Think before you drink: antimony contamination from Arctic snow to bottled water.
Antimony is a fascinating element for a number of reasons:
* the antiquity of its discovery and use;
* its remarkable history in alchemy and early medicine;
* the number of modern industrial processes that employ it;
* the extremely broad range of high technology materials that contain it;
* the diversity of its chemical behaviour.
With respect to the predominant sources, biogeochemical behaviour, and the ultimate fate of Sb in the environment, there have been remarkably few studies compared to other potentially toxic metals such as mercury (Hg), lead (Pb), cadmium (Cd), or arsenic (As).
Increasing concentrations, enrichments, and accumulation rates of Sb in peat bogs from Europe have shown that emissions of atmospheric Sb has increased dramatically since the beginning of the Industrial Revolution. Peat cores from bogs can be used to reconstruct atmospheric Sb deposition extending back in time many thousands of years. Peat samples from European bogs show that emissions of Sb have largely evolved parallel to those of Pb since the Roman Period, indicating the intensity and long history of atmospheric Sb contamination. Why has atmospheric Sb contamination resembled that of Pb for two thousand years? Lead ores are commonly enriched in Sb, thus mining and smelting of lead ores has not only emitted Pb into the environment, but Sb also. Atmospheric Sb contamination is so extensive, even peat bogs from remote locations such as the Faroe Islands reveal atmospheric Sb contamination dating from the Roman Period. These findings suggest that the environmental impact of human activities on the Sb cycle are comparable to those of Pb.
To determine whether or not Sb, like Pb, is a global contaminant, Krachler and I teamed up with Jiacheng Zheng and David Fisher of the glaciology division of the Geological Survey of Canada. Using ice cores from Devon Island (75[degrees] N) that extend back in time more than 15,000 years, Krachler and Zheng analyzed the samples using the unique clean lab and ICP-SMS facilities in Heidelberg, creating the first complete time series for atmospheric Sb in the Arctic. Unlike Pb, which has been declining during the past three decades, the enrichment of Sb during the same interval has increased approximately 50 percent. Scandium, also measured for the first time in polar ice, served as a reference element, and provides an index of the natural Sb inputs from soil dust and other mineral particles. Analyses of the ancient ice samples provide a measure of the "background" inputs of Sb to the Arctic, clearly showing that natural atmospheric Sb inputs to the Arctic today are dwarfed by industrial emissions. The magnitude of the Sb enrichments in snow and ice from a remote region of the Arctic indicates that this element, like Pb and Hg, truly is a global contaminant.
Although Sb is mainly used today as a flame retardant in textiles and plastics, it has numerous other industrial applications, including in alloys with lead to harden car batteries as well as bullets, and in brake shoe pads. Imagine this the next time you are driving your car--each time you use your brakes, submicroscopic particles rich in Sb are abraded from the brake pads and released into the air. Analyses of aerosols from Tokyo, Japan, by Naoki Furuta and his colleagues at Chuo University show that Sb is now the most highly enriched trace element in the PM2.5 fraction. Antimony trioxide is a suspected carcinogen and is considered a priority pollutant by the U.S. EPA, the E.U., and the German Research Foundation (DFG).
Antimony trioxide is used as a catalyst in the manufacture of PET. PET typically contains several hundred mg/kg of Sb. For comparison, the abundance of Sb in crustal rocks at the surface of the earth is typically on the order of one mg/kg or less. My colleagues and I measured the abundance of Sb in 15 brands of bottled water from Canada and 48 from across Europe. Our team also measured Sb in pristine groundwater from a rural region of Canada (Springwater and Tiny Townships, in Simcoe County, ON), three brands of deionized water in PET bottles, and a new brand of water from Canada bottled commercially in polypropylene. Measuring Sb in pristine waters was not possible in the past, using conventional analytical methods, because the natural abundance is generally far below the detection limits provided by traditional approaches. Having measured Sb in polar snow and ice, it was not difficult for Krachler, using the laboratory facilities available at the University of Heidelberg, to measure Sb in groundwater.
The pristine groundwater was found to contain only two parts per trillion of Sb, and the bottled waters from Canada and Europe typically showed values a few hundred times greater. The water in polypropylene was comparable to the pristine water as shown in Figure 1, suggesting that the PET bottles were to blame for the high Sb values. Even though deionized water should be very clean, in PET bottles these contained as much Sb as the natural waters in PET bottles. So, the deionized tap waters being sold in PET bottles contain as much Sb as the natural waters being sold in PET containers. Adding pristine groundwaters to PET bottles quickly confirmed that the bottles were contaminating the waters by the leaching of Sb from the containers.
[FIGURE 1 OMITTED]
Comparison of three German brands of water available in both glass bottles and PET containers showed that waters bottled in PET contained up to 30 times more Sb. As a final test of the contamination hypothesis, water was collected from a commercial source in Germany prior to bottling. This water was found to contain only four parts per trillion of Sb. However, the same brand of water purchased locally in PET bottles, was found to contain 560 parts per trillion. This same brand of water in PET bottles, but three months older, yielded 630 parts per trillion Sb. Clearly, the concentration of Sb in bottled water is effectively independent of the natural abundance, but dependent on the duration of storage in the PET container.
Although all of the waters tested were found to contain Sb in concentrations well below the guidelines commonly recommended for drinking water, the continuous release from the container to the fluid suggests that further studies are warranted. Acidic beverages in PET containers should be even more susceptible to leaching. Given that Sb has no physiological function and is a cumulative toxin, there is unlikely to be a beneficial effect of the Sb contamination. The environmental fate of Sb in waste streams, especially from Sb-containing textiles and plastics, also deserves attention.
N. Furuta, A. Iijima, A. Kambe, K. Sakai, and Sato, K. "Concentrations, enrichment and predominant sources of Sb and other trace elements in size classified airborne particulate matter collected in Tokyo from 1995 to 2004," Journal of Environmental Monitoring 7 (2005), pp. 1155-1161.
M. Krachler, J. Zheng, C. Zdanowicz, R. Koerner, D. Fisher, and W. Shotyk, "Increasing enrichments of antimony in the arctic atmosphere," Journal of Environmental Monitoring 7 (2005), pp. 1169-1176.
W. Shotyk, M. Krachler, and B. Chen Contamination of Canadian and European bottled waters with antimony leaching from PET containers. Journal of Environmental Monitoring 8 (2006), pp. 288-292.
W. Shotyk, M. Krachler, and B. Chen, "Antimony: Global Environmental Contaminant," (Guest Editorial). Journal of Environmental Monitoring 7 (2005), pp. 1135-1136.
W. Shotyk, M. Krachler, B. Chen, and J. Zheng, "Natural abundance of Sb and Sc in pristine groundwater, Springwater Township, Ontario, Canada, and implications for tracing contamination from landfill leachates," Journal of Environmental Monitoring 7 (2005), pp. 1238-1244.
W. Shotyk, B. Chen, and M. Krachler, "Lithogenic, oceanic, and anthropogenic sources of Sb to a maritime blanket bog, Myrarnar, Faroe Islands," Journal of Environmental Monitoring 7, (2005) pp. 1148-1154.
W. Shotyk, M. Krachler, and B. Chen, "Anthropogenic impacts on the biogeochemistry and cycling of antimony," in "Biogeochemistry, availability, and transport of metals in the environment," Vol. 44 of Metal Ions in Biological Systems, A. Sigel, H. Sigel, and R. K. O. Sigel, eds. (New York: M. Dekker), pp. 172-203.
William Shotyk received his BSc in soil science and chemistry front the University of Guelph in 1981, a PhD in geology from The University of Western Ontario in 1987, and a habilitation in geochemistry from the Universitat Berne, Switzerland, in 1995. Since October of 2000, he has been professor at the University of Heidelberg (C4) and director of the Institute of Environmental Geochemistry. His research group is responsible for inorganic and radiogenic isotope geochemistry. His main research interests focus on human impacts on the exogenic geochemical cycles of potentially toxic trace elements.
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|Comment:||Think before you drink: antimony contamination from Arctic snow to bottled water.|
|Publication:||Canadian Chemical News|
|Date:||May 1, 2006|
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