Table 1.

Summary and synthesis of epidemiologic and experimental evidence. (Complete study details results can be found in Supplemental Tables S8 and S9).

Combination	Epidemiologic evidence	Experimental evidence	Overall
PM and O3	Little evidence for joint effects	Synergistic, antagonistic, and no overall interactive effects detected across studies	Results inconsistent within disciplines
	Modest evidence for effect modification (larger effects for PM10 when O3 was higher)	Limited support for ability of O3 to modify effect of PM	No coherence across scientific disciplines, CVD health effects, or time periods of exposure
	(Bobb et al. 2013; Kalantzi et al., 2011; Crouse et al. 2015; Jerrett et al. 2013; Weichenthal et al., 2014; Hong et al., 2002; Wong et al., 1999)	(Brook et al., 2009; Urch et al., 2010; Fakhri et al., 2009; Sivagangabalan et al., 2011; Kusha et al. 2012; Farraj et al., 2015; Kurhanewicz et al. 2014a; Kurhanewicz et al. 2014b; Wagner et al., 2014; Tankersley et al., 2013; Kodavanti et al., 2011)
PM and NO2	Long-term NO2 exposure may modify short-term PM2.5 exposure (larger effects for short-term exposure to PM2.5 when long-term concentrations of NO2 are higher)	Evidence for both synergistic and antagonistic effects depending on CVD endpoint for controlled human exposure study (Huang et al., 2012)	Results inconsistent within disciplines
	(Bobb et al. 2013; Weichenthal et al., 2014; Wong et al., 1999; Yu et al., 2013; Hong et al., 2002; Crouse et al. 2015; Jerrett et al. 2013)		Modest evidence of multipollutant effects
O3 and NO2	No evidence of joint effects and inconsistent results for effect measure modification across CVD endpoints	1 study provided limited evidence of synergism (Dreschler-Parks et al., 1995)	Results inconsistent within disciplines
	(Weichenthal et al., 2014; Wong et al., 1999; Ponka et al., 1998; Crouse et al. 2015; Jerrett et al. 2013; Kalantzi et al., 2011)		Modest evidence of multipollutant effects
PM and CO	No evidence of joint effects or effect measure modification among 3 studies (Dennekamp et al., 2015; Hong et al., 2002; Kalantzi et al., 2011)	Among 2 studies, evidence for interaction from 1 (Wellenius et al., 2004, 2006)	Limited evidence of multipollutant effects
O3 and CO	No evidence of joint effects or effect measure modification among 2 studies (Samoli et al., 2007; Kalantzi et al., 2011)	No studies	No evidence of multipollutant effects
Mixtures	Index studies observed consistent evidence between indices and CVD endpoints (Fink et al. 2012; Peters et al., 1997, 1999; 2001; Chen et al., 2014; Briet et al., 2007; Li et al., 2015; Poursafa et al., 2016; Johannesson et al. 2014; Baja et al., 2012, 2013)	No studies	Unclear how to use these studies to inform questions about multipollutant exposures
	Cluster studies observed consistent evidence between clusters and CVD endpoints (Park et al., 2007; Grass and Cane, 2008; Mar et al., 2000)
	Whole atmosphere studies inconsistently associated with CVD effects (Kubesch et al., 2014; Laumbach et al., 2010; Peel et al., 2010; Davoodi et al., 2010)