Voice of San Diego: What's in TJ Sewage?

VOICE OF SAN DIEGO

By ROB DAVIS
Voice Staff Writer
Monday, April 17, 2006

One day last November, enough copper got swept into Tijuana's
overwhelmed sewer system to have minted about 7,700 pennies. And that's
just what got collected in a city where thousands lack basic sewers.

It isn't unusual. The metal comes from scraping brake pads, from
junkyards, gutters and industry. It wasn't the only metal coursing
through the city's sewers that day, according to monthly monitoring
reports. Almost seven pounds of lead were caught. So were nine pounds
of nickel -- enough to mint 800 of the five-cent pieces.

Despite the public health debate over Tijuana's storm-water runoff, few
people have actually quantified what's in the frothy brew that gets
swept into the Pacific Ocean. But a look into Tijuana's sewers gives
some insight, as the runoff that's collected by the sewer system is
likely similar to the runoff that makes its way into the ocean.

Metals are in the mix. The chemical components of gasoline can be
found. So can pesticides, fecal material, bacteria and viruses such as
Hepatitis A.

A voiceofsandiego.org review of the components of Mexican sewage
treated by a sewage plant opened a window into revealing what escapes
treatment and often winds up in the Pacific. Estimates vary, but
somewhere between 15 percent and 50 percent of Tijuana's residents lack
sewers. Much of their waste -- fecal material, bath water, dish
detergents -- gets dumped in the streets, destined for the ocean. Leaks
and sewage overflows complicate the problem.

But broad, sweeping data about the runoff's ingredients is hard to find
and has to be pieced together. Aside from the work of San Diego State
University environmental health professor Richard Gersberg, his
students, and San Diego County officials, it appears little has been
done to comprehensively quantify everything that's in the mess.

Gersberg, who teaches at SDSU's School of Public Health, said Mexican
runoff can have disease levels twice as high as in San Diego, making
pathogens -- not metals or other pollutants -- the contaminant that
poses the greatest threat to human health. Gersberg questions the
common assertion that Mexican runoff is rifer with metals and
industrial pollutants than in the United States.

"I think a lot of it is just anecdotal information or what people
fear," he said. The common refrain that Mexican industries and
maquiladoras are simply dumping chemicals down their drains "is not
based on any data," he said. "I'm sure it happens, but I haven't seen
any hard data that says either Mexican sewage or runoff is that much
more contaminated than in the U.S."

The runoff affects public health in San Diego, forcing frequent beach
closures from the U.S.-Mexico border north to Imperial Beach and
Coronado. It has kept water access closed at Tijuana Slough National
Wildlife Refuge since Feb. 21.

During a two-month span last year, Mexican sewage had twice as much
nickel and lead than a similar plant in San Diego, according to records
kept by the San Diego Regional Water Quality Control Board. It had an
equal amount of silver and comparable levels of copper.

While lead and mercury can cause neurological disorders, copper, nickel
and zinc aren't harmful to human health.

Gersberg said that data makes sense. Mexican sewage is typically more
concentrated than in the United States, he said, because Mexicans use
about one-fifth the water per capita.

Metals aren't the only contaminant. Though the county monitors for
bacteria levels in the water, the real threat comes from viruses such
as Hepatitis A, Gersberg said, which can linger even once bacteria
levels return to normal.

Its presence makes water-goers more susceptible to contracting the
virus.

County agriculture officials have also found the region's greatest
concentrations of the pesticide diazinon in the Tijuana River basin,
according to data kept between 2003 and 2004. The chemical's sale was
banned by the U.S. Environmental Protection Agency in Dec. 2004, though
its use is still allowed.

Chlorpyrifos and malathion, two other widely used pesticides, are also
found in the nearby waters. None of the pesticides are a human health
risk, Gersberg said, but can pose serious risks to fish and other
aquatic life in the Pacific and nearby Tijuana Estuary.

Gersberg, whose students have studied sources of diazinon pollution,
suspects it comes from south of the border, but isn't completely sure.
County agriculture officials haven't pinpointed the pesticides'
sources, either.

"It's a matter of creating awareness of the issue," said Paul Davy,
supervising inspector in the San Diego County Agricultural Water
Quality Program. "Not that there's not awareness. But it's usually
characterized with two words -- raw sewage -- and it's much more
complex than that."

Gersberg, one of the few academics to have studied the issue in-depth,
said because contaminants come from a complex array of sources it's
hard to pinpoint where each originates -- or exactly what's in the
runoff.
 
"It's just all over," he said. "The automobile is a big contributor to
metals, be it lead or zinc. [There's] stuff in fluids and brake
linings; tires have metals in them. It all adds up."

Please contact Rob Davis directly at rob.davis@voiceofsandiego.org 
with your thoughts, ideas, personal stories or tips. Or send a letter
to the editor.