Perfluorinated compounds, such as perfluorooctane sulfonate (PFOS), help firefighting foams rapidly flow over flaming liquids such as gasoline and jet fuel, cooling and quenching fires. But despite environmental scientists’ concerns about these possibly toxic compounds accumulating in wildlife and lurking in firefighters’ blood, researchers don’t know the identity of many of the chemicals in the mixtures on the market. For the first time, a new study borrows a medical research tool to pinpoint fluorochemicals in the blood of firefighters, identifying novel compounds that have never before been publicly reported (Environ. Sci. Technol. 2015, DOI: 10.1021/es503653n).
PFOS and other perfluorinated compounds are extremely persistent in the environment, and toxicological studies have linked the chemicals to kidney and bladder cancer and thyroid disease. Airports and military bases use large amounts of firefighting foams for training purposes, and in some cases, the perfluorinated surfactants have slipped into groundwater and surface water supplies, triggering drinking water shutdowns. The complex mix of largely unknown fluorinated compounds in foams included PFOS until 3M, the largest manufacturer of PFOS, voluntarily phased out the compound in 2002 because of toxicity concerns. Firefighting foam manufacturers have since replaced PFOS with shorter chain fluorinated compounds, many of which are not named by manufacturers.
To identify these mystery compounds, earlier studies have taken advantage of improved analytical techniques, such as quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS). “But since QTOF-MS/MS generates thousands of organic compounds from an environmental sample, identifying the unknowns is like trying to find a needle in a haystack,” says María José Gómez Ramos, an analytical chemist at the University of Queensland, in Australia, and an author of the study.
She and her team realized they could isolate the unknowns using a similar strategy to ones that medical researchers use to identify unique biomarkers of diseases. In those studies, researchers might compare compounds found in the blood of cancer patients with those in a healthy control group. For the new study, the scientists compared the fluorinated surfactants in the blood of 20 firefighters with compounds in the blood of 20 students and office workers who had not been exposed to firefighting foams. Gómez Ramos figured that the compounds unique to firefighters would contain unknown fluorinated surfactants.
The scientists ran the blood samples through QTOF-MS/MS, identifying more than 3,000 organic and fluorinated chemicals. But when the research team applied a statistical analysis to the data, a clear separation between the firefighters and controls emerged. The team found nine fluorinated compounds, either exclusively or at significantly higher levels, in the firefighters’ blood. Only five of those compounds appeared in online chemical databases or in the literature. Interpreting the MS data, Gómez Ramos tentatively identified the four unknown compounds as sulfonic acids analogous to PFOS. “It is likely that the unknowns have similar properties to PFOS, such as toxicity and persistence in humans and environment,” Gómez Ramos says. But further studies on the compounds are warranted, she says.
Ian T. Cousins, an environmental chemist at Stockholm University, points out that these new sulfonic acids haven’t been found in commercial foams, so they might be metabolites. But if they are in the foams, “then we should be concerned for highly exposed groups like firefighters,” Cousins says. “We know nothing about their risks.”