Analysis of hardness of water supply as a risk factor for AK
| Domestic water supply | |||
|---|---|---|---|
| Soft | Medium | Hard | |
| Test of trend in risk:χ2 = 15.62, p = 0.00. | |||
| AK cases | 10 | 10 | 60 |
| Non-cases | 16 439 752 | 8 976 160 | 29 265 203 |
| Risk per million people* | 0.61 | 1.11 | 2.05 |
| Relative risk | 1.0 (referent) | 1.83 | 3.37 |
| (95% confidence limits) | 0.76 to 4.40 | 1.73 to 6.58 | |
| p Value | 0.2406 | 0.00 | |