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Using a technique developed to track pathogens in sewage, a California Sea Grant-funded researcher showed that harmful human viruses are contaminating coastal waters at major river mouths in southern California.
Tests have not determined whether the viruses are virulent, but their presence does indicate that human waste is making its way into urban waterways. Because of the health risks associated with human waste, some groups are beginning to test their creeks and drainage culverts for signs of human contamination.
The risk of contamination from human waste appears to be significant, according to a survey of 12 river mouths in Los Angeles, Orange and San Diego counties conducted by assistant professor Sunny Jiang at the University of California, Irvine. In the 1999 survey, also funded by California Sea Grant, Jiang reports that four of the 12 sites sampled tested positive for the presence of the human adenovirus: the Los Angeles, San Gabriel, Santa Ana and Tijuana river mouths.
Of these four only the Los Angeles river mouth also registered as having high fecal bacteria levels, the standard criteria for evaluating water quality, closing beaches and monitoring compliance with federal clean water laws.
Because the presence of the virus did not correspond with high bacteria counts, Jiang said she believes the current water quality standards are "not adequately indicating human health risks."
"The presence of the virus does not correlate with high levels of bacteria," Jiang said. "Therefore, you don't have a beach closure and are potentially exposing people to health risks."
There are more than 100 viruses found in human waste that can survive for as long as 130 days in seawater. None of these are tracked in routine tests by California health officials.
Jiang's findings and those of her colleagues are published in the January 2001 issue of Applied and Environmental Microbiology.