What are children’s waterproof clothes made of?
It is chic today to wear sporty clothes even in the city and these are often waterproof or water repellent. These kinds of materials have made life simpler, but what is it that makes them water repellent? Most often it is a polymer, i.e. some kind of plastic material, containing fluoride in an organic structure meaning that it attached to a carbon or hydrocarbon chain. Many well known trade marks such as “gore-tex” or “teflon” materials which are widely used in outdoor clothing or shoes, have this kind of coating. However, as we have seen several times in this book, persistence is a double-edged sword. It requires that some precautions need to be taken when disposing of these products even if their use, as such, is completely safe.
Perfluorinated alkylated substances (PFAS) such as perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid and its salts perfluorooctanesulfonates (PFOS) are widely used compounds which are found in many consumer products. They have been used in textile industries, metal engineering, fire-fighting foams, photography, semiconductor industries, and aeroplane industries. One end of the PFOA and PFOS molecules is water soluble, and the other end is water repellent. This is the basis for their use as surfactants, in simple terms this means that they mix with both water and fats – in that respect they are similar to soaps. PFOA is also an important starting material for polymer production (see below).
These materials are very stable and poorly biodegradable and therefore they are also capable of bioaccumulating. In fact, they have been found in biota in all parts of the world. The most important toxic effects are foetal toxicity (mortality) and liver damage. The elimination half life of PFOA has been reported to be around 4 years.
The largest manufacturer of PFOA announced in the year 2000 that they intended to discontinue the production because of its bioaccumulation in food chains. However, other manufacturers continue to use these materials and related substances. They have been widely used in textile, leather and fur products, paper products, shampoos, toothpastes, cosmetics, rinsing liquids of dishwashers, car washes, oven cleaners, and polishing waxes.
Due to their ubiquitous nature, human exposures are quite likely, and PFOA compounds have been detected in drinking water both in the U.S. and in Germany. They have also been analysed in fish swimming in contaminated waters. In the American population, one of the major sources of exposure seems to be microwave popcorn bags. In the Nordic countries, some of the highest concentrations were found in bottom filtrates of waste dumpsites. The adverse effects in humans are uncertain but there is some evidence for carcinogenicity emerging from animal studies.
There is a trend to phase out other uses of PFOA and to allow its use only as an intermediate in the production of polytetrafluoroethylene.
Polytetrafluoroethylene, commonly known as “Teflon®”, is an important fluorine containing polymer used in many consumer products including non-stick coating for pots and pans. Teflon is so slippery that it is the only known surface to which a gecko lizard cannot stick. Its problem is its disintegration to small very harmful particles if overheated (over 350°C). They cause acute lung damage probably because of the active radicals present in the particles. Therefore one should be very careful with teflon kitchenware and not overheat or burn these pans or leave these pots unattended on a hot plate.
A special kind of porous and fibrillary polytetrafluoroethylene is used in “Gore-tex®” textiles. These are water repellent but allow moisture to penetrate as vapour better than some other synthetic materials. However, these clothes can produce a toxic smoke if they are burned.
Another use of polytetrafluoroethylene is in ski waxes. In this case, the molecules in those products are smaller than those in kitchenware, and they may evaporate in the elevated temperatures used in waxing so that some people waxing their skis have experienced breathing difficulties. Waxing with ski waxes containing fluorinated hydrocarbons must be performed outdoors or at least by using a ventilated hood.
The intention of developing durable and technically excellent products often seems to lead to the creation of substances which are also persistent in nature, causing them to accumulate in the environment over the years.
One level up: A favourite of children - and some adults too
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