PET bottles are often carried in summer temperatures as they are easier to transport due to their low weight and are more shatterproof than glass bottles. They are particularly advantageous for people for whom glass bottles would be far too heavy to carry, such as small children or athletes. However, exposure to sunlight can be a problem with these PET bottles filled with water. Sunlight can cause volatile organic compounds (VOCs) to be released inside the plastic bottles, which can be harmful to health.
Definition of PET
PET is the abbreviation for polyethylene terephthalate. The thermoplastic polyethylene terephthalate (abbreviation PET) is mainly used for food containers such as PET bottles or for medical and laboratory products. As polyethylene terephthalate is also resistant to numerous chemicals, it is also used in the production of textiles and films.
PET bottles can often be recognized by the fact that they are labelled with the abbreviation PET or the triangle-shaped symbol consisting of arrows with the code number 1 symbol.
Effect of sunlight on PET bottles
Harmful chemical compounds are released more easily when exposed to sunlight. They are released from the plastic and can enter the environment, i.e. the water or ambient air.
The volatile organic compounds that are released into the air inside plastic bottles and the possible effects they can have on human health have only recently been researched in more detail.
Study on PET bottles
The team of researchers led by Ruijuan Liu from the Guangdong Key Laboratory of Environmental Pollution and Health at Jinan University has systematically investigated which volatile organic compounds (VOCs) can be released from plastic containers into the air inside the bottle. The results of their research were published in the journal “Eco-Environment & Health” in 2024.
Effect of the sun and UV-A light on PET bottles
In order to find out to what extent PET bottles react with water under sunlight, in the dark or under artificial UV-A light, Ruijuan Liu and his team conducted experiments with water bottles made of PET (polyethylene terephthalate).
In these experiments, six different types of PET plastic bottles were stored with natural sunlight, irradiated with UV-A light or without exposure to light.
In this study, the PET bottles to be examined were either empty or only half-filled with still water or sparkling water. They stood in the sun on warm summer days or at room temperature under a lamp with UV-A radiation or in the dark.
The samples obtained were then analyzed using a spectrometer to determine whether organic substances could have been released under the different radiation conditions. Depending on the type of bottle and the light source, the substances that had collected inside the bottle varied.
Study result – volatile organic substances found in PET bottles
The researchers found six to 46 chemicals in the plastic bottles made of polyethylene terephthalate after seven days of exposure to sunlight. Most of these substances formed in the bottles after just one day of exposure to sunlight. In the other PET water bottles, 19 and 37 chemicals were detected after UV-A irradiation.
In general, the concentration of toxic substances in the plastic containers increased with the time of irradiation. This was higher for still water than for sparkling water. However, it only reached a maximum of a few nanograms per bottle. In the water stored in the plastic bottles in the dark, they found either no volatile chemicals or only small amounts.
All PET water bottles tested that were exposed to sunlight or UV-A radiation released volatile organic compounds (VOCs).
Different VOC substances depending on the bottle type
Various volatile organic compounds were released in the PET bottles examined. These included alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids and aromatics. The composition and concentration of these substances varied depending on the type of bottle.
The researchers attributed these differences to possible light-induced ageing and the degradation of the polyethylene terephthalate structure in the water containers. In addition, they also identified highly toxic volatile organic compounds such as the carcinogenic substances n-hexadecane and methylbenzene. In addition, there are also substances that can irritate the respiratory tract.
Conclusions from the study results
After completing their studies, Liu and her colleagues assume that more and more VOCs accumulate in a storage location over time and with continuous exposure to light. This also increases the risk of inhaling larger quantities.
In addition, these substances can dissolve in water and then have consequences for health under certain circumstances. However, according to the researchers, the concentration of chemicals released from a single PET bottle was not sufficient to be harmful to health when inhaled while drinking.
According to the researchers, the volatile substances detected could probably have entered the PET during the manufacture of the bottles or during filling. They could possibly come from residues of lubricants and solvents, fragrances from other foods or plasticizers. They could also be from the PET itself.
Avoid health risks
The research team led by Ruijuan Liu recommends that consumers should be made aware of the risks posed by the release of possible volatile organic compounds from PET bottles. This particularly applies to plastic bottles containing drinking water that are exposed to sunlight for long periods of time. The researchers therefore recommend storing these bottles in the dark. Particularly in summer, these plastic bottles should be stored in the shade, as chemicals can be released from the plastic in the heat.
Manufacturers and distributors should pay more attention to the possible dangers of potentially harmful substances from PET bottles and also make the distribution channels safer. PET bottles should be produced and stored in such a way that they can release fewer potentially harmful VOCs.
Alternative to PET bottles
Glass bottles are the best alternative to PET bottles. Even if they weigh around 25 times more than the lighter plastic bottles. Unlike PET bottles, glass containers do not release any harmful substances or interact with other substances. While liquids from PET bottles can often taste of dissolved plastic, glass bottles retain the original taste of water as they are odorless and tasteless. From a health point of view, glass containers are the safest material for food.
Sources:
Image source: 123rf.com © naumoid, image no. 32053699
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