Systematic Evidence Mapping of Potential Exposure Pathways for Per- and Polyfluoroalkyl Substances Based on Measured Occurrence in Multiple Media

Given that human biomonitoring surveys show per- and
polyfluoroalkyl
substances (PFAS) to be ubiquitous, humans can be exposed to PFAS
through various sources, including drinking water, food, and indoor
environmental media. Data on the nature and level of PFAS in residential
environments are required to identify important pathways for human
exposure. This work investigated important pathways of exposure to
PFAS by reviewing, curating, and mapping evidence for the measured
occurrence of PFAS in exposure media. Real-world occurrence for 20
PFAS was targeted primarily in media commonly related to human exposure
(outdoor and indoor air, indoor dust, drinking water, food, food packaging,
articles, and products, and soil). A systematic-mapping process was
implemented to conduct title-abstract and full-text screening and
to extract PECO-relevant primary data into comprehensive evidence
databases. Parameters of interest included the following: sampling
dates and locations, numbers of collection sites and participants,
detection frequencies, and occurrence statistics. Detailed data were
extracted on PFAS occurrence in indoor and environmental media from
229 references and on PFAS occurrence in human matrices where available
from those references. Studies of PFAS occurrence became numerous
after 2005. Studies were most abundant for PFOA (80% of the references)
and PFOS (77%). Many studies analyzed additional PFAS, particularly,
PFNA and PFHxS (60% of references each). Food (38%) and drinking water
(23%) were the commonly studied media. Most studies found detectable
levels of PFAS, and detectable levels were reported in a majority
of states in the United States. Half or more of the limited studies
for indoor air and products detected PFAS in 50% or more of the collected
samples. The resulting databases can inform problem formulation for
systematic reviews to address specific PFAS exposure queries and questions,
support prioritization of PFAS sampling, and inform PFAS exposure
measurement studies. The search strategy should be extended and implemented
to support living evidence review in this rapidly advancing area.