Concentrations of Perfluorinated Chemicals in Foods

Perfluorochemicals (PFCs) are emerging persistent pollutants. They are widely used in various products because of their stability and unique physicochemical properties. However, their persistence and bioaccumulation have resulted in the spread of these compounds in the environment, organisms and humans. PFCs have caused concerns because they are hepatoxic and are also potentially harmful to the development and reproduction of organisms. Human would expose to PFCs via drinking water, food intake and dust; food ingestion may be the primarily exposure route.
This study measured eight PFCs (perfluorohexanoic acid, PFHxA)、(perfluorooctanoic acid, PFOA)、(perfluorononanoic acid, PFNA)、(perfluorodecanoic acid, PFDA)、(perfluoroundecanoic acid, PFUnDA)、(perfluorododecanoic acid, PFDoDA)、(perfluorohexane sulfonate, PFHxS)and (perfluorooctane sulfonate, PFOS) in 14 different types of foods, which were randomly purchased from two traditional markets in Taipei City, including rice, flour, pork, beef, chicken, salmon (sea fish), Grass carp (freshwater fish), oysters, shrimp, clams, squid, pig liver, chicken eggs, and whole milk. Combining the levels of PFCs in foods we detected and the data from the Council of Agriculture of Taiwan, we evaluated the PFCs exposure from food intake.
Solid samples were homogenized and one-gram wet samples were further homogenized with 10 mL of 0.5 N potassium hydroxide (KOH) in methanol for 2 minutes and then were sonicated for 2 hours. After centrifugation, 5 mL supernatant of the samples were diluted with 500-mL Milli-Q water then were adjusted to pH 3.5 by formic acid. 25-mL whole milk samples were added with six stable isotope-labeled standards and then were mixed with 450 mL 0.5 N potassium hydroxide (KOH) in Milli-Q water for digestion then adjusted to pH 3.5 by formic acid. All samples were filtrated through 90-mm glass filter before undergoing solid-phase extractions.
Digested samples after the dilution were further extracted with Atlantic HLB disk by automated solid-phase extraction. The 20-mL methanol containing 0.1% ammonium hydroxide (v/v) eluents were concentrated by a SpeedVac concentrator and finally were analyzed by ultra-high performance liquid chromatography/tandem mass spectrometry at negative electrospray ionization.
Five PFCs (PFHxA、PFOA、PFDA、PFUnDA、PFDoDA) can be detected in most samples. Two types of cereal samples, rice and flour, with geometric means of PFCs ranged from 0.04 to 8.90 ng/g and 0.02 to 8.84 ng/g, respectively, contained relatively lower concentrations of PFCs than those in meat and sea food samples, with the geometric means ranged from 0.08 to 12.1 ng/g and from 0.04 to 12.3 ng/g, respectively). The concentrations of PFCs were often higher in sea food than in meat samples. The highest concentrations were found in pork liver (the geometric mean of the total eight PFC concentrations were 52.8 ng/g.)
PFOA (geometric mean 1.44-12.1 ng/g), PFDA (geometric mean 0.84-20.9 ng/g), and PFDoDA (geometric mean 1.19-15.1 ng/g) were the most commonly detected compounds and the levels were mostly higher than others. PFUnDA (geometric mean 0.06-2.10 ng/g) and PFHxA (geometric mean 0.03-1.33 ng/g) were also detected frequently. However, PFNA、PFHxS and PFOS were not detected in most food samples. The higher concentrations of PFOA were than others would relate to the continuous use of the precursors in several products. Furthermore, PFCs with longer alkyl chains were often found in higher levels in most samples.
In this study, we detected eight PFCs in different types of foods, and provide invaluable information on the concentrations of PFCs in foods, which are essential for the exposure of PFCs from diet.