Working around the legacy of lead: how safe is your veggie patch?

Lifestyle

A third of veggie patches in Australia’s inner cities have levels of lead that exceed safe guidelines, according to Sydney researchers working in tandem with keen home gardeners over the past eight years.

Happily the VegeSafe team offers solutions so that people can “Carry On Gardening” (for people seasoned enough to remember the British Carry On comedy films), an axiom dreamed up by project lead Prof Mark Taylor from Macquarie University.

“So the objective was not to be like a set of comedians obviously,” he says in his lilting northern England accent reminiscent of the Beatles. “The motto is to help people carry on gardening but in a safer, better informed way that minimises any potential exposure risk from the evidently quite clear hazard in people’s gardens – elevated soil lead.”

It’s well established that there is no safe level of human exposure to lead (Pb) – which accumulates once in the body – especially for children. Health impacts of lead poisoning have been found in every body organ studied, interfering with brain development and function, the kidneys and heart, blood, immune system and reproduction.

Soil levels in urban areas are largely residues from leaded petrol, which emitted more than 240 tonnes into the atmosphere before it was phased out in Australia by 2002, and weathered, degraded lead paint that was used on old buildings.

“So what we’re looking at really is a legacy,” says Taylor. “There’s some places where it’s contemporary, like emissions to the atmosphere at Mount Isa, Broken Hill and Port Pirie, but when we’re talking about major cities of Sydney, Melbourne, Brisbane, the contamination that we measure in people’s gardens is legacy contaminants.

“I mean, people can recontaminate if they go out and break up batteries in the yard and do smelting and stuff like that, but hardly anyone does that.”

VegeSafe originated because concerned people regularly contacted the researchers to ask if their soil was contaminated and their vegetables safe to eat. The team used a university grant to buy a portable X-ray fluorescence (pXRF) spectrometry instrument which enables rapid testing of trace elements.

“Once we had the machine, there were no analytical costs, just time costs,” says Taylor. When it launched the program in 2013 it was a resounding success. Eight years on and it’s now gathered and analysed – thanks to community donations – a record 20,000 samples from more than 5,000 homes.

Results from more than 3,600 gardens, published recently, revealed that 35% had soil lead levels exceeding the Australian maximum guideline of 300 milligrams a kilogram.

Through questionnaires, the team identified four key factors that could raise alarm bells: proximity to the inner city, age of the house, construction materials and old paint.

To confirm, or gain peace of mind, people can still send soil samples to VegeSafe – following instructions on the website – for free analysis. You can also investigate levels in your area by visiting Map My Environment.

It should be noted that veggies soak up different levels of trace minerals – those that absorb the most, including lead – are leafy greens.

And bear in mind that there might be other imposters lurking in your garden.

“I think contamination extends so far beyond lead in soil,” says Millie Ross, senior researcher and presenter with Gardening Australia. “I think most people would be shocked if they knew what chemicals were applied to their public parks and food.” Pesticides were even found recently in commercial compost.

Unfortunately that’s not as easy to measure as trace metals, but it’s something Taylor is considering and could be in the pipeline through collaboration with a local lab.

So what to do to keep your veggie patch safe? Getting clean soil and mixing it with clean compost is a great start – and if you want to test those for lead you can also send samples to the VegeSafe team.

Garden beds are a good way to start, with a geotextile fabric on the bottom. “Raised beds, clay caps, potted gardens can all help to minimise contact with soil,” says Ross. “Start again,” adds Taylor “and it makes a feature anyway – looks great.”

Other precautions include not mowing the lawn too short because it creates dust that can get into the house or be transferred hand to mouth by little ones. Use a doormat and leave shoes outside so contaminated soil doesn’t migrate inside.

Most importantly, Taylor says: “There’s lots of simple things that people can do to carry on using the garden because the benefits of gardening and getting outside and doing all that far outweigh the risks.”

The success of the project – a shining example of engaging and benefiting the public through science – didn’t elude the Gardening Australia team, who even got Taylor to don a cowboy hat and wield his mighty machine for a segment on the show.

“This work has been so valuable,” says Ross, “mapping the extent of contamination but also providing a really accessible way for gardeners to get information about their own patch.”