic to bees, although Australia has not had the big bee crash seen in the US and parts of Europe.
Chronic use of neonicotinoids in a human gardening population has not been assessed for long-term health effects, but a small study of agricultural workers has shown no effect of chronic exposure. Another small study, however, suggests some association with memory loss.
Again, there is a bewildering variety of herbicides, depending on what weedy species is being targeted and how the weed is being killed.
Right out of the gate is glyphosate, used for broadleaf weeds. This chemical, commonly sold as Roundup, caused some controversy after the International Agency for Research on Cancer (IARC) concluded it was a probable human carcinogen.
Authors: Ian Musgrave, Senior lecturer in Pharmacology, University of Adelaide