Table 3.
Associations between average trihalomethanes and haloacetic acids in public water supplies and incident colon and rectal cancers, Iowa Women’s Health Study participants >10 years at their drinking water source (N=15,532a)
| Colon | Rectum | ||||
|---|---|---|---|---|---|
| N | Cases | HRb, 95% CI | Cases | HRb, 95% CI | |
| CHCl3 (μg/L) | |||||
| 0.60 | 3,358 | 157 | 1.00 (Ref.) | 30 | 1.00 (Ref.) |
| 0.60–1.85 | 3,659 | 134 | 0.90 (0.72, 1.4) | 32 | 1.13 (0.70, 1.87) |
| 1.86–8.41 | 3,623 | 137 | 0.94 (0.75, 1.19) | 45 | 1.68 (1.05, 2.70) |
| >8.41 | 4,392 | 184 | 1.08 (0.86, 1.34) | 48 | 1.52 (0.95, 2.45) |
| p trend | 0.17 | 0.25 | |||
| Continuousc | 1.03 (0.99, 1.08) | 1.12 (1.03, 1.22) | |||
| BDCM (μg/L) | |||||
| <0.25 | 4,741 | 178 | 1.00 (Ref.) | 31 | 1.00 (Ref.) |
| 0.25–1.16 | 3,328 | 139 | 1.14 (0.92, 1.43) | 38 | 1.76 (1.10, 2.84) |
| 1.17–3.78 | 3,793 | 141 | 1.03 (0.81, 1.30) | 44 | 1.99 (1.22, 3.25) |
| >3.78 | 3,670 | 154 | 1.16 (0.94, 1.45) | 42 | 1.87 (1.17, 3.00) |
| p trend | 0.30 | 0.09 | |||
| Continuous | 1.03 (0.98, 1.09) | 1.16 (1.04, 1.28) | |||
| DCAA (μg/L) | |||||
| <1.65 | 4,206 | 169 | 1.00 (Ref.) | 35 | 1.00 (Ref.) |
| 1.65–2.27 | 2,864 | 97 | 0.83 (0.65, 1.07) | 27 | 1.11 (1.67, 1.84) |
| 2.28–4.84 | 4,259 | 153 | 0.90 (0.73, 1.13) | 46 | 1.31 (0.84, 2.03) |
| >4.84 | 4,203 | 193 | 1.17 (0.95, 1.44) | 47 | 1.34 (0.87, 2.08) |
| p trend | 0.01 | 0.32 | |||
| Continuous | 1.07 (1.00, 1.16) | 1.13 (0.98, 1.31) | |||
| TCAA (μg/L) | |||||
| <0.25 | 4,673 | 181 | 1.00 (Ref.) | 30 | 1.00 (Ref.) |
| 0.25–0.63 | 1,900 | 68 | 0.94 (0.71, 1.25) | 21 | 1.70 (0.99, 2.98) |
| 0.64–1.69 | 5,249 | 199 | 1.02 (0.82, 1.25) | 61 | 1.94 (1.24, 3.05) |
| >1.69 | 3,710 | 164 | 1.20 (0.97, 1.49) | 43 | 1.92 (1.20, 3.09) |
| p trend | 0.05 | 0.18 | |||
| Continuous | 1.03 (0.99, 1.08) | 1.14 (1.04, 1.25) | |||
| BCAA (μg/L) | |||||
| <0.1 | 6,289 | 230 | 1.00 (Ref.) | 49 | 1.00 (Ref.) |
| 0.1–0.94 | 2,449 | 83 | 0.96 (0.74, 1.23) | 33 | 1.79 (1.15, 2.79) |
| 0.95–1.89 | 4,012 | 161 | 1.17 (0.94, 1.46) | 43 | 1.52 (0.97, 2.38) |
| >1.89 | 3,160 | 138 | 1.26 (1.01, 1.57) | 30 | 1.30 (0.81, 2.08) |
| p trend | 0.03 | 0.87 | |||
| Continuous | 1.10 (0.99, 1.23) | 0.92 (0.76, 1.11) | |||
| HAA5 (μg/L) | |||||
| <0.1 | 3,869 | 163 | 1.00 (Ref.) | 34 | 1.00 (Ref.) |
| 0.1–0.94 | 3,178 | 104 | 0.78 (0.61, 1.00) | 26 | 0.95 (0.57, 1.59) |
| 0.95–1.89 | 4,539 | 164 | 0.86 (0.70, 1.08) | 51 | 1.30 (0.84, 2.01) |
| >1.89 | 3,946 | 181 | 1.12 (0.91, 1.39) | 44 | 1.29 (0.82, 2.03) |
| p trend | 0.05 | 0.33 | |||
| Continuous | 1.06 (0.99, 1.13) | 1.14 (1.01, 1.29) | |||
| HAA6 (μg/L) | |||||
| <0.1 | 3,921 | 159 | 1.00 (Ref.) | 32 | 1.00 (Ref.) |
| 0.1–0.94 | 4,878 | 166 | 0.84 (0.68, 1.05) | 50 | 1.27 (0.81, 1.99) |
| 0.95–1.89 | 2,795 | 108 | 0.98 (0.76, 1.27) | 27 | 1.26 (0.74, 2.14) |
| >1.89 | 3,938 | 179 | 1.16 (1.16, 1.43) | 46 | 1.46 (0.93, 2.31) |
| p trend | 0.02 | 0.18 | |||
| Continuous | 1.06 (1.00, 1.13) | 1.15 (1.02, 1.29) |
a
After excluding 378 participants with missing covariate data.
b
All models adjusted for age, physical activity, smoking status, and mutually adjusted for NO3-N.
c
Per 1-unit change in natural log-transformed value.
CHCl3, chloroform; BDCM, bromodicholoromethane; DCAA, dichloroacetic acid; TCAA, trichloroacetic acid; HAA5 and HAA6, haloacetic acids; BCAA, bromochloroacetic acid.