Influence of Air Quality on the Composition of Microbial Pathogens in Fresh Rainwater

Abstract

In this study, the microbiological quality of fresh rainwater was assessed from 50 rain events under tropical weather conditions for a year. The levels of four major opportunistic waterborne pathogens, namely, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Aeromonas hydrophila, in rainwater samples were quantified by using a robust and sensitive quantitative PCR (qPCR) method. Of the 50 rainwater samples, 25 were found to be positive for at least one pathogen: 21 for E. coli, 16 for P. aeruginosa, 6 for K. pneumoniae, and 1 for A. hydrophila. In addition to the microbiological assessment of rainwater samples, we also studied the influence of prevailing air quality on the microbial quality of rainwater over the sampling period. A significant change in the diversity and relative abundance of the basic microbial indicator organisms in rainwater was observed during a major regional air pollution episode in Southeast Asia due to biomass-burning emissions. Water shortage is becoming a major problem worldwide due to the increased demands of growing population and urbanization (29,38). In an effort to ensure a sustainable future, a global search for alternative sources of water is ongoing, and rainwater harvesting has received considerable attention (1,13,23,44,45). However, the use of rainwater for drinking purposes is impeded by issues of water quality in terms of chemical and microbiological contamination and its potential health risks (1). While numerous studies on the chemical contamination of rainwater have been conducted (5,11,27,30,43), its microbial quality remains relatively unknown due to the analytical challenge involved in the detection of a range of contaminants, particularly pathogens.Some previous studies have reported that roof-harvested rainwater is generally acceptable for drinking and household purposes (12,13,16,26), while more-recent studies have revealed the presence of waterborne pathogens in rainwater samples (1,3,11,22,34,35,43). Differences in the characteristics of the catchment area, the type of water tanks, their cleanliness, and other factors, such as roof material, the intensity of human activities in the catchment area (urban or rural), and the presence of insects and birds on the rooftop, could be responsible for the contradictory results in the literature on the microbial quality of rainwater (10,17,18,34,39,46). Numerous studies conducted on the chemical composition of rainwater and roof runoff have demonstrated links between chemical contaminants and weather patterns, and between atmospheric transport and deposition (9,19,24,48). However, little is known about such links with respect to microbial composition. In order to identify sources of microorganisms in roof-harvested rainwater, it is desirable to study the microbial flora of fresh rainwater prior to its collection and storage, with no contamination from external sources.Microbial water quality monitoring is generally directed toward indicator microorganisms such as coliforms, Escherichia coli, and Klebsiel...

Prevalence of Virulence Genes Associated with Pathogenic Escherichia coli Strains Isolated from Domestically Harvested Rainwater during Low- and High-Rainfall Periods

“…Other sources of rainwater contamination include "leaf debris and organic material washed into the tank, animals, insects, and birds that have drowned in the water and breeding mosquitoes" (37). A recent study conducted in Singapore confirmed the presence of pathogenic microorganisms, including E. coli, in airborne particulate matter, which can serve as another source of contamination (38). A gravel road also runs along the outside of the settlement, and with cars passing by on a regular basis, dust could be disturbed and settle on the roof surface, resulting in contamination.…”

Evaluation of a silver-ion based purification system for rainwater harvesting at a small-scale community level

“…Results were analysed and compared with the original data set, obtaining further insights on both the silver-ion system and the installation as a whole. Our focus was on system performance and not on the incoming rainwater quality per se, which tends to vary seasonally along with a number of complex factors such as weather and air quality (Evans et al 2006;Kaushik et al 2012). Although both studies were started in different periods (April 2010 andSeptember 2012), this in itself would not present enough data for a proper time variability evaluation.…”

Antibiotic resistance in Escherichia coli isolates from roof-harvested rainwater tanks and urban pigeon faeces as the likely source of contamination

“…Previous research on the influence of prevailing air quality in the environment surrounding a rainwater harvesting site, have suggested air quality to play an important role in influencing the microbial quality of rainwater (Evans et al 2006;Kaushik et al 2012). The link between air quality and the microbial quality of rainwater under different weather conditions have been suggested as one of the reasons for discrepancies in reported literature concerning rainwater portability.…”

“…The link between air quality and the microbial quality of rainwater under different weather conditions have been suggested as one of the reasons for discrepancies in reported literature concerning rainwater portability. For instance, research by Kaushik et al, (2012) on rainwater contamination factors that are independent of external sources of contamination such as those encountered with roof-harvesting methods found E. coli to be one of the microorganisms present in fresh rainwater and contributing to its microbial diversity.…”