Hundreds of different chemicals found in tap water kept in plastic bottles for long periods, including some potentially dangerous to human health, according to a study published in the Journal of Hazardous Materials (1). The authors argue that there is a need for better regulation and manufacturing standards to protect the public.
Have you’ve ever noticed how water tastes bad after it has been stored in a plastic bottle for a while? To understand why two chemists from the University of Copenhagen tested the water for the presence of different chemical substances in popular types of soft plastic reusable bottles.
The results were shocking. “We were taken aback by the large amount of chemical substances we found in water after 24 hours in the bottles. There were hundreds of substances in the water – including substances never before found in plastic, as well as substances that are potentially harmful to health. After a dishwasher cycle, there were several thousand,” said Jan Christensen, Professor of Environmental Analytical Chemistry at the University of Copenhagen’s Department of Plant and Environmental Sciences.
Prof Christensen and colleague Selina Tisler found more than 400 different chemicals derived from plastic and over 3500 chemicals from dishwasher soap. The list includes several plastic softeners, antioxidants, carcinogens, and many others. Worryingly, researchers can only identify a fraction of these chemicals and don’t know whether any of them are toxic or not.
The idea behind this study was to mimic the way people normally use plastic bottles. It’s common for water to stay in the plastic bottles for several hours. The team left tap water in both new and used bottles for 24 hours. The test also included bottles washed in a washing machine and used straight away and bottles washed in a washing machine and rinsed thoroughly before use.
“What is released most after machine washing are the soap substances from the surface. Most of the chemicals that come from the water bottle itself remain after machine washing and extra rinsing. The most toxic substances that we identified actually came after the bottle had been in the dishwasher – presumably because washing wears down the plastic and thereby increases leaching,” said first author Selina Tisler of the Department of Plant and Environmental Sciences.
The researchers found close to 500 chemicals in the bottles even after the additional rinse after washing, with over 100 of these being from the plastic itself. Work is still undergoing to determine if the water is harmful to our health, with toxicological assessments yet to be completed. “Just because these substances are in the water doesn’t mean that the water is toxic and affects us, humans. But the problem is, is that we just don’t know. And in principle, it isn’t all that great to be drinking soap residues or other chemicals,” said Tisler.
“We care so much about low levels of pesticides in our drinking water. But when we pour water into a container to drink from, we unflinchingly add hundreds or thousands of substances to the water ourselves. Although we cannot yet say whether the substances in the reusable bottles affect our health, I’ll be using a glass or quality stainless steel bottle in the future,” added Christensen.
The authors believe that most of the chemicals are present in the plastic inadvertently, either occurring during production or during use, with new chemicals appearing after being converted from other substances. This includes the mosquito repellent DEET, which the team speculated may result from the degradation of a plastic softener.
According to the team, this occurs due to a lack of regulation in this field, and they urge companies to take responsibility. “Hopefully, companies that put their names on reusable plastic bottles will be more careful about the products they purchase from suppliers and perhaps place greater demands on suppliers to investigate the substances found in what they manufacture,” concluded Tisler.
(1) S and Christensen J (2022) Non-target screening for the identification of migrating compounds from reusable plastic bottles into drinking water. Journal of Hazardous Materials, https://doi.org/10.1016/j.jhazmat.2022.128331.