One-third of backyard vege patches could have toxic levels of lead

Sydneysiders are being warned their veggie patches might be poisoning them.

Toxic levels of lead have been found in gardens across the city - with experts warning the contamination carries major health risks.

Professor Mark Taylor said lead's side effects are numerous, but particularly dangerous for children.

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"The effects would include developmental delays, ADHD behaviours, increased irritability, and poorer executive functioning."

Professor Taylor's recent "VegeSafe" program at Macquarie University found that one-third of backyard gardens across Australia are likely to produce food with unsafe levels of lead.

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"Thirty-five per cent of all gardens... had at least one sample that exceeded the Australian guidelines for lead, which is 300 milligram per kilogram."

Older houses, particularly painted ones, and those in areas with heavy traffic, had even higher readings.

Sydney's inner-city gardens were rated the most toxic, followed by the suburbs of Leichhardt, Marrickville, Ryde, Burwood and Strathfield.

Veggie patches in Liverpool, Merrylands and Canada Bay also recorded high risk lead levels.

Blacktown, Baulkham Hills, Carlingford, Hornsby and Pennant Hills get the green garden tick - those suburbs recorded the lowest amounts of lead.

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But there are things you can do to avoid or lower lead levels.

Using a raised garden bed and fresh soil can help stop contamination, as well as avoiding leafy green vegetables, which absorb more lead from the ground.

Professor Taylor said that he doesn't want to discourage veggie growers - just encourage them to take a little extra care.