The pollution of the environment with industrial chemicals is strictly monitored, but the monitoring currently only covers substances that are already known. Researchers have now developed a detection method that can also detect previously unidentifiable fluorinated hydrocarbons. Initial testing of river water samples using this method revealed numerous previously unrecognized industrial chemicals. This is just the tip of the iceberg of polluting chemicals, the team said.
Per- and polyfluorinated chemicals, PFAS for short, have been used in numerous everyday products such as textiles, cookware, packaging, cosmetics and pharmaceuticals since the 1940s. They are not only extremely stable, but also water, grease and dirt-repellent. They owe their stability to their numerous carbon-fluorine bonds, which are among the strongest and most stable single bonds in organic chemistry.
But where the stability of PFAS is an advantage in industrial processing, it becomes a burden on the environment and for us humans. During the manufacture, further processing, application and disposal of the products, these fluorinated hydrocarbons are released into the environment, transported to remote regions and accumulate in organisms or the food chain. There, these chemicals break down very slowly—even in the human body, some have a half-life of nine years. However, some PFAS are suspected of increasing the risk of cancer and reducing the effectiveness of vaccinations.
Chemical Dark Matter
In order to keep an eye on these questionable substances, the environmental impact of the PFAS is regularly monitored. For a long time, however, the classical analytical methods could only be used in the laboratory to examine substances whose identity was known and for which reference substances were available. However, since the industry rarely discloses its ingredients, researchers were usually faced with the problem that they did not know which new PFAS are now in circulation. This is where a new method by Hanna Joerss from the Helmholtz Center Hereon for Environmental Chemistry of Coastal Areas and her colleagues comes in.
“Until recently, we had to know in advance which substances we wanted to detect,” says Joerss. “We have now used a new method that also shows the so-called ‘dark matter’, i.e. the unknown substances in the samples.” To do this, they first took water samples from German and Chinese rivers near industrial sites. With the help of high-resolution mass spectrometry, among other things, they were finally able to identify and quantify all the chemical compounds in the samples by determining the mass.
Banned compounds and questionable substitutes
The results revealed a surprising number of carbon-fluorine compounds: “We identified 86 PFAS – only about 30 of them are routinely analyzed by specialized laboratories, eight we have detected in the environment for the first time,” explains Joerss. “Our method clearly shows that the burden on people and the environment is underestimated – so far we have only seen the tip of the iceberg”. The researchers were able to detect most fluorinated hydrocarbons in the Xiaoqing River with 63 PFAS and in the Bavarian Alz River with 56 PFAS. They even found the chemical perfluorooctanoic acid (PFOA), which has since been banned worldwide, in the Chinese river.
“Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are now banned worldwide, but the industry largely uses substitutes. However, these are often just as problematic for people and the environment – we are talking about regrettable substitutes,” says Joerss, explaining the cat-and-mouse game between industry, science and regulation. “Industry uses new substances whose harmful effects have to be scientifically proven, then it takes years to decades until the substances are regulated,” says Joess. Substitutes such as hexafluoropropylene oxide dimer acid (HFPO-DA), which have not yet been banned, were dominant in the Alz water samples, but they are potentially just as harmful as the conventional compounds.
Source: Helmholtz Center Hereon, Article: Environmental Science & Technology, doi: 10.1021/acs.est.1c07987