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Dog waste poses threat to water

USA TODAY - June 6, 2002
Written By Traci Watson,

Cities struggle with 'dog piles.' Where they're cracking down:

In San Diego. The city spent roughly $10,000 on extra trash cans, nagging signs and plastic "mutt mitts" at its Dog Beach, where the surf was closed to swimmers 125 times in 2000. The measures led to "measurably fewer dog piles. That's the term we use," says Ted Medina, deputy director for coastal parks. He estimates the beach is 30%-40% cleaner than it was before the effort started late last year.

In Chattahoochee River National Recreation Area near Atlanta. Bacteria levels in the river exceed standards so often that a Web site tells would-be boaters and swimmers whether the river is safe on any given day. To help clean it up, park officials recently started giving tickets to visitors who have dogs but no doggie bags.

In Boulder, Colo. Here the problem wasn't dirty water but the nitrogen in dog droppings. Native grasses in the city's mountain parks are used to low-nitrogen conditions. But with dogs doing their business, weeds were muscling aside the grasses. The city did 10 months of education before starting to hand out $100 fines last year. Boulder officials had to convince residents that dog waste "is not fertilizer," says Mike Patton, co-director of open space and mountain parks. "Some people really did believe it was."

For as long as the dog has been man's best friend, dog waste has posed a menace to man's nose and foot. Now science has revealed a more unsavory truth: It's an environmental pollutant.

In the mid-1990s, scientists perfected methods for tracking the origin of nasty bacteria in streams and seawater. From Clearwater, Fla., to Arlington, Va., to Boise the trail has led straight to the hunched-up dog and to owners who don't pick up after their pets.

At some beaches, dogs help raise bacteria levels so high that visitors must stay out of the water. Goaded by such studies, some cities have directed as much as $10,000 in the last few years to encourage dog owners to clean up after their pets. A few municipalities have started issuing citations to those who ignore pet clean-up ordinances.

Many dog lovers are in denial about their pooches' leavings. But researchers have named the idea that areas used by dogs pump more bacteria into waterways - the "Fido hypothesis."

Dogs are only one of many fixtures of suburban America that add to water pollution. Lawn fertilizers, rinse water from driveways and motor oil commonly end up in streams and lakes.

But unlike those sources, dogs generate disease-causing bacteria that can make people sick. Studies done in the last few years put dogs third or fourth on the list of contributors to bacteria in contaminated waters. "Dogs are one of our usual suspects," says Valerie Harwood, a microbiologist at the University of South Florida. "At certain sites, we find their effect to be significant."

It doesn't take a Ph.D. to figure out that dog do is nasty. But it took science to determine how nasty it is.

From mutt to blue-blooded champion, all dogs harbor so-called coliform bacteria, which live in the gut. The group includes E. coli, a bacterium that can cause disease, and fecal coliform bacteria, which spread through feces. Dogs also carry salmonella and giardia. Environmental officials use measurements of some of these bacteria as barometers of how much fecal matter has contaminated a body of water.

This wouldn't matter if pet dogs were as rare as pet chinchillas. But four in 10 U.S. households include at least one dog, according to the American Pet Products Manufacturers Association. The association's statistics also show that Americans owned 54.6 million dogs in 1996 and 68 million dogs in 2000. Of that total, 45% were "large" dogs - 40 pounds or more.

Those numbers add up to a lot of kibble. That wouldn't matter if all dog owners also owned a pooper-scooper. But several studies have found that roughly 40% of Americans don't pick up their dogs' feces (women are more likely to do so than men).

New analysis provides answers

The environmental impact of dog waste went unrecognized for decades. Then scientists developed lab techniques to determine the origin of fecal bacteria contaminating water. One method is a variant of DNA fingerprinting. Another method looks at the antibiotic resistance of microbes from different species.

Scientists caution that the methods are still new. They are able to distinguish between major and minor sources of pollution, but they can't say with precision whether dogs contribute 20% or 30% of the pollution in a stream. "There's inherently some error," says Don Stoeckel, a microbiologist for the Ohio district of the U.S. Geological Survey who's studying bacteria-tracking methods. "I think the best (they) can do is give you some evidence of the magnitude of each source."

Nonetheless, Stoeckel says, the analytical tools do provide useful information. Researchers have studied dozens of waterways. Wild birds and humans usually head the roster of who's fouling the water. But in some areas, dogs make significant deposits.

At Morro Bay, Calif., for example, dogs contribute roughly 10% of the E. coli, says Christopher Kitts, a microbiologist at California Polytechnic State University-San Luis Obispo. "And that can be the difference between a beach closing and a beach not closing," he says.


This page is part of the Dog Waste section of New Animal Control.Org