The Critical Role of House Dust in Understanding the Hazards Posed by Contaminated Soils

Factors affecting lead and cadmium levels in house dust in industrial areas of eastern Germany

The indoor exposure of 381 women (52-59 years old) to lead and cadmium was assessed by measuring the levels of the contaminants in sedimented house dust. The study was conducted in the areas surrounding the towns of Hettstedt, a region of mining and smelting of non-ferrous ores, of Bitterfeld, a centre of chemical production and coal mining, and of Zerbst, a primarily agricultural area. Factors that were significantly associated with lead and cadmium surface loading rates included the city area of residence, urban environment of dwelling, ventilation behaviour, type of heating, year of construction of building and crowding in the sampling room. In metal-contaminated areas, the transport of heavy metals into the home from external sources and their subsequent resuspension into the air due to normal household activities are significant factors in the exposure to heavy metals, whereas in unpolluted areas indoor sources play the major role.

Factors affecting lead, cadmium, and arsenic levels in house dust in a smelter town in eastern Germany

Hettstedt, a city in eastern Germany with a long history of mining and smelting of nonferrous ores, has several industrial sources of heavy metals. The indoor exposure to metals of children (5 to 14 years old) in the Hettstedt area was assessed by measuring the levels of lead, cadmium, and arsenic contamination in sedimented house dust. Factors which influence the dust loading rate and the surface loading rates of these contaminants in house dust were investigated. The geometric mean of the dust loading rate was 8.9 mg/m2 day. The geometric means of surface loading rates were 1.14, 0. 024, and 0.023 microg/m2 day for lead, cadmium, and arsenic, respectively. Factors that were significantly associated with surface loading rates included the city area of residence, automobile traffic near home, parent with occupational exposure to heavy metals, type of heating, housing characteristics, whether child's home is damp, number of persons living in the child's home, and parents' education. The most significant of these factors was the city area of residence, which reflects the distance from the metal sources; this factor accounted for about half of the variances explained by the regression models.

Hazard identification and risk assessment of pyrethroids in the indoor environment

Household insecticide products raise several important considerations concerning safety. These are related to the use of insecticides by untrained individuals, the difficulty of controlling the use of these products once purchased by the consumer and the potential exposure of the very young and very old, possibly with or without pre-existing pulmonary disease. Exposure to pyrethroids contained in mats or vaporizers, being slow release systems, have particular potential for long-term low-level exposure whilst for foggers, spray-cans or sprayed formulations the short-term high-level exposures may be of more concern. According to the volatility of the active ingredient contained in the household insecticide, its persistence in a non-inhalable matrix, i.e. sedimented house dust, may be short or long for highly volatile or low volatile active ingredients, respectively. On the other hand, the potential of exposure is apparently just reciprocal. This demonstrates that the extent and duration of exposure may be highly product-specific. Accordingly, the extent of exposure has to be accounted for and for risk assessment both concentration-dependent (e.g. sensory irritation) as well as concentration x time (= dose) related effects have to be considered and addressed in adequate bioassays. The issue as to whether pyrethroids adhering to house dust is of concern has been addressed in a model study using carpets treated with pyrethroids. This study has demonstrated that the total mass of pyrethroid applied to the carpet and that brushed off within an 18-h period is too small to be of any relevance for risk assessment. Therefore, assessment of health hazards in the indoor environment based simply on methodologies of emptying the household vacuum cleaner and analysing its content, which addresses contamination only, rather than examination of the actual airborne concentration, including other relevant airborne materials, is prone to tremendous errors and misjudgments. Due to the many substances potentially present in house dust and indoor air, e.g. bioaerosols originating from animals, pests and microorganisms, volatile organic substances (VOCs) or metals, prudent expert judgment is needed to assess the relevance of analytical findings. The complex indoor exposure scenario makes it especially difficult to causally relate clinical and epidemiological findings to arbitrarily selected indicator substances contained in a matrix not readily available to inhalation exposure.