Table 4.

Correlation between cumulative lead fumes exposure and lead poisoning and ZPP.

Cumulative Dose (mg·y/m3)	N	Lead Poisoning (N)	Abnormal ZPP (N)
0-	441	114	83
1-	148	56	37
2-	47	28	17
3-	28	10	10
χ2		26.748	7.024
p-value		<0.001	>0.05
Linear trend
χ2		17.249	5.284
p-value		<0.001	<0.05

Note: 60 mg/dL blood lead, 120 mg/L urinary lead and 0.291 mmol/dL ZPP are diagnostic values for lead poisoning in China and results equal or greater than these values were judged to be abnormal.