The Consensus: It Is Safe to Reuse Plastic Water Bottles

Can leaching chemicals from the plastic give you cancer?

Many online articles claim that reusing water bottles can lead to cancer due to certain chemicals being released from the plastic.

One chemical that many people are concerned about is BPA, bisphenol A. BPA may disrupt the endocrine system, potentially causing issues related to reproduction and metabolism. BPA is not used to make PET bottles, but can be found in other, more rigid plastics like polycarbonate. Despite this, one study has found very low concentrations (5 ng/L) of BPA in PET-bottled water. Two other studies did not find this chemical, so this finding is inconclusive.

A different chemical, antimony, is used as a catalyst for PET production. Antimony is not considered a carcinogen when ingested but can cause vomiting and diarrhoea. A 2008 study tested the levels of leached antimony in commercially available bottled waters. They did find that leaching occurred gradually overtime, but the amounts were much lower than what is considered dangerous. The concentration at which antimony becomes dangerous is around 6 ppb (parts per billion). The study found that antimony concentrations started at 0.195 ppb and rose to 0.226 ppb after 3 months at 22C.

Antimony is not the only chemical that has been studied in bottled water, a whole range of chemicals from plasticizers to metals have been researched. These studies have found that there are some chemicals, like antimony, that leach into bottled water. As of yet, there is no evidence that these pose a risk to human health.

Is leaving your water bottle in the sun safe?

There are some concerns that the chemical leaching described above happens more frequently at higher temperatures, meaning that leaving your water bottle in the car on a hot day could be dangerous.

The 2008 study on antimony levels did indeed find increased leaching at higher temperatures. When water bottles were left at 60C it took them 176 days to rise above the threshold of 6 ppb, whilst at 80C this only took 1.3 days. These temperatures are very high, so this is likely to only be a problem if you live in a very hot place and regularly leave your water bottle in the sun to heat up.

What about microplastics?

Microplastics are small pieces of plastic. They are found almost everywhere, including in our drinking water. In fact, a study found that 93% of freshly opened plastic water bottles contained some microplastic contamination. The WHO looked into the potential dangers of microplastics, but based on current data they have concluded that they do not pose a significant threat to human health.

Interestingly, Dr Abdulmutalib from the University of Surrey says “Newly released plastic bottles might contain more microplastics compared to the used ones”. Dr Cuhra also thinks that “drinking water out of a used and washed bottle should be safer than a brand-new bottle”. His group found that water fleas grew and reproduced better in plastic tubes that had been washed with warm water than in new plastic containers.

Are there any other risks?

There is one widely-accepted risk of reusing a disposable plastic water bottle, but this is not chemicals – it’s contamination.

As these bottles are not made for durability, they can get easily damaged and crack. Dr Bartolotta says “The plastic used to make bottles is very thin and consequently subject to cracking due to a weaker structure. These cracks can harbour bacteria”. Contamination is particularly likely if the inside of the bottle is damp. Bacteria can grow very fast in bottled water, one study found an increase from 1 colony per ml to 38,000 colonies per ml in 48 hours when the bottle was kept at 37C.

The takeaway:

Of the 8 experts, 6 answered that it is likely that it is safe to reuse plastic water bottles.

Studies of chemical leaching and microplastics have found that these occur at very low levels and are unlikely to pose serious health threats, unless bottles are repeatedly exposed to very high temperatures.

The more likely risk is that of contamination, so if you do reuse a water bottle – remember to wash it regularly.