Three potential sources of microfungi in a treated municipal water supply system in sub-tropical Australia

Our plain-English summary of Three potential sources of microfungi in a treated municipal water supply system in sub-tropical Australia, by N.B. Sammon, K.M. Harrower, L.D. Fabbro, et al (International Journal of Environmental Research and Public Health, 2011).

The study

• Authors: N.B. Sammon, K.M. Harrower, L.D. Fabbro, R.H. Reed
• Journal: International Journal of Environmental Research and Public Health
• Published: 2011;8(3):713-32
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Some microfungi are known to be opportunistic human pathogens, and there is a body of scientific opinion that one of their routes of infection may be water aerosols. Others have been implicated as causative agents of odours and off-tastes in drinking water. This study was undertaken to investigate three potential sources of microfungi in a treated, oligotrophic municipal water supply system in sub-tropical Australia. Formation of the microfungal component of developing biofilm on hard surfaces in water storage reservoirs was also assessed. Inside and outside air samples were collected from two reservoirs using two types of Burkard air samplers. Biofilm and soft sediment samples were collected from the inner surfaces of asbestos cement water pipes and from pipe dead ends respectively. These were analysed for microfungal growth and sporulation using Calcofluor White stain and epifluorescent microscopy. Artificial coupons of glass, PVC and concrete were immersed in two reservoirs to assess microfungal biofilm formation. This was analysed periodically using Calcofluor White stain and epifluorescent microscopy, cultures of coupon swabs and scanning electron microscopy. Fungal spores were recovered from all air samples. The number of colonies and the genera were similar for both inside and outside air. Microfungal filaments and sporulating structures were recovered from most of the pipe inner surface biofilm and dead end sediment samples, but were sparser in the biofilm than in the sediment samples. No recognisable, vegetative filamentous fungi were found in the slowly developing biofilm on coupons. This study indicates that airborne spores are an important potential source of microfungi found in water storage reservoirs. It has also demonstrated conclusively that filamentous microfungi grow and sporulate on water pipe inner surfaces and in soft sediments within the water distribution system.

In plain English

This was a field study of microscopic fungi (microfungi) in the treated drinking water system of Rockhampton, Central Queensland, Australia. It did not study asbestos exposure or human health. Asbestos cement water pipes appear only as surfaces that were examined for fungal growth. The authors sampled air inside and outside two roofed storage reservoirs. They immersed glass, PVC and concrete test pieces (coupons) in the reservoirs for up to 26 months. They also examined scrapings and fragments from asbestos cement pipe sections collected at five sites, and sediment flushed from six pipe dead ends. The number of fungal spores in air inside the reservoirs was similar to the number outside. No recognisable fungal growth was seen on the coupons. Fungal growth was seen in 10 of the 15 pipe scrapings, on two pipe wall fragments, and in all 18 dead-end sediment samples, where it was more profuse. The authors concluded that several genera of microfungi grow and sporulate on asbestos cement pipe walls, but that the growth was generally sparse. They noted that five pipe sections was a relatively small sample.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental microbiology field study of a municipal water supply system: air sampling, immersed artificial coupons, and microscopy and culture of pipe and sediment samples
• Who was studied: The treated water supply system of Rockhampton, Central Queensland, Australia (population ca. 70,000). The samples were air from two reservoirs (R3 and R4), coupons kept in those reservoirs, asbestos cement pipe sections from five sites, and sediment from six pipe dead ends.
• Exposure: No asbestos exposure was studied. The potential sources of microfungi examined were airborne spores, biofilm on the inner surfaces of asbestos cement distribution pipes, and soft sediment in pipe dead ends.
• Main results:
  • At each of the two reservoirs, the number of microfungal spores in inside air was similar to the number in outside air.
  • No recognisable microfungal growth was seen on any of the glass, PVC or concrete coupons. Coupons were removed at 7 and 11 months, and from reservoir R3 also at 26 months.
  • Asbestos cement pipe wall fragments: microfungal growth was seen on two fragments, one from each of two sites.
  • Asbestos cement pipe wall scrapings: microfungal growth was seen in 10 of 15 samples from the five sites. Definite reproductive structures were seen in 4 of the 15 samples, from three of the five sites.
  • Pipe dead-end sediments: microfungi were seen in all 18 samples from six sites. Definite reproductive structures were seen in 6 of the 18 samples, from four sites. Growth was more profuse than in the pipe wall samples.
• The authors' conclusion: The authors concluded that several presumptively different genera of microfungi grow and sporulate on the walls of asbestos cement pipes, but that the growth and reproductive structures are generally sparse and relatively simple.
• Limitations the authors state:
  • Only five pipe sections were examined, a relatively small sample limited by the maintenance works available.
  • The extent of fungal colonisation of pipe surfaces and sediments could not be assessed accurately.
  • Scraping and swabbing break up fungal colonies, which affects culture counts.
  • Concrete coupons were difficult to examine under fluorescence microscopy.
  • Fungi were identified only to genus level.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Scanning Electron Microscopy (SEM).

Related studies

• The need to control asbestos fibers in potable water supply systems — J.R. Millette, R.L. Boone, et al. (1981)
• Detection of virus in water: sensitivity of the tentative standard method for drinking water — W.F. Hill, W. Jakubowski, et al. (1976)
• Factors associated with the isolation of Nontuberculous mycobacteria (NTM) from a large municipal water system in Brisbane, Australia — R.M. Thomson, R. Carter, et al. (2013)
• Asbestiform amphibole minerals: detection and measurement of high concentrations in municipal water supplies — P.M. Cook, G.E. Glass, et al. (1974)
• Analysis of amphibole asbestiform fibers in municipal water supplies — W.J. Nicholson (1974)
• An investigation of the use of asbestos cement pipe for public water supply and the incidence of gastrointestinal cancer in Connecticut, 1935-1973 — J.M. Harrington, G.F. Craun, et al. (1978)

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