Table 2.

Evaluation the impact of pollutants on mammographic breast density with stepwise and non-stepwise logistic regression.

	Non-stepwise algorithm				Stepwise algorithm
	P-value	OR	95C.I Lower	95C.I Upper	P-value	OR	95C.I Lower	95C.I Upper
CO (ppm)	0.024	0.429	0.206	0.893	0.001	0.331	0.172	0.637
NO2 (ppb)	0.055	1.045	0.999	1.093	0.003	1.039	1.013	1.066
O3 (ppb)	0.870	0.988	0.852	1.145
SO2 (ppb)	0.605	0.926	0.692	1.240
PM10 (µg/m3)	0.378	0.944	0.829	1.073
PM2.5 (µg/m3)	0.305	1.129	0.896	1.422
Constant	<0.001	1.754		—	<0.001	1.758	—

OR = Odds ratio, C.I = Confidence interval, NO₂ = Nitrogen dioxide (NO₂), SO₂ = Sulfur dioxide, CO = Carbon monoxide, O₃ = Ozone, PM = Particulate matter.