Skip navigation Mixing oil and water again



1. Oil, oil, out of control

2. Exxon exonerated?

3. Over the long term

4. Deep oily sea

5. Memo madness translated




One part per billion of polycyclic aromatic hydrocarbon from spilled oil was harmful  to young salmon.


Well done
Before we exonerate Exxon in the Valdez spill, let's focus on the oil remaining under the rocks. "You can go to Prince William Sound and dig down in the rocky cobble beaches, and find oil as toxic as the day it was spilled," says Richard Charter, a marine conservation advocate with the non-profit Environmental Defense. (Full disclosure: the author is a member of Environmental Defense.)

A photograph shows a heavily oiled beach in 1989, adjacent to a photo of the same beach, healthy and apparently oil-free, three years later.
The 1989 picture shows pools of oil on an exposed boulder beach. In 1992, the same beach shows no oil. A combination of natural and human processes removed most of the oil by 1992. Courtesy David Page

Some studies, Charter says, show that tiny concentrations of polycyclic aromatic hydrocarbons (a group of toxic hydrocarbons ) from crude oil cause mutations in pink salmon eggs. "That means that components of oil, the fractions with the most toxicity, have mutagenic properties at levels much lower than we thought, and are much more persistent in the food chain than we ever believed possible."

In a report cited by a 2002 National Research Council book Oil in the Sea III), researchers from the Alaska Fisheries Science Center tried to sum up the effect of oil on pink salmon, the big commercial fish in Prince William Sound before the spill:

"Laboratory studies designed to emulate post-spill conditions in [Prince William Sound] verified that embryos are sensitive to long-term exposures to weathered oil in the low part per billion (ppb) range of PAH [polycyclic aromatic hydrocarbons ]. Mortalities, abnormalities, histopathological damage, and other biological effects increased with embryo exposure to ppb concentrations of PAH. ...Sensitivity of salmon embryos to weathered crude oil at ppb concentrations is unprecedented..."

Another indication that spilled oil does not just disappear comes from researchers at the Woods Hole Oceanographic Institution, who found fuel oil 30 years after a spill on Cape Cod. Woods Hole couldn't bother talking with us, but their press release said samples from 2 to 11 inches deep in the marsh "contained petroleum hydrocarbons in similar concentrations to those observed shortly after the1969 spill. ... the team found that compounds consistent with No. 2 fuel oil were still present in the sediments and may remain there indefinitely."

Making sense
Robert Spies, a scientist formerly with the Trustees Council, says the debate over pollution in Prince William Sound raises a question common to many pollution disputes: "It all comes down to who has the burden of proof. With these uncertainties, it's difficult to say with absolute certainty what's going on; unless you show every link of cause and effect in this chain, Exxon won't accept it. ...The industry hires people who believe you have to prove everything to the nth degree. They are quite often honest scientists, but I believe Exxon has the burden of proof."

Ominous-looking machinery sprays powerful jets of water onto an oiled beach.
A high-pressure, hot-water washer at work on the beaches at Prince William Sound. NOAA photo.

Still, Spies concedes that the worst effects of an oil spill are immediate, and that, "Ecosystems do rebound in the long term. Over 30 to 40 years, things are pretty much going to come back, but they will come back at different rates. Some populations take much longer than others, depending on the ability to reproduce and migrate."

From what we've read so far, the situation in Prince William Sound does not seem especially grim. A few species seem to be -- or actually are -- faltering due to the Valdez spill, or to other forces. Unless, of course, they are in a natural downswing...

Indeed, John Wiens, a scientist with the Nature Conservancy who has studied seabirds in the Sound since the spill, does not think the remaining contamination adds up to much. "The total amount of contaminated shoreline in Prince William Sound .. is a very, very small acreage. For an area like that to have impact population-wide over the sound is stretching things quite a bit."

Wiens thinks it's worth paying attention to disasters that were not made for TV. "There are a lot of studies...that suggest that the effects of low-level but chronic oil pollution are likely to be much more severe than the spectacular spills."

A particular spill, of course, is only part of the human impact on the environment. "Especially in more populated areas, these things happen over and over, and they add up to an ecological disaster," says Mundy, of the trustee council. "It's not the individual impact of one disaster, but the cumulative impact of thousands, over decades. Some are huge, but most are small, like losing a drum of gas, or a vessel losing a tank of diesel. The effects don't go away in a month or a year."

More people + more industry = more oil floating on water
At any rate, more oil will be moving across the ocean in the future, as a rising standard of living and growing population feed an overwhelming thirst for fossil fuels.

To Charter, these factors are central to the oil-spill equation. "We have been ignoring for quite a few decades the fact that oil consumption, which we take for granted in industrial societies, has an environmental cost that is paid by living resources. Things die in nature so we can get this oil. ... Somewhere, some part of the environment is being poisoned for every gallon of gasoline that arrives in a filling station."

Brown oil on blue water, with a production platform in the center, and a ship nearby.
The Ixtoc I exploratory well blew out in June, 1979, in the Bay of Campeche, Mexico. The well spilled an estimated 140 million gallons of oil, the second-largest spill in history.NOAA

And it's not just tankers that spill oil, Charter adds. The largest peacetime oil spill in history, the Ixtoc I well, spewed 140 million gallons in the Gulf of Campeche, in the southern Gulf of Mexico.

That was a shallow well. As offshore drills work in the Arctic ice, and in deeper water in the Gulf of Mexico and elsewhere, "You can create accidents you can't fix," says Charter.

Speaking of deep wells, heard about those oil slicks - er, hydrocarbon sheens?












the why files


There are 1 2 3 4 5 pages in this feature.
Bibliography | Credits | Feedback | Search

©2002, University of Wisconsin, Board of Regents.