Growing vegetables in your garden at home is a popular pastime for many Melburnians. But just how much do you know about metal contaminants in the garden bed soil?

A new study of soil metal concentrations in residential and community vegetable gardens found soil in some Melbourne home gardens had elevated levels of lead.

"In certain circumstances, the data indicates that elevated soil lead concentrations could present a potential health hazard in a portion of inner-city residential vegetable gardens in Melbourne," researchers said.

The study, a joint project between RMIT University and Macquarie University, was published in February and analysed soil samples from 136 home vegetable gardens across Melbourne.

In 21 per cent of those samples, the mean soil lead concentration exceeded 300 mg/kg, which is the Australian residential health investigation level (HIL).

"Soil lead concentrations were higher in homes with painted exteriors, generally increased with age of the home, and were higher beneath the household dripline than in vegetable garden beds," the report finds.

The researchers said it was the first time an assessment like this had been done for home gardens in Melbourne.

House age, paint impact on lead levels

One of the researchers, Associate Professor Suzie Reichman from RMIT University, said the study showed a trend towards lead levels in soil being higher in inner-city suburbs.

"We mostly found it related to the house age and whether the houses had been painted, and that is because of the historical use of quite high concentrations lead in paint," she said.

"Also, some houses are close to major roads, and we used to have leaded petrol and the emissions from vehicles fall on roofs, and then when it rains they get washed down and some of it ends up in the soil."

Mean soil lead concentrations in residential vegetable gardens of Melbourne. ( Supplied: RMIT University )

Dr Reichman said households could commission soil tests, and if the results showed a reading above the investigation level, it did not mean the soil was toxic — but that it could be.

"If it was a commercial setting they would do a full risk assessment, but for home gardens that is not really practical, it is too expensive," she said.

"If home gardeners have lead concentrations above the 300mg/kg level, they might want to get some of their veggies tested to see if they have elevated levels of lead or take a precautionary approach, like use raised garden beds and import good quality soil from reputable sources."

Roots absorb more metals than other veggies

Macquarie University's community science participation program VegeSafe can test metal levels in vegetables and RMIT University is working to set up a program.

Dr Reichman said root vegetables absorbed metals more readily than other vegetables.

"Also, if you are digging those veggies out from the soil, even if you clean them really well there is a good chance you will be directly eating a bit of the contaminated soil," she said.

Raised garden beds with clean imported soil can help reduce lead levels. ( ABC News: Sally Brooks )

The study — titled Assessment of soil metal concentrations in residential and community vegetable gardens in Melbourne, Australia — concluded more assessment was needed of the risks associated with excess lead in garden soils.

"This was a relatively limited study, there are over a million households in Melbourne and we only had about 130 houses we were able to sample and we were only able to sample about a quarter of the community gardens," Dr Reichman said.

"So it's a great start but it's hard to see patterns across Melbourne and give people really clear information about what the risks to their garden is for the concentration of lead or potentially other metals."