Table 1. Three Primary Components, Units of Analyses, and Modeling Approaches in This Study.

analysis	unit of analysis	outcome variables	primary independent variables	primary modeling approach	sample size
(1) association between PFAS sources (number or total existing effluent from wastewater treatment plants) and PFAS concentrations in 8-digit hydrologic unit codes (watersheds)	watershed of CWS included in recent statewide sampling	PFAS concentrations (natural log transformed)	PFAS sources	log-linear spatial error regression models	476
(2) association between sociodemographic factors and the presence of PFAS sources in watersheds of CWS	CWS included in recent statewide sampling	PFAS contamination sources (binary indicators)	county-level sociodemographic factors	logistic regression models with clustered standard errors (clustered at the county level)	7873
(3) association between sociodemographic factors and PFAS detections (>5 ng/L) or concentrations above lowest state-level MCL in CWS	CWS included in recent statewide sampling	PFAS concentrations above a threshold (>5 ng/L or the lowest state-level MCL; binary indicators)	county-level sociodemographic factors	partially and fully adjusted logistic regression models with clustered standard errors (clustered at the county level)	7873