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. READ MORE: "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.