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Regulatory Alert - RA 04-11 - AMSA MEMORANDUM ON POTENTIAL CSO AND SSO HEALTH EFFECTS

Member Pipeline - Regulatory - Alert (RA 04-11)

To: Members & Affiliates, Wet Weather Issues Committee
From: National Office
Date: May 11, 2004
Subject: AMSA MEMORANDUM ON POTENTIAL CSO AND SSO HEALTH EFFECTS
Reference: RA 04-11
Attachment: AMSA’s Technical Memorandum (PDF, ~240 KB)

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The Association of Metropolitan Sewerage Agencies (AMSA) is making available to its members and other interested parties a technical memorandum entitled “Characterization of the Potential Adverse Human Health Effects Associated with Combined Sewer Overflows and Sanitary Sewer Overflows.” This memo was prepared for AMSA by EOA, Inc. The memorandum details the results of an investigation conducted by EOA to collect available technical data and information and, to the extent feasible, assess the potential human health effects associated with combined and sanitary sewer overflows (CSOs and SSOs). AMSA commissioned the study using its Technical Action Fund in an effort to evaluate available information in support of the Association’s response to EPA’s pending Report to Congress on the impacts and control of CSOs and SSOs. EPA’s Report to Congress will be the last in a series of reports required by the Wet Weather Water Quality Act of 2000 on the issue of overflows. EPA anticipates completing the report in the next few weeks. The report will investigate environmental and human health impacts of CSOs and SSOs, resources spent by municipalities to control these impacts, and available control technologies. AMSA will be responding to the Agency’s report once released.

AMSA’s technical memorandum is available for download on the Association’s website. (http://www.amsa-cleanwater.org/private/regalerts/ra04-11a.pdf) It is important to note that this memorandum is only a preliminary examination of potential human health effects. Since the available data on viable pathogens in overflows and actual exposure to overflow events are limited, the results of the evaluation are limited in their application. It is AMSA’s intent to pursue additional projects either through the Technical Action Fund or in cooperation with the Water Environment Research Foundation to answer some of the questions raised by the memorandum, increase the amount of available data on the presence, viability and infectivity of pathogens in CSOs and SSOs, and conduct site-specific exposure analyses to evaluate actual human health risk.

AMSA is releasing this memorandum now, before any additional work is done, in an effort to increase the level of understanding regarding the potential health effects of CSOs and SSOs. Members of the research community have expressed an interest in seeing the results and AMSA feels strongly that it is important to bring to bear as much information as possible on the subject. At this point, AMSA has not initiated any additional projects but is actively considering an effort to examine exposure scenarios in several case study communities.

Memorandum Scope and Limitations
In June 2003, AMSA’s Pathogen Workgroup retained the services of EOA, Inc. to conduct a preliminary characterization of potential human health effects associated with CSOs and SSOs. The characterization was based on available pathogen data and the technical memorandum prepared by EOA examined the probability of infection or illness associated with a hypothetical exposure to an SSO or CSO event. For the purposes of this characterization, it was assumed – and this key assumption carries with it distinct limitations – that an individual was actually exposed to some varying amount of SSO or CSO. The probability of that individual becoming infected or ill from a particular pathogen as a result of that ingested quantity of CSO or SSO was then evaluated. The risk characterization is incomplete as it does not evaluate the probability of someone actually being exposed to that particular quantity of CSO or SSO or factor in whether the pathogens present in the CSO or SSO are actually capable of causing infections. EOA’s review found that much of the data needed for such a comprehensive risk assessment is simply not being collected currently. EOA concluded that given the site-specific nature of exposure, the only appropriate way to assess risk associated with overflows is to examine the potential exposure and risk associated with an individual overflow event.

Other limitations of the characterization, as discussed in Section 5.1.2 of the memorandum, include the fact that the viability and/or infectivity of the organisms and the laboratory recovery efficiency in enumerating the levels of organisms were not accounted for in most cases for the available data. These limitations, especially the lack of data and the need to examine exposure on a case-by-case basis, are the major drivers for the potential follow-up projects AMSA is considering pursuing.

Potential Applications
In addition to supporting the Association’ efforts on wet weather issues, the memorandum provides added insight on the current lack of data and should act as a supporting document for several ongoing and future research projects. The memorandum may also be informative for communities that are conducting risk management evaluations. The protection of public health dictates that when more individuals are potentially exposed to pathogens, a greater level of concern and protection is warranted when making risk management decisions. Section 5.2 of the memorandum provides relevant information on risk management considerations given the results of the characterization.

Next Steps and Additional Information
While no projects have been initiated at this point, AMSA intends to pursue additional work either through the Technical Action Fund or in cooperation with the Water Environment Research Foundation to answer some of the questions raised by the memorandum, increase the amount of available data on the presence of viable pathogens in CSOs and SSOs, and conduct site-specific exposure analyses to evaluate actual human health risk. AMSA has formed a Pathogen Workgroup to track and advise the Association on these issues. If you or someone from your agency is interested in joining the Workgroup or would like additional information on the memorandum, please contact Chris Hornback, AMSA’s Director of Regulatory Affairs at 202/833-9106 or chornback@amsa-cleanwater.org.

 

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