An assessment of, and response to, potential cross-contamination routes due to defective appliance water trap seals in building drainage systems

Abstract

The outbreak of severe acute respiratory syndrome (SARS), centred on Southeast Asia in 2002 and 2003, sparked fears of an uncontrollable pandemic. The outbreak at one housing complex in Hong Kong resulted in a disproportionately large number of cases with 321 people contracting the virus, resulting in 42 fatalities. This outbreak led to an investigation by World Health Organisation, which firmly laid the blame for the spread of the virus in the housing complex on defects in the building drainage and vent system. The mode of viral transmission was identified as due to airborne aerosolised particles from virus-laden excreta emanating from the drainage system. The aerosolised particles were allowed to enter the habitable space through empty water trap seals which are the main protection against such ingress in a building drainage and vent system. This research reports on the defective trap identification system developed to provide a means of testing the seal afforded by the water trap seal in buildings. This innovative sonar-like technology incorporates a means of identifying compromised water trap seals anywhere in a building in a repeatable, non-destructive manner. While the technology has been effectively validated by a combination of laboratory investigation, site testing and numerical simulation, the rationale for the need to monitor water trap seals is less obvious to professionals operating in this field. This article addresses this issue and presents such a rationale, identifying some of the harmful pathogens which could lead to cross-contamination from person to person via the building drainage system. Practical applications: The research carried out in this area has highlighted the lack of any real monitoring of water trap seal status in buildings and has put the issue firmly on the agenda for consideration by building owners, operators and regulators, for whom the building drainage and vent system has long been categorised as 'fit and forget'. The inspiration for this study was the response to the SARS outbreak which began in 2002. The case to monitor this important seal is clearly made and whilst the predicted pandemic of the SARS virus failed to materialise on an extended time frame and the outbreak has largely been consigned to history, it should serve as a constant reminder to professionals in the industry that we 'fit and forget' at our peril.

Pathogen cross-transmission via building sanitary plumbing systems in a full scale pilot test-rig

“…While research into the potential mechanisms of the SARS transmission at Amoy Gardens proved that there was an airflow path between the sanitary plumbing system and different parts of the building when the U-trap had no water seal [ 14 , 15 ], it was only hypothesised that pathogens could be transmitted within these airflows and could deliver an infective exposure dose. This paper sets out to test the WHO hypothesis by qualitatively and quantitatively tracking the transmission of a model organism chosen to represent pathogens generally within the airflows of a full scale pilot test-rig representing a two storey sanitary plumbing system designed to current European standards [ 16 ].…”

Aerosol-Transmitted Infections—a New Consideration for Public Health and Infection Control Teams

“…In these apartments, floor drains in the bathrooms had a direct connection to the sewer pipes running down the outside of these buildings. However, when not filled with water, it was possible for sewage-contaminated aerosols to leak back into the bathroom-particularly if the extraction fans were on-to contaminate the apartment air and then to be extracted out into the gaps between the tower blocks [25]. Virus-contaminated aerosols could then be carried up on the upwelling air between the tower blocks and enter apartments in the adjacent towers through other open windows if kitchen or bathroom extraction fans were operating, creating a negative pressure sink within these apartments.…”

SARS-CoV-2 in environmental perspective: Occurrence, persistence, surveillance, inactivation and challenges

“…Atmospheric loading of CoV as aerosols from wastewater provides a more direct route for human exposure [47] which is so far less understood. The virus that enters the sewer systems forms virus-laden aerosols [7] through mechanisms of cross-contamination [108] , [109] . Unit operation in WWTP such as biological oxidation normally employed for treatment of sewage/wastewater influences the aerosol formation due to aeration operation.…”