Zinc in House Dust: Speciation, Bioaccessibility, and Impact of Humidity
- DOI
- Language of the publication
- English
- Date
- 2014-07-21
- Type
- Article
- Author(s)
- Beauchemin, Suzanne
- Rasmussen, Pat E.
- MacKinnon, Ted
- Chénier, Marc
- Boros, Kristina
- Publisher
- American Chemical Society
Abstract
Indoor exposures to metals arise from a wide variety of indoor and outdoor sources. This study investigates the impact of humid indoor conditions on the bioaccessibility of Zn in dust, and the transformation of Zn species during weathering. House dust samples were subjected to an oxygenated, highly humid atmosphere in a closed chamber for 4 to 5 months. Zinc bioaccessibility before and after the experiment was determined using a simulated gastric acid extraction. Bulk and micro X-ray absorption structure (XAS) spectroscopy was used to speciate Zn in dust. Exposure to humid conditions led to a significant increase in Zn bioaccessibility in all samples, which was due to a redistribution of Zn from inorganic forms toward the organic pools such as Zn adsorbed on humates. ZnO readily dissolved under humid conditions, whereas ZnS persisted in the dust. Elevated humidity in indoor microenvironments may sustain higher Zn bioaccessibility in settled dust compared to drier conditions, and part of this change may be related to fungal growth in humid dust. These results help to explain the greater bioaccessibility of certain metals in house dust compared to soils.
Plain language summary
Health Canada is investigating the extent to which Canadians are exposed to metal compounds in residential environments. As children spend the majority of their time indoors, it is important to understand factors influencing metal exposures in the indoor environment, including indoor and outdoor sources of metals and the influence of household characteristics (such as humidity). This study, which was conducted in collaboration with Natural Resources Canada, investigated whether humid indoor environments (such as a damp carpet or a window well during winter months) cause zinc to become more bioaccessible (available for biological uptake) in indoor dust than in outdoor soil. Laboratory experiments were conducted to determine if zinc compounds in dust undergo transformation to more soluble forms, when exposed to high moisture levels that may be found indoors The solubility of zinc in the dust samples was measured in simulated stomach acid before and after 4 months of exposure to these humid conditions. Zinc solubility increased in all dust samples. Detailed X-ray analysis showed that exposure to humidity caused inorganic compounds like zinc oxide to actually transform into more soluble compounds such as Zn adsorbed on organic matter. These results help to explain the greater bioaccessibility of certain metals in house dust compared to soil, and contribute to Health Canada's risk assessment and risk management activities under the Chemicals Management Plan by filling knowledge gaps related to human exposure assessment.
Subject
- Health,
- Health and safety