significant risks to sensitive coastal environments. Again, these releases are concentrated in areas of petroleum production in the Gulf of Mexico and the waters off of southern California, northern Alaska, and eastern Canada. Releases from oil and gas extraction can include accidental spills of crude oil from blow outs, surface spills of crude from platforms, or slow chronic releases associated with the disposal of water produced from oil or gas-bearing formations during extraction (referred to as produced water) or oil-bearing cuttings created during the drilling process. Volatile organic compounds (VOC) commonly associated with, or dissolved in, petroleum are released during extraction activities and also contribute to the total load of hydrocarbon input to the sea. These compounds, however, rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters. Despite recent and significant decreases in the amount of petroleum released during extraction activities, the potential for a significant spill, especially in older production fields with aging infrastructures, cannot be ignored. The threat posed by even a minor spill in a sensitive area remains significant. Federal agencies, especially MMS, should continue to work with state environmental agencies and industry to enhance efforts to promote extraction techniques that minimize accidental or intentional releases of petroleum to the environment. Furthermore, like areas surrounding natural seeps, production fields represent unique opportunities to study the ecological response to slow, but chronic releases of small amounts of petroleum over time. Federal agencies, especially USGS, MMS, NSF, and NOAA, should work with industry and the academic community to develop and implement a program to understand the ecological response to such extraction-related releases as part of a larger effort to understand the impact of chronic releases from all sources of petroleum to the marine environment.

Petroleum Transportation

The transportation (including refining and distribution activities) of crude oil or refined products results in the release, on average, of an estimated 9,100 tonnes (2,700,000 gallons) of petroleum to North American waters, and 150,000 tonnes (44,000,000 gallons) worldwide, each year. Releases due to the transportation of petroleum, therefore, make up roughly 9 percent of the total petroleum input through anthropogenic activities to North American waters and less than 22 percent worldwide. Similar to releases from petroleum extraction, these volumes are dwarfed by those from other sources of petroleum to the marine environment. And like releases from extraction activities, these inputs are not trivial, as they can occur as large spills. Unlike releases associated with extraction, which tend to be concentrated in production fields in the Gulf of Mexico or coastal areas off California and Alaska, these spills can occur anywhere tanker vessels may travel or where pipelines are located statistically. Areas near major petroleum handling facilities face the greatest threat. Spills from transportation activities may release a wide variety of petroleum products (not just crude oil) each of which behaves differently in the environment (for example light distillates tend to evaporate rapidly), or contain different concentrations of toxic compounds like PAH. VOC are also released from tankers underway or involved in loading and offloading activities, and they contribute to the total load of hydrocarbons input to the sea. Again, these compounds rapidly volatilize into the atmosphere and thus appear to have a short residence time in marine waters. Despite recent and substantive decreases in the size and frequency of petroleum spills from tankers, the potential for a large spill is significant, especially in regions without stringent safety procedures and maritime inspection practices. Furthermore, tanker traffic is expected to grow over the coming decades as the centers of oil production continue to migrate towards the Middle East and Russia. Federal agencies, such as the U.S. Coast Guard and the Maritime Administration, should expand efforts to work with ship owners domestically and internationally through the International Maritime Organization, to develop and enforce effective international regulatory standards that have contributed to the decline in oil spills and operational discharges. In addition, the potential for large spills from aging pipelines and other coastal facilities is especially disconcerting, as these facilities often lie near sensitive coastal areas. Federal agencies, especially the U.S. Coast Guard, the Office of Pipeline Safety, and EPA, should continue to work with state environmental agencies and industry to evaluate the threat posed by aging pipelines and to take steps to minimize the potential for a significant spill.

Petroleum Consumption

Releases that occur during the consumption of petroleum, whether by individual car and boat owners, non-tank vessels, or runoff from increasingly paved urban areas, contribute the vast majority of petroleum introduced to the environment through human activity. On average, an estimated 84,000 tonnes (25,000,000 gallons) of petroleum are input to North American waters, and 480,000 tonnes (140,000,000 gallons) are input worldwide, each year from these diffuse sources. Therefore, releases associated with the consumption of petroleum make up nearly 70 percent of the petroleum introduced to the world’s oceans from anthropogenic sources and nearly 85 percent of the total petroleum input from anthropogenic sources to North American waters. Unlike other sources, inputs from consumption occur almost exclusively as slow, chronic releases. Furthermore, because the vast majority of the consumption of petroleum occurs on land, rivers and waste- and stormwater streams represent the most significant source of petroleum to the marine environment. Another smaller, but still

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