Table 3.

Associations between wastewater impacted public drinking water in homogenous supplies and breast cancer.

	Cases	Controls	Adjusted OR (95% CI)a	Adjusted OR (95% CI)b
Average annual excess nitrate-N concentration (mg/L)
0 to < .3	280	250	1.0 (referent)	1.0 (referent)
.3 to < .6	163	141	1.0 (0.7 – 1.3)	1.0 (0.7 – 1.3)
.6 to < .9	149	144	0.9 (0.6 – 1.2)	0.9 (0.6 – 1.2)
.9 to < 1.2	78	79	0.8 (0.5 – 1.2)	0.8 (0.5 – 1.2)
≥ 1.2	12	9	1.2 (0.5 – 2.9)	1.2 (0.5 – 3.1)
Sum of annual excess nitrate-N concentrations (mg/L)
0 to < .01	18	17	0.8 (0.4 – 1.6)	0.9 (0.4 – 1.9)
.01 to < .1	43	41	0.9 (0.5 – 1.4)	1.0 (0.6 – 1.7)
.1 to < 1	104	104	0.9 (0.6 – 1.2)	1.1 (0.8 – 1.5)
1 to < 10	390	344	1.0 (referent)	1.0 (referent)
≥ 10	127	117	1.0 (0.7 – 1.3)	0.9 (0.6 – 1.2)
Number of years exposed to excess nitrate-N > 1 mg/L
0	479	433	1.0 (referent)	1.0 (referent)
< 2	50	47	0.9 (0.6 – 1.4)	1.0 (0.6 – 1.5)
2 to < 4	87	69	1.1 (0.7 – 1.6)	1.0 (0.7 – 1.5)
4 to < 6	66	74	0.8 (0.5 – 1.2)	0.7 (0.5 – 1.1)

^a Adjusted for diagnosis/reference year, age at diagnosis/reference year, birth decade, study, vital status, previous breast cancer diagnosis, age at first birth, family history of breast cancer, and education.

^b Adjusted for variables in analysis [a] and years on Cape Cod and years on the Cape squared.