Microbiological guideline values for recreational bathing in Canada: Time for change?

Recreational bathing is an activity practiced by thousands of Canadians every year. While its health benefits are numerous, bathing in polluted water can also be a source of health problems. These problems are generally nonspecific and are difficult to detect through usual health monitoring systems. Most involve ear and eye ailments, febrile respiratory illness and, particularly, gastroenteritis. In 1992, Health Canada recommended microbiological guideline values for recreational water quality. The values are based on the presence of fecal indicator bacteria, namely, enterococci for marine water, and Escherichia coli or fecal coliforms for fresh water. In marine water, the guideline value is set at 35 enterococci/100 mL, while in fresh water, the standard is 200 E coli/100 mL or 200 fecal coliforms/100 mL when experience demonstrates that over 90% of the fecal coliforms are E coli. Notwithstanding certain variances, many Canadian provinces apply these guidelines. However, in Ontario, the guideline is 100 E coli/100 mL. Over the past several years, many epidemiological studies, including randomized clinical trials, have examined the relationship between bathing in polluted water and ensuing health problems. On review of this literature, the Canadian guideline values for marine water seems appropriate, but scientific evidence argues toward lowering the Canadian guideline values for fresh water to 100 E coli/100 mL, in line with the standard currently in effect in Ontario.