A study published last week by the Food Additives & Contaminants: Part A journal — a journal that publishes on natural and man-made food additives and contaminants in food and the animal feed chain and is an affiliated journal of the International Society for Mycotoxicology — might make people think twice when selecting straws for their drinks.
The study — titled “Assessment of poly- and perfluoroalkyl substances (PFAS) in commercially available drinking straws using targeted and suspect screening approaches,” — makes some interesting findings on various undisclosed brands of drinking straws, most notably that many of them contain PFAS.
To conduct their study, the authors subjected 20 paper straws, five glass straws, five bamboo straws, five stainless steel straws, and four plastic straws (39 brands in total found in the Belgian market) to an extensive analysis for 29 different PFAS. The authors found that PFAS were detected in almost all paper-based straws, with highly variable concentrations between brands. PFOA was the most frequently detected component.
In the other types of straws, more often all PFAS were below the Limits of Quantification (LOQ). In bamboo straws, PFAS were detected in the range < LOQ to 3.47 ng/g in four out of five brands.
In glass straws two brands showed concentrations above the LOQ, ranging from < LOQ to 6.65 ng/g, while the concentrations for the other brands were found to be below the LOQ. In the stainless-steel straws, no PFAS concentrations above the LOQ were observed in any of the brands.
Finally, three out of four plastic straw brands contained quantifiable PFAS concentrations, ranging from < LOQ to 0.924 ng/g.
The authors found it noteworthy that “almost all plant-based straws contained PFAS,” which was “expected as PFAS are known to be used to confer stain and water repellency to FCMs (citations omitted).” The authors further explained explanations for why some straws may contain PFAS: “Stainless steel is often made of chromium(III)oxide or other metal oxides and thus has no net charge on the surface of the straws. Therefore, adsorption of pollutants is expected to be limited or even absent in stainless steel.” Further, “some glass straws are made of borosilicate glass so the presence of PFAS in these straws might be due to adsorption to silica minerals (citation omitted).” The authors acknowledged though that they had “no information regarding the type of glass for each of the brands,” so “further examination of how glass can be contaminated with PFAS is required.”
The authors wrote that because certain “ultra-short chained PFAS…are highly water soluble…there is a chance of them migrating from the straw into the drink.”
“Our study confirmed that straws might be an exposure route of TFA and TFMS [types of PFAS found in the straws] which might result in increased exposure to PFAS for humans and subsequent potential toxic effects (citation omitted).”
The authors went on to discuss uncertainty on “which portion of the total PFAS concentration in plant-based food contact materials [FCMs] has intentionally been added to the product (for purposes of e.g. water repellency) and which portion can be considered as background concentration due to recycling procedures.” The latter “could be due to the usage of recycled contaminated paper fibers in the production of new FCMs or to contamination of source materials or the processing water (citations omitted).” The authors traced this contamination to biosolids (fertilizer in agriculture) and “plants grown on contaminated soils can take up PFAS and eventually this pollution can end up in FCMs when these plants are used in the production process (citations omitted).”
However, the authors accept that multiple sources of “potential background contamination makes it difficult to pinpoint an exact source for PFAS in drinking straws.” Given their findings on plant-based and plastic straws and the ongoing issues concerning PFAS, the authors found that “the most sustainable alternative seems to be stainless-steel straws, which can be reused, do not contain PFAS and can be fully recycled.”
And they admit that “more research is needed on PFAS in FCM, the factors affecting the migration of PFAS into food and drinks, and the potential human risks posed by the use of these FCMs.”