Volume 12, Number 4—April 2006
Research
Reducing Legionella Colonization of Water Systems with Monochloramine
Table 3
Factors associated with Legionella colonization of water heaters in sampled buildings, San Francisco, California
Factor | No. samples | % Legionella colonization | Adjusted prevalence ratio (95% CI)* | p value |
---|---|---|---|---|
Residual disinfectant | ||||
Chlorine | 157 | 29 | Referent | |
Chloramine | 159 | 1 | 0.04 (0.01–0.21) | <0.001 |
Water heater temperature, °C | ||||
<30 | 29 | 21 | Referent | |
30–39 | 68 | 24 | 0.43 (0.27–0.70) | 0.001 |
40–49 | 131 | 18 | 0.27 (0.16–0.46) | 0.001 |
>50 | 88 | 1 | 0.09 (0.05–0.18) | 0.001 |
Building height (stories) | ||||
3–10 | 215 | 11 | Referent | |
>10 | 101 | 24 | 2.96 (1.51–5.79) | 0.002 |
Disruption in service in last 3 mo | ||||
Yes | 39 | 26 | 2.26 (1.31–3.88) | 0.003 |
No | 277 | 13 | Referent |
*Prevalence ratios and 95% confidence intervals (CIs) were adjusted for repeated sampling and for effects of all other variables.