A recent study to update information about soil contamination in parts of Hobart has supported advice that the metal levels in soils still pose only a low health risk to residents.
A new round of testing has shown that metal levels have not significantly changed in the past ten years and that health studies and advice provided at that time remain current.
However, the new study has resulted in reduction of the area where metal levels are above investigation levels and where precautionary advice applies.
Past activities at the Hobart zinc smelter have resulted in elevated levels of metals in surface soils in parts of Lutana, Geilston Bay and Lindisfarne.
Previous sampling in the 1990s found that the surface layer of soil in parts of these suburbs contained elevated levels of zinc, lead and cadmium. The primary cause of the contamination was identified and ceased in the 1990s.
Last year, the Environment Protection Authority (EPA) and Nyrstar agreed on the need for a new soil sampling survey in the affected areas to enable public information on the issue to be updated.
"This latest study has found that overall, the concentration of lead and cadmium is not significantly different to previous surveys carried out in the 1990s," EPA director Warren Jones said.
"Nevertheless, wider sampling and the use of modern surveying and analysis techniques has enabled a more precise definition of the boundary of the area affected.
As a result, the area where metals levels are above national investigation levels has been revised and reduced," Mr Jones said.
Rose Bay and the southern area of Lindisfarne are no longer in this area.
While primarily due to the better techniques used in the study, the reduction of the affected area was, in part, also due to the lowering of levels of metals in surface soils at selected sites.
A CSIRO review of the historic and recent sampling programs has found that the programs were ‘robust, and that the data can be considered precise and accurate.’
The CSIRO review also noted that the scientific techniques used to define the affected area were appropriate.
The State Manager of Environmental Health Services within the Department of Health and Human Services, Stuart Heggie, said the main pathway for exposure is direct contact with the contaminated soil and through high consumption of vegetables grown in the soil – particularly leafy greens.
"While the most recent testing shows that these elevated levels of metals in the soil still exist, previous measurements of actual human exposure to these contaminants have indicated that health risks are small," Mr Heggie said.
"For example, in 1997 the average blood lead levels in children in the affected area had fallen to half the levels found in a previous survey in 1991, and were slightly lower than the national average at the time."
However, Mr Heggie said residents could further reduce their exposure risk by taking the following precautionary measures:
- covering bare soil with grass, mulch or pavers;
- washing soil and dust from children’s hands frequently;
- growing home-grown vegetables, particularly leafy greens, in raised beds with new clean soil at least 30cm in depth;
- thoroughly washing dust and soil from home-grown fruit and vegetables;
- frequently washing dust and soil from children’s toys and the family
- keeping the house dust-free through regular cleaning of window sills and other dust-prone areas.
The precautionary measures are outlined in an information bulletin being sent to householders in the contaminated area. It updates a similar information bulletin produced and distributed in 1999.
The advice will also be passed on to new residents in the area by the Glenorchy and Clarence City Councils, who will place an alert on the section 337 certificate issued by Council during the conveyancing period.
"The current brochure is an update of similar information produced in 1999," Mr Jones said.
"The new information brochure will be sent to householders who received the previous bulletin. Some of them now sit outside the revised boundary area but we thought it was important to update them on the latest sampling."
Individuals who have particular concerns about soil contamination can contact the Environment Protection Authority or the Department of Health and Human Services.