Table 3.

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

Cumulative Dose (mg·y/m3)	N	Lead Poisoning (N)	Abnormal ZPP (N)
0-	913	68	41
2-	79	22	14
4-	37	13	7
6-	25	6	6
8-	27	9	8
χ2		78.061	64.224
p-value		<0.001	<0.001
Linear trend
χ2		56.319	58.191
p-value		<0.001	<0.001

Note: 60 μg/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.