Table 1.

Association of PM_2.5 exposure with the peak bilirubin levels on the basis of an increase of 1.0 μg per m³ (95 % CI) in exposure to PM_2.5

Exposure intervals (μg per m3)	Risk in peak bilirubin levels (mg per dL)	Confidence lower limit (mg per dL)	Confidence upper limit (mg per dL)	P value
(0, 10)	0.848	−0.574	2.269	0.157
(10, 35)	0.076	0.027	0.125	0.003
(35,75)	0.029	0.014	0.044	0.031
(75, 200)	0.009	0.002	0.016	0.008
>200	0.01	−0.008	0.028	0.435

For PM_2.5 concentrations ∈ [10, 35] μg per m³, a 1.0 μg per m³ increase in PM_2.5 concentrations was associated with a 0.076 mg per dL (95% CI: 0.027–0.125) rise in the peak bilirubin level. For a 1.0 μg per m³ increase in PM_2.5 concentration, the peak bilirubin level increased by 0.029 mg per dL (95% CI: 0.014–0.044) for PM_2.5 concentrations ∈ (35, 75] μg per m³, and by 0.009 mg per dL (95% CI: 0.002–0.016) for PM_2.5 concentrations ∈ (75, 200] μg per m³. The relationship between PM_2.5 concentrations and the neonatal jaundice risk nearly plateaued at concentrations exceeding 200 μg per m³, such that an additional increase in pollution concentration was not statistically significantly associated with a further increase in bilirubin level