Researchers at the University of Copenhagen have discovered several hundred different chemical substances in tap water stored in reusable plastic bottles.
Several of these substances are potentially harmful to human health.
I remember the taste. It was while travelling in India and it came from to only so-called ‘safe’ water supply I could find: plastic bottles. Yes, it was probably because the plastic bottle had been a) reused or b) sitting too long in the sun, but.. there was a definite taste that wasn’t .. water.
Now we learn exactly what that taste was!
Chemists from the University of Copenhagen have discovered that a range of chemicals are released into liquids by popular types of soft plastic reusable bottles.
The results were terrifying. I immediately thought about the number of bottles that may have been ‘microdosing’ me for the last 50 years!
"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," says Jan H. Christensen, Professor of Environmental Analytical Chemistry at the University of Copenhagen's Department of Plant and Environmental Sciences.
Endocrine Disruptors and Bug Spray
Professor Christensen and fellow researcher Selina Tisler found more than 400 different substances from bottle plastic – and over 3,500 substances derived from dishwasher soap. A large portion of these are unknown substances that the researchers have yet to identify.
But even of the identified chemicals, the toxicity of at least 70 % remains unknown.
Among the toxic substances in the water are photo-initiators, which worried the researchers. A photoinitiator is a molecule that creates reactive species (free radicals, cations or anions) when exposed to radiation (UV or visible).
(Ian: Like those bottles in India that sat in the sun for.. how long?)
Synthetic photoinitiators are key components in photopolymers (i.e., photo-curable coatings, adhesives and dental restoratives). These are known to have potentially harmful effects on health in organisms, such as being endocrine disruptors and carcinogens.
The researchers found a variety of plastic softeners, antioxidants and release agents used in the manufacture of the plastic, as well as Diethyltoluamide (DEET), commonly known as the active substance in mosquito spray.
Machine washing adds more substances into the bottled water
In their experiments, the researchers mimicked the ways in which many people typically use plastic drinks bottles. People often drink water that has been kept in bottles for several hours.
They left ordinary tap water in both new and used drinking bottles for 24 hours, both before and after machine washing, as well as after the bottles had been in the dishwasher and rinsed thoroughly in tap water.
"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,"
~explained postdoctoral researcher and first author Selina Tisler of the Department of Plant and Environmental Sciences.
In new reusable bottles, close to 500 different substances remained in the water after an additional rinse. Over 100 of these substances came from the plastic itself.
They have yet to conclude whether the water in the bottles is harmful to health, as they currently have only an estimate of the concentrations of the substances and toxicological assessments have 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," says Selina 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 unknowingly add hundreds or thousands of substances to the water ourselves.
Researchers suspect that bottle manufacturers only add a small proportion of the substances found intentionally. The majority have inadvertently occurred either during the production process or during use, where substances may have been converted from other substances. This includes the presence of the mosquito repellent DEET, where the researchers hypothesize that as one of the plastic softeners degrades, it is converted into DEET.
"But even of the known substances that manufacturers deliberately add, only a tiny fraction of the toxicity has been studied. So, as a consumer, you don't know if any of the others have a detrimental effect on your health," says Selina Tisler.
Too little knowledge, too leniently regulated
According to the researchers, the results reflect a lack of both knowledge and regulation:
"The study exemplifies how little knowledge there is about the chemicals emitted from the products that our food and drink come in contact with. And, it is a general problem that measurement regulations during production are very lenient. Fortunately, both in Denmark and internationally, we are looking into how to better regulate this area," says Jan H. Christensen.
In the meantime, Selina Tisler hopes that companies take responsibility on their own accord:
"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," Tisler concludes.
The study results are published in the scientific journal Journal of Hazardous Materials.
Ian: We’ve taken great pains to identify the plastics used in all of our products and to find whether they were FDA approved. And of course, with your own water filter like the UltraStream, you never need to dishwash it!
- Selina Tisler, Jan H. Christensen. Non-target screening for the identification of migrating compounds from reusable plastic bottles into drinking water. Journal of Hazardous Materials, 2022; 429: 128331 DOI: 10.1016/j.jhazmat.2022.128331