Dangerous levels of lead linked to Aussie gardens

An alarming new study has suggested spending time in the veggie patch could be putting your health at risk.

The research, led by RMIT University and published in the Chemosphere Journal suggested that as many as one-in-five Melbourne backyard veggie patches contain levels of lead that exceed the limit recommended by the Health Investigation Level.

Researchers analysed 136 vegetable gardens across Melbourne’s metropolitan area and found that 21 per cent of soil contained more that 300mg of lead per kilogram. These high levels have prompted the Human Investigation Level to start an investigation to figure out what’s going wrong. A further 13 community gardens were also tested, with 8 per cent of those with lead above the recommended guideline.

The study was led by RMIT Associate Professor Suzie Reichman and Dr Mark Laidlaw, who suggested that houses built before the 1970s could be to blame due to high volumes of lead-based paint used on the outside of older homes.

“The older the house, the more lead generally found in the garden soil,” Professor Reichman told Starts at 60. “We found that the concentration of lead in soil was higher in painted homes, and in soil underneath the dripline.”

She urged homeowners to test the soil in their gardens as soon as possible if they’re concerned. 

Researchers couldn’t determine why levels of lead were different between backyard and community gardens – all of which were within 10km of the Melbourne central business district. They did suggest vegetables found in community gardens were grown in raised beds that contained imported clean soils or soil amendments, which could explain the difference. “Also, none of the community gardens tested were located near the two main sources of lead contamination in urban soils – main roadways and structures containing exterior lead-based paint,” Reichman added.

A similar study from 2017 found that 40 per cent of Sydney gardens had lead levels greater that 300mg/kg and warned that it could also be an issue for other parts of the country.

“The main factors affecting lead concentrations in soils are age of house and if the house is painted, proximity to major roads and proximity to industry,” she said. “So anywhere around Australia that had one or more of these risk factors is likely to have elevated lead concentrations,” Reichman said. 

Read more: Simple tips to make gardening easier on the body

About 48 per cent of Australians now grow fruit and vegetables from their own garden. Lead can cause harm to everyone, but young children and unborn babies are most at risk.

The research team outlines a series of recommendations to help people protect themselves and their gardens from lead. The first is to grow vegetables in raised beds using clean, imported soil. Certain vegetables such as lettuce, carrots, onions, turnips and radishes are more likely to be lead accumulators, so limiting the growth of these vegetables is recommended.

Where possible, professionals should be used to safely remove faking exterior of lead-based paint from homes to prevent further contamination, while gardeners should avoid growing in nature strips near roadways as lead levels can be higher in these areas.

Any fruit or vegetables grown should always be washed thoroughly to ensure that soil and any potential traces of lead are removed. 

Reichman concluded that the research wasn’t intended to scare people, but rather educate them of this potential problem.

“I don’t think anyone should stop gardening because of our study, rather I hope that our research informs people so that they can ensure they are gardening safely,” she said. “I suggest they get their soil tested.”

Macquarie University runs a citizen science program called Vegesafe that provides metal concentrations in up to five samples.  You can also send your soil to a commercial laboratory if you prefer.

What do you think? Are you concerned your garden could be contaminated with lead?