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INFERENCES DRAWN FROM A RISK ASSESSMENT COMPARED DIRECTLY TO A RANDOMIZED TRIAL OF A HOME DRINKING WATER INTERVENTION
Citation:
S. EISENBERG, J. N., A. HUBBARD, T. J. WADE, M. D. SYLVESTER, M. W. LECHEVALLIER, D. A. LEVY, AND J. M. COLFORD. INFERENCES DRAWN FROM A RISK ASSESSMENT COMPARED DIRECTLY TO A RANDOMIZED TRIAL OF A HOME DRINKING WATER INTERVENTION. ENVIRONMENTAL HEALTH PERSPECTIVES. National Institute of Environmental Health Sciences (NIEHS), Research Triangle Park, NC, 114(8):1199-1204, (2006).
Impact/Purpose:
to compare direct risk estimates of waterborne disease from the intervention trial with indirect estimates from a risk assessment
Description:
Risk assessments and intervention trials have been used to inform the EPA on drinking water risks. Seldom are both methods used concurrently. Between 2001 and 2003, illness data from a trial were collected simultaneously with exposure data, providing a unique opportunity to compare direct risk estimates of waterborne disease from the intervention trial with indirect estimates from a risk assessment. Comparing the active vs. sham groups, the estimated attributable (annual) disease rate from the trial provided no evidence of a significantly elevated drinking water risk (AR = -365, sham minus active; 95 percent confidence interval: 2555, 1825),. The predicted mean rate of disease per 10,000 from the risk assessment was 13.9 (2.5 and 97.5 percentile: 1.6, 28.7) assuming four log-removal due to viral disinfection and 5.5 (2.5 and 97.5 percentile: 1.4, 19) assuming six log-removal. Risk assessments are important under situations of low risk when estimates are difficult to attain from trials. Trials provide direct risk estimates and even if not statistically significant, the upper confidence interval estimates are informative upper estimates of likely risk. Consistent results of the risk assessment and trial are encouraging suggesting that conclusions about waterborne disease risk may be strengthened by the joint use of these two approaches.