Table 2.

Mean and mean differences in FEV₁, FVC, and FEV₁/FVC (%) by quartile of blood lead and cadmium levels, adjusted age, sex, BMI, and smoking status^*

Variable	n	FEV1(L)		P-value	FVC (L)		P-value	FEV1/FVC (%)		P-value
		Mean (SE)	Mean difference (SE)		Mean (SE)	Mean difference (SE)		Mean (SE)	Mean difference (SE)
Blood lead level, μg/dL**
≤1.85	1,486	2.85 (0.01)	Ref		3.61 (0.02)	Ref		79.0 (0.2)	Ref
1.86–2.43	1,480	2.90 (0.01)	0.05 (0.02)	0.002	3.68 (0.01)	0.07 (0.02)	0.001	78.9 (0.2)	−0.1 (0.3)	0.753
2.44–3.16	1,477	2.91 (0.01)	0.06 (0.02)	0.001	3.68 (0.01)	0.07 (0.02)	0.001	79.1 (0.2)	0.1 (0.3)	0.771
≥3.17	1,472	2.89 (0.01)	0.04 (0.02)	0.039	3.69 (0.02)	0.08 (0.02)	0.001	78.4 (0.2)	−0.6 (0.3)	0.025
P-value for Wald F statistic			0.004			0.001			0.013
Blood cadmium level, μg/dL**
≤0.77	1,455	2.88 (0.01)	Ref		3.63 (0.02)	Ref		79.2 (0.2)	Ref
0.78–1.11	1,510	2.89 (0.01)	0.01 (0.02)	0.498	3.67 (0.01)	0.04 (0.02)	0.047	78.9 (0.2)	−0.3 (0.3)	0.211
1.12–1.56	1,455	2.90 (0.01)	0.03 (0.02)	0.179	3.69 (0.01)	0.06 (0.02)	0.005	78.9 (0.2)	−0.4 (0.3)	0.152
≥1.57	1,495	2.88 (0.01)	0 (0.02)	0.993	3.68 (0.01)	0.05 (0.02)	0.008	78.3 (0.2)	−1.0 (0.3)	<0.001
P-value for Wald F statistic				0.432			0.024			0.004

Notes

^*Data are presented as the adjusted mean (SE) and mean difference (SE) unless otherwise indicated;

^**subjects were categorized into four groups according to blood lead and cadmium level as the 25th percentile, the 50th percentile, the 75th percentile, and the 100th percentile.

Abbreviations: BMI, body mass index; SE, standard error; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; Ref, reference.