It's Not So Slick When Oil Ends Up in the Sea

About 29 million gallons of petroleum enters the oceans off North America each year, shows a new study by the National Research Council. The report finds that about 85 percent of that pollution can be blamed not on massive oil spills, but on the lesser amounts released by airplanes, swept into polluted rivers and from the largest culprits: recreational boats and runoff from the land.

The amount of petroleum released into North American and global waters is less than previously thought, the committee found. At the same time, however, new studies show that the environmental effects of a major oil spill are longer lasting than once thought and that even small amounts of petroleum can seriously damage marine life and ecosystems.

"Oil spills can have long lasting and devastating effects on the ocean environment, but we need to know more about damage caused by petroleum from land based sources and small watercraft since they represent most of the oil leaked by human activities," said James Coleman, chair of the committee that wrote the report.

"This doesn't mean we can ignore hazards from drilling and shipping, however," Coleman cautioned. "Although new safety standards and advances in technology reduced the amount of oil that spilled during extraction and transport in the last two decades, the potential is still there for a large spill, especially in regions with lax safety controls."

About 47 million gallons seep naturally from the seafloor into the North American oceans, more than all human sources of petroleum pollution combined. That puts North America in a better position than the world as a whole: worldwide, about 210 million gallons of petroleum enter the sea each year from human caused petroleum sources, with an additional 180 million gallons coming from natural seepage, the report says.

Of the human caused petroleum pollution entering the oceans around North America, less than eight percent comes from oil tanker or pipeline spills, says the report by the National Academies' National Research Council (NRC), titled "Oil in the Sea: Inputs, Fates, and Effects."

The report, which relies on data from a variety of sources, is said to be far more accurate than the NRC's last such assessment in 1985.

Oily Waters

Oil slicks visible from the air and birds painted black by oil get the most public attention, but it is consumers of oil -- not the ships that transport it -- who are responsible for most of what finds its way into the ocean, the NRC says.

Oil exploration and extraction are responsible for only three percent of the petroleum that enters the sea, with their effects concentrated where oil drilling rigs are at work in the Gulf of Mexico and in waters off southern California, northern Alaska, and eastern Canada.

The bulk of the 29 million gallons from humanmade sources comes from individually small source that, combined, account for about 25 million gallons of ocean petroleum pollution.

For example, oil runoff from cars and trucks is increasing in coastal areas where the population is growing and roads and parking lots are expanding. More than one half of the land based oil contamination along the North American coastline occurs between Maine and Virginia, where there are dense seaside populations, many cities, several refineries, and high energy use, the report notes.

Rivers polluted by oil in wastewater or the improper disposal of petroleum products are also a major source of oil entering the sea.

Older two stroke engines still found on many recreational boats and jet skis were purposely designed to discharge gasoline and oil. Land runoff and recreational boating account for nearly three-quarters of the petroleum released into the sea each year through human consumption.

Other sources of oil from human activities include military and commercial jets that occasionally jettison excess fuel over the ocean and ships that release oil from their engines while in port or at sea.