Plastic Water Bottles as a Source of the Heavy Metal Antimony
Most single use plastic bottles used to store water and other beverages are made from polyethylene terephthalate (PET) type plastics. During production, PET needs to be polymerized, a process that joins small plastic molecules together into long chains. One of the most common metal compounds used for inducing polymerization is antimony. Due to the demand for the metal, the plastics industry consumes over 60% of the world’s production of antimony (Periferakis 2022).
Beyond its use in plastic bottle manufacturing, antimony is also used as a flame retardant in clothing and textiles. Other industrial uses include as an alloying agent to increase corrosion resistance. As such, antimony is also found in batteries, bullet casings, pipe fittings and bearings.
As a metal, antimony is well known to be toxic. Recommendations vary by country, with safe levels in drinking water being below 2-6 micrograms of antimony per liter.
Due to its use in the production process, PET plastic bottles can contain large amounts of the metal. One study found 213 mg of antimony per kilogram of plastic (Westerhoff 2008). The biggest concerns for leaching antimony from these bottles stem from hotter storage conditions and acidic liquids like soft drinks and fruit juice or alcohol (Westerhoff 2008, Filella 2020).
Does Antimony in Plastic Bottles Pose Any Risks?
The research on how much antimony winds up in beverages from single use bottles is somewhat varied. A recent study in Qatar, where daytime temperatures can be in excess of 50°C (122°F) found that some brands of bottles stored at 50°C for eight months had antimony levels just over 2 micrograms per liter, high enough to start raising concerns (Al-Outum 2017). Even at lower temperatures, antimony levels continually increased over time. As such, PET bottles should not be used for long-term storage.
These findings were further corroborated by research from Kuwait. When stored normally, PET bottles were not of concern, but if stored for longer periods of time or at higher temperatures, antimony levels in water could breach safety limits (Allafi 2020). And beyond the release of antimony into the bottle’s contents, there are other concerns. A study looking at the total release of antimony from PET plastics over their lifecycle concluded that antimony release into the environment is also of concern and should be taken seriously (Chu 2020).
Other factors that can cause concerning levels of antimony to be released into the contents of a PET bottle include sunlight exposure. A study out of Nigeria exposed soft-drink-containing PET bottles to normal room temperature and sunlight for 15 weeks (Umeocho 2024). All but one sample exposed to sunlight exceeded safe levels of antimony.
Another recent study that stored PET bottles for up to one year in temperatures up to 40°C (104°F) found that levels of antimony and plasticizers were under safety limits (Isci 2024).
Conclusion
When stored under more ideal conditions, PET bottles do not appear to pose safety risks due to the migration of antimony into the beverages they contain. However, it is likely that a small but significant percentage of bottles are not stored properly and may contain concerning levels of antimony. PET bottles should not be stored in hot environments (for example, inside of cars in the summertime) and should not be exposed to direct sunlight. Older bottles that are past their expiration should also not be used. Additionally, PET bottles should never be reused due to increased risks for leaching antimony over time.
Hopefully, other polymerization agents beyond antimony could be utilized in the future to fully eliminate the health and environmental risks due to its presence in PET-based plastics. For now, PET bottles should be approached with care to minimize risks with their use.
