|LEAD Action News vol 11 Number 2, December
2010, ISSN 1324-6011
Incorporating Lead Aware Times (ISSN 1440-4966) & Lead Advisory Service News (ISSN 1440-0561)
The journal of The LEAD (Lead Education and Abatement Design) Group Inc.
Guest Editor, Dr Chrissie Pickin. Editor-in-Chief: Anne Roberts
How does Rosebery compare with other Australian mining towns?
By Rosalind Harrison, Toxicologist, DHHS, Tasmania
The allegations of heavy metal poisoning in Rosebery have focussed attention on the effects of mining on the wider community, not just in the Tasmanian town, but across the nation.
Tasmanian health authorities say while there is no acknowledged safe level of lead, the aim is to reduce exposure and absorption to an absolute minimum for everyone. But, they maintain that in reality, many Australian mining areas would strive to have the levels of community results recorded in Rosebery.
Mining activities can result in the production of mine tailings waste and airborne releases of metals – both of which represent a source of exposure to the non-mining community. In addition, occupationally exposed workers can inadvertently contaminate the home environment, resulting in potential exposure to family members (Chiaradia et al 1997).
Lead is a widespread naturally occurring metal. It can be found in increased concentrations in some areas through natural mineralisation. Other environmental sources include lead mining and smelting, and activities such as the breaking down of lead batteries for recycling. Young children are particularly susceptible to the effects of metals for two main reasons. Firstly, they are more likely to eat or chew on non-food objects e.g. soil, and frequently suck their hands and fingers. Secondly, children have a higher absorption rate of metals from the gastrointestinal tract (Meza-Figueroa et al 2009). It is generally accepted that measuring the concentration of lead in blood is the best indicator of exposure to lead (NHMRC 2009). The blood lead level is reported as micrograms (µg) of lead per decilitre (dL) of blood (µg/dL). Preventive measures can then be taken to reduce or remove exposures to individuals with high blood lead levels. Based on the scientific evidence on the effects of low-level exposure to lead, it is not possible to make a definitive statement on what constitutes a ‘safe level’ for blood lead concentrations. This is the view of the National Health and Medical Research Council (NHMRC) as well as other international organisations. The NHMRC recommends that all Australians should have a blood lead level below 10 µg/dL (NHMRC 2009).
Mining in Australia dates back to European settlement at the end of the 18th Century, with the discovery of coal in NSW (ABS 2001). Lead was the first metal mined in Australia – in 1841 at Glen Osmond near Adelaide.
The world famous gold rushes of the 1850s resulted in people migrating to Australia. During the gold rushes, Australia was producing almost 40% of the world’s gold (ABS 2001, Mining History 2010, Australian Mine Atlas 2010).
In the early years of the 20th Century, mining activity in Australia began to decline. The next discovery was the lead, zinc and silver deposit at Mount Isa, where mining and smelting commenced in 1931. From the late 1940s, mining in Australia began to expand, with the discovery of mineral resources and the investment of overseas mining companies (ABS 2001, Mining History 2010, Australian Mine Atlas 2010).
Today, the minerals industry is a major contributor to Australia’s export trade. A wide variety of minerals are extracted across all states and territories, including bauxite, aluminium, diamond, lead, ilmenite, rutile, zircon, coal, zinc, gold, iron ore, manganese, nickel, copper, silver, uranium, and opal (Australian Mine Atlas 2010).
Major mining towns in Australia today include Mount Isa (Qld), Broken Hill (NSW), Port Pirie (SA), Coober Pedy (SA) and Kalgoorlie (WA).
The mine at Rosebery is operated by Minerals and Metals Group (MMG). It is an underground mine with 243 employees, and has been in continuous operation since 1936. The mine produces approximately 700,000 tonnes of ore per year through mechanised underground mining methods. The ore is processed into concentrates of zinc, lead and copper. Silver and gold are also extracted from the ore (MMG 2010). Extensive biomonitoring tests were carried out on Rosebery residents and mine workers during the period 1st January, 2008 to the end of April, 2010. 504 adults (392 men and 112 women) and 29 children from Rosebery were tested for lead exposure. The majority of this testing related to the occupational testing of miners. The average level for adults was 7.5 µg/dL, and women specifically had an average level of 2.9 µg/dL. The range of blood lead levels for adults was 1 µg/dL to 30 µg/dL. 116 adults had blood leads, at least at one point in time, over 10 µg/dL, but 111 of these were known to be occupationally exposed. The average level for children was 3.0 µg/dL. This level included the results of two children whose property was contaminated following a concentrate spill. Excluding the average of these two results, the average is reduced to 2.6 µg/dL (compared with 7.04 µg/dL in 1998).
In comparison, blood lead levels in other Australian mining communities are more often elevated, particularly in children. The table below summarises mean blood lead levels for children across Australia from both mining and non-mining communities. Further detail of monitoring surveys carried out across Australia is provided in the text.
Table 1: Comparison of mean blood lead levels (µg/dL) for children from mining and non-mining communities across Australia over the past 26 years
1 Mining community. 2 Non-mining community. 3 Preliminary
unpublished result for 2010
Mount Isa in Queensland is one of Australia’s largest mining and smelting operations, producing lead, silver, copper and zinc. In 2006, Xstrata Mount Isa Mines commissioned the Lead Pathways Study, to better understand the potential pathways of lead into the Mount Isa community through land, air and water. In July, 2009, phase one (land) of the study was completed; concluding that the risk to human health from historical mine sediment is low. Phases two and three (air and water pathways) are due to be completed in 2011 (The University of Queensland 2009, Xstrata 2008). Queensland Health reported that a survey of 400 Mount Isa children aged between 12 and 60 months (approximately 25% of the age cohort in the Mount Isa community) in 2006-07 showed a mean blood lead level of 5 µg/dL, with 11.3% (45 children) having levels greater than 10 µg/dL and 0.5% (two children) exceeding 20 µg/dL. The highest recorded blood lead level was 31.5 µg/dL (Queensland Health 2008). Preliminary results are available from a repeat survey undertaken in 2010 of 167 Mount Isa children. The mean blood lead level was 4.27 µg/dL, with 4.8% (eight children) equal to or above 10 µg/dL and 0.6% (one child) exceeding 20 µg/dL. The highest recorded blood lead level was 22.4 µg/dL (unpublished data, personal communication from Dr GR Neville, Senior Medical Officer, Queensland Health).
In Broken Hill, silver, lead and zinc are mined. In the early 1990s, high blood lead levels (means of 12-16 µg/dL) were confirmed in children aged between one and four years. In 1994, the Lead Management Program was launched to reduce blood lead levels in children. In 2001, the mean blood lead level for children had decreased to 7.6 µg/dL with 64% of children below 10 µg/dL. However, 15% of children still showed significantly elevated blood lead levels (>15 µg/dL) (Burke et al 2003). By 2003, the mean child blood lead level had further reduced to 7.1 µg/dL, with 12% showing elevated blood lead levels (>15µg/dL) (Lyle et al 2006). By 2007, the mean blood lead level had dropped to 5.8 µg/dL; however, one in five children still have blood lead levels higher than 10 µg/dL (Boreland et al 2008, Boreland and Lyle 2009).
The Cockle Creek smelter in Boolaroo was a zinc and lead smelter prior to its closure in 2003. In 1991, lead emissions were controlled and subsequently, child blood lead levels decreased from 11 µg/dL (1991) to 7.5 µg/dL (2000) (Morrison 2003). Since the smelter was closed in 2003, blood lead levels have decreased substantially (Boreland et al 2008).
The Port Pirie lead smelter in South Australia processes lead and zinc ore. Since the early 1980s, high blood lead levels have been a concern in the local community and in 1984, the Port Pirie Lead Implementation Program was established to reduce the blood lead levels of children. In 1984, the mean blood lead level of children aged one to four years in Port Pirie was 22.4 µg/dL with 98% of children exceeding 10 µg/dL. By 2004, monitoring results significantly improved, with a mean blood lead level of 10.6 µg/dL and 60% of children exceeding 10 µg/dL being reported (Maynard et al 2006). During the years 1998-2004, the downward trend reached a plateau with mean blood lead levels and the proportion of children exceeding 10 µg/dL reported to be: 10.4 µg/dL and 59% (1998), 9.8 µg/dL and 55% (2001), and 10.6 µg/dL and 60% (2004), respectively. The Lead Implementation Program not only identified and case managed young children with elevated blood lead levels, but also involved house decontamination, treatment of institutions frequented by young children, soil treatment, city greening, footpath sealing, family education and support, and community education (Maynard et al 2006).
Since 2006, the Department of Health (South Australia) reports the proportion of Port Pirie children (zero to four years) with blood lead levels below 10 µg/dL. Results for 2009 indicate that 72% of the children tested in Port Pirie had a blood lead level below 10 µg/dL – this is an improvement of approximately 23% since 2005 (Government of South Australia 2010a). Interim results for the first half of 2010 indicate that so far this year, 65.7% of children tested had a blood lead level below 10 µg/dL (Government of South Australia 2010b).
In non-mining communities across Australia and around the world, current blood lead levels are similar to those observed in Rosebery. Comparisons of mean blood lead levels in Australian children (less than six years) from urban environments demonstrate levels of 1.83 µg/dL (Fremantle; Guttinger et al 2008); 3.1 µg/dL (Sydney; Gulson et al 2006); and 4.5-5.1 µg/dL (Derby, WA; Mak et al 2003). Similar mean blood lead levels have been observed in children (less than 14 years) around the world: 3.1 µg/dL (Czech Republic; Batariova et al 2006); 1.63 µg/dL (Germany; Kolossa-Gehring et al 2007); and 1.83 µg/dL (Sweden; Stromberg et al 2008).
Rosebery is in a very different situation from other prominent mining communities in Australia, involved with lead production. The Rosebery mine does not have an active smelter producing lead in emissions into the air (which in turn can find its way into surrounding household environments), and does not face quite the same challenges in maintaining low blood lead levels in children. The issue in Rosebery is basically one of a legacy of mild to moderately raised lead levels in soil. Some of this is related to the natural mineralised geology of the region, and in some places there may also be residues from waste ore being used as top fill. Another very important source can also be lead in paint in older housing, and studies on the West Coast have also shown the importance of household hobbies such as car repairs and making fishing sinkers. Good dust management at the mine, hygiene at home, and grass/paving cover of bare dirt will minimise any inhalation exposure to lead.
The crucial issue resulting from the Rosebery investigations is that despite there being evidence of lead contamination in the soil, there is a very low health risk because the blood test results show that little lead is entering the body or being taken up. There is certainly a potential lead hazard in Rosebery, but lead in soil can only cause harm if it gets into the body and is absorbed at a level which causes damage to organs, and this is just not being observed.
However, health authorities say while there are still some people in the at-risk group above 5 µg/dL (one child and seven women of childbearing age), they are not content to leave the issue without further attention, and will strive to reduce the individual and average levels even further.
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Updated 24 January 2012