FACTORS AFFECTING THE AMOUNT OF LEAD IN HOUSE DUST IN BROKEN HILL

BackgroundLead is widely distributed in Broken Hill soils. As the town has a dry and often windy climate, lead is continuously redistributed in the form of storm water runoff and dust. Given that most residences are within 4 kilometres of mining activity, and many houses are old and often poorly sealed, there is considerable risk of lead bearing dust entering houses. This dust poses a health risk to resident children.Aim of the studyThis study was undertaken by the Broken Hill Environmental Lead Centre (ELC) to identify some of the factors which affect the amount of lead dust entering Broken Hill houses.How we collected the informationThe study was carried out during October and November 1995, as this is usually the windiest period of the year. Therefore, it is thought that the maximum amount of dust enters houses at that time of year.One hundred and sixteen houses were involved in the study. These houses were in all areas of town, and were built of all types of material (wood and iron, brick, stone, etc.). Small plastic dishes (petri dishes) were used to collect indoor dust for periods of about 7 weeks.ResultsThere are no health-based guidelines with which to compare the results of this study. However, the results were compared with a similar study undertaken in Newcastle. Overall, it was found that Broken Hill houses have higher amounts of lead dust than houses in Newcastle, with about 4 times the amount of lead dust fallout. Broken Hill house dust had about 5 times the amount of lead found in Newcastle dust.The study found that the location of the house, the type of house and how well the house was sealed all had a significant effect on results.

  • Location of the house: Houses furthest away from the Line of Lode had the least lead dust. This may be because they are furthest away from the ore body and associated mining and smelting waste. Alternately, it may be because houses closest to the Line of Lode tend to be the oldest are therefore more difficult to keep well sealed. Houses far to the south of the Line of Lode had about the same amount of lead dust as did houses far to the north of the Line of Lode (Figure 1). House type: Wood and iron houses had more lead dust than stone or brick houses. This may be because the wood and iron houses tend to be older than other types of houses, or because dust in their wall and ceiling cavities is more likely to be disturbed during windy periods (Figure 2).Condition of the house: Very well sealed houses had less lead dust than adequately sealed houses, and much less lead dust than poorly sealed houses (Figure 3). This was true even for houses located close to the Line of Lode.
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    ConclusionsThe study suggests that sealing a house substantially reduces the amount of lead in the indoor dust, regardless of where the house is located. This seems to imply that sealing houses removes a specific lead exposure pathway. It is considered that ceiling dust entering the house might be this exposure pathway, as ceiling dust is very fine and generally much higher in lead than the surrounding soils in the yard.