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Vegesafe

Latest findings

 

August 2017

VegeSafe has provided soil metal information to more than 1700 (and counting) households across Australia, and is by far the largest study of its kind in Australia. From our results, it is clear that the contaminant of most concern across backyards in major cities is lead.

Typical 'natural' or 'background' concentrations of lead in most parts of Australia lie within 20-30 mg/kg (or parts per million). However, due to the intense use of lead-containing products such as lead-based paints and leaded petrol over the last century, many residences, especially in larger urban centres, have been contaminated with lead.

Research from our recent paper of Sydney homes (Rouillon et al. 2017) found that 40 % of residences sampled exceed 300 mg/kg of lead in garden soils (the Australian guideline for domestic residences). Many homes growing food were doing so in lead-contaminated soils (Figure 1). The consistently high lead concentrations in the older, inner city and inner west areas were evident across all four garden soil locations sampled, those being front yard, drip line, back yard, and vegetable gardens (Figure 2). Soils from older homes that have painted exterior surfaces are most likely to be contaminated with lead due to a longer time to accumulate lead over the years, a greater likelihood that they were painted with lead-based paints, and a greater chance that this paint has deteriorated naturally (due to the elements) or were improperly removed, further contaminating garden soils (Figure 3).

Sydney residences had a mean soil lead concentration of 415 mg/kg - while the 'background' level of soil lead from homes that are >40 km from the CBD, were less than 30 mg/kg.

The highest soil lead in this study was over 6000 mg/kg, that is over 200 times more lead that the references homes >40 km from the CBD.

               

Figure 1: Soil lead concentrations of vegetable garden soils where people grow their food. The older, inner city and inner west suburbs of Sydney have the greatest soil lead concentrations, largely due to contamination from leaded petrol and lead-based paint sources.

               

Figure 2: Soil lead concentrations across all four garden soil types in the study of Rouillon et al. 2017. Soils were tested from Front yards, Drip lines, Back yards and Vegetable garden locations.

 

Figure 3: Median soil lead concentrations across a typical Sydney residence for four categories of dwellings: Pre-1970 homes painted homes, Pre-1970 non-painted homes, Post-1970 homes and reference homes (>40 km from CBD). This figure shows a clear effect of age, and the presence of paint on median soil lead at Sydney properties. For homes built before 1970, the greatest concentrations of lead were found at Drip line locations. This is because lead-based paints and leaded petrol emissions commonly become deposited here due to proximity to the painted walls where lead paint can flake off, and/or the accumulation of air pollution due to a structure halting the momentum of air particles, hence they fall and deposit onto the base of buildings.