PM2.5 constituent exposures and maternal circulatory homocysteine in early pregnancy

Table 4 Thirteen − week (3 − month) cumulative associations of an IQR increase in PM_2.5 and constituent exposures with percentage changes in serum Hcy in all participants, EPL group, and NEP group

Parameter	All participants (n = 324)		EPL (n = 162)		NEP (n = 162)
Parameter	β (95% CI)	p-value	β (95% CI)	p-value	β (95% CI)	p-value
Pollutant concentration
PM_2.5	66.0 (34.6, 104.8)	< 0.001	62.9 (16.9, 126.9)	0.005	70.9 (28.7, 127.0)	< 0.001
BC	65.4 (38.7, 97.1)	< 0.001	79.9 (37.8, 134.8)	< 0.001	52.7 (19.8, 94.7)	< 0.001
OM	67.5 (38.4, 102.6)	< 0.001	78.1 (33.2, 138.1)	< 0.001	60.3 (22.7, 109.5)	< 0.001
NO₃^–	73.7 (44.6, 108.5)	< 0.001	80.9 (35.2, 142.1)	< 0.001	71.9 (35.0, 118.7)	< 0.001
NH₄⁺	64.9 (40.1, 94.1)	< 0.001	71.8 (32.7, 122.4)	< 0.001	62.9 (31.3, 102.2)	< 0.001
SO₄^2–	34.5 (22.7, 47.5)	< 0.001	40.4 (21.5, 62.1)	< 0.001	29.9 (14.2, 47.7)	< 0.001
Constituent residual
BC	7.5 (1.8, 13.5)	0.011	12.0 (2.9, 21.9)	0.010	1.2 (-6.2, 9.3)	0.754
OM	5.5 (0.04, 11.3)	0.051	9.5 (0.8, 18.9)	0.033	1.0 (-6.3, 8.8)	0.801
NO₃^–	4.4 (-1.8, 11.0)	0.167	5.5 (-4.2, 16.1)	0.277	2.9 (-5.1, 11.5)	0.494
NH₄⁺	4.6 (-1.7, 11.3)	0.157	5.9 (-4.0, 16.7)	0.255	2.7 (-5.4, 11.6)	0.525
SO₄^2–	15.1 (8.1, 22.5)	< 0.001	21.1 (9.7, 33.8)	< 0.001	9.6 (0.5, 19.6)	0.040

Note: The independent variables simultaneously included three cross–basis functions generated by lag 1–13 weeks before serum collection and weekly exposure to pollutant (concentration of PM_2.5 or each constituent, or residual of each constituent), temperature, and relative humidity, respectively, Ln5-MeTHF, all demographic characteristics presented in Table 1, and group (EPL or NEP). The IQRs of concentration of PM_2.5, BC, OM, NO₃^–, NH₄⁺, and SO₄^2– in the analyses were 29, 1.1, 5.8, 6.7, 3.6, and 2.5 µg/m³, respectively. The IQRs of residual of BC, OM, NO₃^–, NH₄⁺, and SO₄^2– in the analyses were 0.2, 0.9, 1.5, 0.9, and 1.1, respectively

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