Gulf spill can't rival oil seepage from cities
Over time, tiny drips add major pollution to oceans

Jun. 30, 2010 12:00 AM
USA Today .

Human-caused spills - from everyday sources like cars, gas stations and boats - send more than 300 million gallons of oil into North American waters every decade, an amount roughly double the highest estimate of the BP spill, according to studies by the world's top scientists.

Worldwide, the numbers are even starker, according to Oil in the Sea III, a 2003 report from the National Academy of Sciences that several top scientists say remains the best estimate of oil's impact on oceans. The estimated 4 billion gallons leaking into oceans each decade from all sources is more than 25 times the highest estimates of what has spewed into the Gulf of Mexico in recent weeks.

"Wherever I am, I always go down to the beach, and I always find tar balls," said Merv Fingas, a Canadian researcher who co-wrote the study. "That was probably completely untrue even 30 years ago."

Scientists cannot compare the damage from the routine discharges into oceans and estuaries with that of the current Gulf spill because there has been so little study of the issue. The report called for additional research, but Fingas told Congress this month that little has been done to study and monitor spills.

"There is a very serious knowledge gap on discharges," Fingas said.

Another factor that has not been thoroughly studied: natural seepage of oil from under the sea. The study estimates that 493 million gallons of oil a decade enters the waters off North America, mostly in the Gulf and off California. Worldwide, an estimated 1.8 billion gallons of oil seeps out per decade.

"The amount of natural seeps is just horrendous," said James Coleman, head of Louisiana State University's Coastal Studies Institute and chairman of the 2003 study. "Every time we go down in a submarine or do a side-scan sonar, we find more."

Although massive blowouts receive the most attention, the largest human-caused source of oil into the environment is the byproduct of millions of autos and other oil-powered devices.

Oil that drips from a car's crankcase or gasoline that spills at a gas station eventually washes down gutters and storm drains and into rivers that drain into the sea, the report says. Other significant sources include recreational boating, commercial ships and tankers, and oil production.

Because government and industry do not track these spills, the totals could be much higher, the study concluded. Scientists estimate that human spills in North America could be as high as 6.3 billion gallons of oil a decade.

Alex Horne, University of California-Berkeley professor emeritus of ecological engineering, said he has frequently encountered the smell of dumped fuel or the rainbow sheen of oil while working on wetlands pollution.

"This is something that goes on year after year," Horne said. "And it's going to keep on going on. There is no end in sight to land-based spills."

Even small spills can harm the environment, according to the report and scientists. Oil products contain toxic compounds such as polycyclic-aromatic hydrocarbons that cause cancer in humans and kill marine wildlife.

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