Table 4.

Effect of high groundwater use^a, race, and soil zinc^b levels on PrCA incidence^c in SC, 1996–2002

Variables			RRd	95% CIe
High groundwater use	Low % AA (< 36%)	High zinc (≥13.4 ppm; n = 13)	Referent	–
	Low % AA (< 36%)	Low zinc (< 13.4 ppm; n = 72)	1.007	0.875, 1.157
High groundwater use	High % AA (≥64%)	High zinc (≥13.4 ppm; n = 16)	Referent	–
	High % AA (≥64%)	Low zinc (< 13.4 ppm; n = 71)	0.974	0.843, 1.127

^aCensus tracts with ≥50% groundwater consumption

^bMedian value (ppm) split within racial categories

^cAdjusted for median household income

^dRate ratio

^eConfidence interval