A recent study examined blood samples that were taken from California women at different time periods -- the 1960s, the 1980s, and 2009. They were examined for the presence of 12 perfluorinated compounds (PFCs).
In each time period, perfluorooctane sulfonate (PFOS) was present at the highest concentration, followed by perfluorooctanoic acid (PFOA).
According to the study, as reported by Green Med Info:
“We found the highest levels of PFOS ... and perfluorohexane sulfonate ... in the 1960s samples, possibly reflecting widespread use of precursor PFCs ... For PFOA, there was an approximately 10-fold increase in median concentrations from the 1960s ... to the1980s ... and a slight drop in the 2009 samples ... For longer chain perfluorocarboxylic acids (PFCAs), there was a continuous build-up in serum from the 1960s to 2009.”