Have you ever experienced the strange taste of water after it has been in a reusable plastic bottle for a while? It appears to be either a valid and worrisome reason behind. Researchers at the University of Copenhagen have found several hundred different chemical substances in tap water stored in reusable plastic bottles. It is aready known that plasticizers are added to common plastic bottles to allow a proper solidity and handling. Plastic bottles without plasticizers, indeed, are deemed very soft and not suitable to carry large amounts of fluid or water. Several of these substances are indeed potentially harmful to human health. For example, one additive called N-hydroxy-diethylamine is known to be toxic for liver cells and reproduction. There is a need for better regulation and manufacturing standards for manufacturers, according to the chemists behind the study. Chemists have studied which chemical substances are released into liquids by popular types of soft plastic reusable bottles. The results were quite a surprise.
Jan H. Christensen, Professor of Environmental Analytical Chemistry at the University of Copenhagen’s Department of Plant and Environmental Sciences and his team measured these chemicals in tap water after being stored at different timepoints. After barely 24 hours, there was a large amount of chemical inside 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. To be exact, scientists detected more than 400 different substances from the 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 despite of their identity, the toxicity of at least 70 % remains unknown. Photo-initiators are among the toxic substances which worry researchers the most. These are known to behave as endocrine disruptors (EDCs) and/or carcinogens.
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. Three different types of drinking bottles were tested, all of which are found in Danish stores. Two of the bottles are made of biodegradable plastic, according to the manufacturer. Both new and heavily used bottles were used. The bottles were tested both before and after machine washing, and after five extra rinses in tap water. The researchers carried out a so-called non-target screening (NTS) using a liquid chromatograph and a mass spectrometer, where, as with traditional methods, it is not limited to analysing the substances that are suspected to be present, but instead screen for all substances present.The researchers 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. In new reusable bottles, almost 500 different compounds remained in the water after an additional rinse. Over 100 of these substances came from the plastic itself. Furthermore, 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. The researchers suspect that manufacturers add intentionally only a small proportion of the substances found. 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 plasticizers degrades, it is converted into DEET. According to professor Christensen, 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”.
The research now apperas in the Journal of Hazardous Materials.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Tisler S, Christensen JH. J Hazard Mater 2022; 429:128331.
Banaderakhshan R et al. Chemosphere 2022; 286(Pt 3):131842.
Farooq MU et al. Envir Sci Pollut Res Int. 2021; 28(40):57090-98.
Dott. Gianfrancesco Cormaci
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