Lawn chemicals Add to Delta Poisoning

Toxicity study called most comprehensive ever

By Audrey Cooper

Record Staff Writer

The grass may be greener next door, but pesticides used on those manicured lawns have poisoned Stockton's waterways, according to a six-year study released Thursday.

Agricultural, residential and commercial pesticide applications wash into local streams via stormwater drains during rain storms. At those times, pesticides levels are high enough to kill zooplankton, according to the study.

Zooplankton is a microscopic animal at the core of the food chain.

The study was a joint effort of independent analysts, the Central Valley Regional Water Quality Control Board and local antipollution group DeltaKeeper.

The study began with data from 1994 and included about 160 toxicity tests. It is the most comprehensive study of its kind ever done in the United States, said G. Fred Lee, who analyzed the data and wrote the study.

"It's not just Stockton with this problem. The problem is that we do not adequately evaluate the potential for pesticides to be carried off properties," Lee said.

The two pesticides named in the study—diazinon and chlorpyrifos—are popular ant-termite and termite-control products. Millions of pounds of those chemicals are used in the United States each year, Lee said.

Because of a government-ordered phase-out, diazinon will be unavailable for residential use by 2005. Chlorpyrifos is scheduled to be taken off the shelves at the end of the month. They still will be available to farmers.

Experts worry the next generation of pesticides will be even better at their intended purpose: killing animals and plants. Some newer pesticides are also difficult to monitor.

"The water is already bad and as we shift to more and more toxic chemicals, it's likely to get worse," said DeltaKeeper head Bill Jennings. His group took over the water monitoring for the study in 1996 at the request of the regional water board.

Data in the study shows that some urban streams have pesticide levels up to 24 times higher than state limits. Those sort of alarming statistics lead to Stockton's streams being listed as some of the state's most pesticide-polluted waterways.

Five waterways were tested during the six years of the study: Mosher Slough, Five Mile Slough, the Calaveras River, Walker Slough-Duck Creek and Smith Canal. Smith Canal and Five Mile Slough receive stormwater runoff only from Stockton, indicating a problem with residential and commercial pesticide use. Stormwater that flows into the other three waterways also includes agricultural runoff.

The study isn't good news for Stockton officials, who are awaiting to hear next month what new rules the regional board wants in place to decrease stormwater pollution in the city.

The city could eventually be forced to use pesticide-free methods to maintain parks, conduct more education campaigns, and install treatment systems on the end of major storm drain outfalls, said Philip Isorena, who works on San Joaquin County stormwater issues for the regional board.

All of that costs money.

The city will also have to study where the pesticide runoff is coming from, Isorena said.

Meanwhile, residents and businesses can start using alternative pest-control methods, said Stockton's stormwater-outreach coordinator, Susan Mora Loyko.

Mulching yard waste is one of the best replacements for fertilizers, she said. Also, residents should read the labels on their pesticides and only apply the directed amount.

"You can also use oyster shells or barbecue ash in plants to deter snails and slugs and avoid spraying the methylethyl badstuff," she said.

Spraying soapy water or glass cleaner along ant trails could confuse the critters and keep them from coming back.

* To reach reporter Audrey Cooper, phone 546-8298 or e-mail acooper@recordnet.com