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Journal of Environmental Quality Abstract - Special Sections: Environmental Standards for Agricultural Watersheds

Investigation of an Escherichia coli Environmental Benchmark for Waterborne Pathogens in Agricultural Watersheds in Canada


This article in JEQ

  1. Vol. 41 No. 1, p. 21-30
    Received: June 7, 2010

    * Corresponding author(s): tom.edge@ec.gc.ca
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  1. T. A. Edge *a,
  2. A. El-Shaarawia,
  3. V. Gannonb,
  4. C. Jokinenb,
  5. R. Kentc,
  6. I. U. H. Khana,
  7. W. Koningd,
  8. D. Lapene,
  9. J. Millerf,
  10. N. Neumanni,
  11. R. Phillipsc,
  12. W. Robertsonj,
  13. H. Schreierk,
  14. A. Scottg,
  15. I. Shtepanii,
  16. E. Toppg,
  17. G. Wilkese and
  18. E. van Bochoveh
  1. a Water Science & Technology, National Water Research Institute, Environment Canada, Burlington, ON L7R 4A6, Canada
    b Public Health Agency of Canada, Laboratory for Foodborne Zoonoses, Lethbridge, AB T1J 3Z4, Canada
    c National Water Quality Monitoring Office, Environment Canada, Gatineau, QC K1A 0H3, Canada
    d Alberta Environment, Calgary, AB T2E 7L7, Canada
    e Agriculture and Agri-Food Canada, Ottawa, ON K1A 0C6, Canada
    f Agriculture and Agri-Food Canada, Lethbridge, AB T1J 4B1, Canada
    i Univ. of Alberta, Edmonton, AB T6G 2G3, Canada
    j Health Canada, Ottawa, ON K1A 0K9, Canada (retired)
    k Univ. of British Columbia, Vancouver, BC V6T 1Z4, Canada. Assigned to Associate Editor A. Mark Ibekwe
    g Agriculture and Agri-Food Canada, London, ON N5V 4T3, Canada
    h Agriculture and Agri-Food Canada, Quebec, QC G1V 2J3, Canada


Canada's National Agri-Environmental Standards Initiative sought to develop an environmental benchmark for low-level waterborne pathogen occurrence in agricultural watersheds. A field study collected 902 water samples from 27 sites in four intensive agricultural watersheds across Canada from 2005 to 2007. Four of the sites were selected as reference sites away from livestock and human fecal pollution sources in each watershed. Water samples were analyzed for Campylobacter spp., Salmonella spp., Escherichia coli O157:H7, Cryptosporidium spp., Giardia spp., and the water quality indicator E. coli. The annual mean number of pathogen species was higher at agricultural sites (1.54 ± 0.07 species per water sample) than at reference sites (0.75 ± 0.14 species per water sample). The annual mean concentration of E. coli was also higher at agricultural sites (491 ± 96 colony-forming units [cfu] 100 mL−1) than at reference sites (53 ± 18 cfu 100 mL−1). The feasibility of adopting existing E. coli water quality guideline values as an environmental benchmark was assessed, but waterborne pathogens were detected at agricultural sites in 80% of water samples with low E. coli concentrations (<100 cfu 100 mL−1). Instead, an approach was developed based on using the natural background occurrence of pathogens at reference sites in agricultural watersheds to derive provisional environmental benchmarks for pathogens at agricultural sites. The environmental benchmarks that were derived were found to represent E. coli values lower than geometric mean values typically found in recreational water quality guidelines. Additional research is needed to investigate environmental benchmarks for waterborne pathogens within the context of the “One World, One Health” perspective for protecting human, domestic animal, and wildlife health.

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