Offshore Oil Pollution Comes Mostly as Runoff, Study Says
By ANDREW C. REVKIN, New York Times, May 24, 2002
Most oil pollution in North American coastal waters comes not from leaking tankers or oil rigs, but
rather from countless oil-streaked streets, sputtering lawn mowers and other dispersed sources on
land, and so will be hard to prevent, a panel convened by the National Academy of Sciences says in a
The thousands of tiny releases, carried by streams and storm drains to the sea, are estimated to equal
an Exxon Valdez spill - 10.9 million gallons of petroleum - every eight months, the report says.
When fuel use on water, either inland or offshore, is also taken into account, the report says, about
85 percent of the 29 million gallons of marine oil pollution in North America each year comes from
users ‹ drivers, businesses, boaters ‹ and not from the oil industry. In particular, spills from
tankers, barges and other oil transport vessels totaled less than a quarter-million gallons in 1999,
down from more than six million in 1990.
The shift follows a substantial tightening of environmental regulations on oil exploration and
shipping since the grounding of the Exxon Valdez in 1989. The new report is the academy's third
examination of marine oil pollution since 1975, but the first since the Exxon Valdez spill.
More than half the oil runoff in North America occurs along the East Coast from Virginia to Maine, the
report said. That concentration of oil pollution, the authors said, reflects the density of people,
vehicles and other sources in the corridor from Washington to Boston.
Oil carried in runoff is particularly damaging, the report said, because it typically ends up
discharged by rivers and streams into bays and estuaries that "are often some of the most sensitive
ecological areas along the coast." That relentless runoff carries traces of a host of chemicals that
are found in most fuels and that can harm marine life even in low concentrations.
"We've all seen the sheen on the streets," said one author, Dr. Nancy N. Rabalais, a marine biology
professor at the Louisiana Universities Marine Consortium. "That eventually is going to run off and
end up in a river. The cumulative effect of human activity all over the landscape eventually gets into
Worldwide, the panel estimated, 70 percent of marine oil pollution comes from fuel users, not
producers or shippers.
The panel said one significant source of oil pollution, though a much smaller one than fuel use on
land, was the two-cycle engines still used in many outboard boats and personal watercraft like Jet
Skis. Those engines use a small amount of unburned fuel as lubricant and then expel it. The report
encouraged the Environmental Protection Agency to continue to promote a shift to different engine
designs, and groups representing the watercraft industry said yesterday the move was under way.
The academy's findings echo a growing consensus in recent years that "nonpoint" pollution, from
countless dispersed sources, poses one of the nation's most serious and intractable environmental
problems. With tankers or oil fields, specific agencies can require double hulls or dikes to hold back
leaks, but no agency polices parking-lot runoff.
"There are lots of good regulations in the Clean Water Act that deal with point discharges, and we
have the Coast Guard to deal with oil spills," Dr. Rabalais said. "But no matter whether it's
pesticides, fertilizers, oil or grease, we're not to the point of managing these things. And they are
The study, by 14 scientists and engineers, including some from the oil industry, was produced by the
National Research Council, the branch of the National Academy of Sciences that conducts independent
studies for the government.
While emphasizing the problem of oil pollution in runoff, the report noted a sharp drop in the number
and volume of accidental spills by tankers and barges in American waters since the Valdez grounding.
Even with that improved record, the report said, it is important for governments to continue
intensifying safeguards against such accidents, because the transporting of oil around the world will
But it is just as important to start focusing on ways to better measure oil releases destined for
waterways and to pinpoint their sources, the report said.
William D. Hickman, a spokesman for the American Petroleum Institute, a trade group in Washington,
said the report correctly highlighted both progress in the oil industry and continuing pollution
The report also said more work should be done to understand the effect of oil seeping naturally from
underwater deposits in the ocean. Humans release about 210 million gallons of petroleum a year into
the seas, the report said, while natural seepage adds 180 million gallons.