Table 2.
Cumulative cancer risk for community water systems in California grouped by system size.
| Community Water System Size | Demographic Group Defined by the U.S. Census Bureau | Tercile Boundaries for Percentage of Population within a Demographic Group 1 | Total Population in the Tercile, Millions (Rounded) | Median Cumulative Cancer Risk | Jonckheere-Terpstra Trend Test p-Value 2 |
|---|---|---|---|---|---|
| Small (501–3300) |
Black or African American | ≤0.5% (T1) | 0.21 | 4.3 × 10−4 | 0.1333 |
| 0.5–2.2% (T2) | 0.21 | 3.5 × 10−4 | |||
| ≥2.2% (T3) | 0.23 | 5.9 × 10−4 | |||
| Hispanic or Latino | ≤14.3% (T1) | 0.21 | 4.4 × 10−4 | 0.0431 * | |
| 14.4–30.6% (T2) | 0.22 | 4.9 × 10−4 | |||
| ≥30.9% (T3) | 0.21 | 4.9 × 10−4 | |||
| Medium (3301–10,000) |
Black or African American | ≤0.7% (T1) | 0.43 | 5.9 × 10−4 | 0.6883 |
| 0.7–2.5% (T2) | 0.46 | 5.8 × 10−4 | |||
| ≥2.6% (T3) | 0.45 | 6.6 × 10−4 | |||
| Hispanic or Latino | ≤20.9% (T1) | 0.42 | 5.8 × 10−4 | 0.4065 | |
| 20.9–43.2% (T2) | 0.46 | 6.7 × 10−4 | |||
| ≥43.6% (T3) | 0.45 | 6.0 × 10−4 | |||
| Large (10,001–100,000) |
Black or African American | ≤1.5% (T1) | 3.1 | 6.7 × 10−4 | 0.1625 |
| 1.5–3.7% (T2) | 4.2 | 6.7 × 10−4 | |||
| ≥3.8% (T3) | 3.7 | 7.8 × 10−4 | |||
| Hispanic or Latino | ≤23.0% (T1) | 3.6 | 7.2 × 10−4 | 0.1183 | |
| 23.3–44.1% (T2) | 3.8 | 8.0 × 10−4 | |||
| ≥44.5% (T3) | 3.6 | 5.8 × 10−4 | |||
| Very Large (>100,000) |
Black or African American | ≤2.6% (T1) | 4.6 | 5.6 × 10−4 | 0.0041 * |
| 2.7–6.4% (T2) | 6.8 | 6.8 × 10−4 | |||
| ≥6.7% (T3) | 10.8 | 7.6 × 10−4 | |||
| Hispanic or Latino | ≤30.0% (T1) | 6.4 | 6.9 × 10−4 | 0.7324 | |
| 30.1–47.7% (T2) | 10.2 | 6.9 × 10−4 | |||
| ≥48.0% (T3) | 5.6 | 6.5 × 10−4 |
1 The tercile boundaries are indicated with a single decimal digit and may appear to overlap due to rounding; actual tercile boundaries were defined with multiple decimal digits and do not overlap. 2 Trend test p values less than 0.05 are considered statistically significant and are marked with an asterisk (*).