Antimony (Sb) in PET Bottles

In a recent press release, the University of Heidelberg reported that Prof. William Shotyk and co-workers at the Institute of Environmental Geochemistry, University of Heidelberg, measured the abundance of antimony in fifteen brands of bottled water from Canada and forty-eight from across Europe

Bottled waters in PET containers are contaminated with antimony (Sb), a potentially toxic heavy metal with no known physiological function. Antimony trioxide is used as a catalyst in the manufacture of PET (polyethylene terephthalate), and PET typically contains several hundred mg/kg of Sb. For comparison, most of the rocks and soils at the surface of the earth contain less than 1 mg/kg Sb.

Prof. William Shotyk and co-workers at the Institute of Environmental Geochemistry, University of Heidelberg, measured the abundance of Sb in fifteen brands of bottled water from Canada and forty-eight from across Europe. His team also measured Sb in a pristine groundwater from a rural region of Canada, three brands of deionized water in PET bottles, as well as a new brand of water from Canada bottled commercially in polypropylene. Measuring Sb in pristine waters is quite a challenge because of the very low natural abundance of this element. This was not a problem for Dr. Michael Krachler, a leading expert for the analysis of Sb in environmental samples. Dr. Krachler used the unique clean laboratory facilities available at the University of Heidelberg which had earlier allowed him to measure Sb in polar snow and ice from the Canadian arctic.

The pristine groundwater was found to contain only two parts per trillion of Sb, with the bottled waters typically showing values a few hundred times greater. The water in polypropylene was comparable to the pristine water, 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. Adding pristine groundwaters to PET bottles quickly confirmed that the bottles were contaminating the waters by leaching of Sb from the containers.

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 360 parts per trillion. This same brand of water in PET bottles, but purchased three months earlier, yielded 630 parts per trillion Sb.

Although all of the waters tested were found to contain Sb in concentrations well below the guidelines commonly recommended for drinking water, Shotyk said that the continuous release from the container to the fluid is bothersome. "There is unlikely to be a beneficial effect of Sb contamination". He noted further that in Japan, PET is manufactured using titanium (Ti), an element which is effectively insoluble and harmless, instead of potentially toxic Sb.

In order to put the findings into a regulatory and quantitative context it is important to note that:

• To put "parts per trillion" into perspective, one part per trillion can be considered equal to one second in 32,000 years
• 1000 parts per trillion (ppt) equals 1 part per billion (ppb)
• The World Health Organization has established a drinking water level of 20 ppb (20.000 ppt) and the European Food Safety Authority has established a migration limit of 40 ppb (40.000 ppt) antimony in food.
• 5 or 6 ppb (5.000 – 6.000 ppt) have been established for drinking water in the US, Canada, and Europe and are substantially higher than the levels found in the Heidelberg study.
• Water in glass contains up to 30 times less antimony than water packaged in PET