Table 3.

Number of significant features associated with air pollutant by negative and positive ion mode.

	Number of features with p-value < 0.05		Number of features with FDRa < 0.1
Air Pollution	Negative mode	Positive mode	Negative mode	Positive mode
1 month NO2	435	191	0	0
1 month O3	599	183	3	0
1 month PM2.5	573	172	3	0
1 month PM10	433	167	0	0
1 year NO2	589	163	0	0
1 year O3	313	96	0	0
1 year PM2.5	398	214	0	0
1 year PM10	291	151	9	1

^aFalse discovery rate (FDR) of raw p-value based on Benjamini-Hochberg adjustment