In the May 2002 issue of Journal AWWA,
Stewart and co-workers summarized an investigation that
addresses the potential health consequences related to
consuming water from a reservoir at which body-contact
recreation is permitted (Stewart et al, 2002). The investigation
used a water quality model to estimate pathogen
loading from recreationists and to calculate predicted
pathogen concentrations at the outlet tower of the reservoir.
Based on those data, risk to drinking water consumers
was predicted. The authors reported that the annual
risk of waterborne illness would increase three times above
background, despite conventional water treatment before
distribution as potable water.
Although the authors used a powerful combination of
modeling techniques for assimilating a wide range of disparate
data, the substantial uncertainty associated with
the model parameters most directly affecting risk is not
articulated and/or analyzed in the findings of the investigation.
The unspecified effect of uncertainty in this investigation
casts doubts on the conclusions. These uncertainty issues, furthermore, suggest that the use of the Stewart et al document as guidance for policymakers and stakeholders who are examining issues associated with body-contact recreation and drinking water should be reexamined.
The authors raised the fact that high levels of uncertainty may affect the analysis. They report: "The model
was highly sensitive to parameters associated with
pathogen loading" (page 87). Pathogen loading to the
reservoir was assumed to occur in two ways: shedding
of residual fecal material from recreationists' bodies upon
contact with the water (shedding); and, accidental fecal
releases (AFRs) and therefore was computed as a function
of the number of infected individuals recreating in the
reservoir. The percentages of recreationists assumed to be
infected in each simulation varied by pathogen as follows:
Cryptosporidium 0-5%, rotavirus 5-20%, Giardia
0-10%, and poliovirus 5-20%, and the frequency of an
AFR was 0-0.2%. This discussion focuses on parameter
estimates for Cryptosporidium prevalence, rotavirus
prevalence, and AFRs as well as the risk management
implications of those ranges.
Includes 13 references.
| Edition : | Vol. 95 - No. 1 |
| File Size : | 1
file
, 200 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 3 |
| Published : | 01/01/2003 |
