A new study about the way oil from the BP Deepwater Horizon accident evaporated into the air confirms that cleanup workers were exposed to high levels of airborne pollution, and that the fumes also may have made their way onshore in Louisiana.
The study does not attempt to assess the resulting health and environmental effects.
The study’s authors also found that the way fumes from the oil combined with particles already in the air could provide a major clue to the way harmful air pollution forms from vehicle and other exhausts in urban areas.
Last June, scientists took air samples during flights over the vast area where oil was on the surface of the Gulf of Mexico.
The researchers found that 30 percent of the oil that made its way to the surface was made up of “light volatile organic carbon molecules” that evaporated within 10 hours. Another 10 to 20 percent of the surface oil was made up of heavier compounds that took several days to evaporate.
The lighter compounds combined with particles in the air and were found in a narrow plume stretching from the Macondo well northwest towards the mouth of the Mississippi River. A much wider plume of aerosols associated with the heavier compounds was found stretching across the northern edge of the oil, also moving northwest with prevailing winds towards the Louisiana coastline.
While the report does not directly address the environmental and human health effects of the aerosols, the results do indicate that offshore clean-up workers were exposed to both the vapors and the aerosol compounds, and that prevailing winds may have carried the aerosols onshore, said Joost de Gouw, lead author of the peer-reviewed report in the March 11 edition of Science magazine.
“These concentrations were high,” de Gouw said. “They are much higher than what you and I are exposed to in cities. We need to have a closer look at how these plumes of aerosol impacted people on shore.”
Some of those concerns will be addressed in future research papers by members of the same scientific team, which includes de Gouw, a research scientist with NOAA’s Earth System Research Laboratory and the Cooperative Institute for Research and Environmental Sciences in Boulder, Colo., other NOAA scientists and researchers with the University of Colorado, University of Miami, University of California-Irvine, Carnegie Mellon University and the National Center for Atmospheric Resarch.
While the study does not attempt to assess the pollutants’ health effects on workers or civilians, the differing evaporation rates support a theory that half of urban air pollution comes from organic aerosol particles from the slower-evaporating oil found in vehicle exhaust.
“Down the line, we may have to reduce emissions of these compounds to improve air quality,” said de Gouw.
In urban areas, scientists have been unable to distinguish between the aerosols formed by lighter and heavier organic compounds because they’re often also associated with heavier nitrogen oxide compounds, deGouw said.
The BP spill provided a laboratory-like setting that allowed separate reviews of the lighter compounds – which quickly attached themselves to particles in the air in the narrow plume – and the broader area of heavier compounds, which took much longer to attach to particles and form aerosols.
The federal Environmental Protection Agency in 2006 tightened its regulations of particulate matter to limit the amount of particles that are 2.5 micrometers in diameter or smaller to 35 micrograms per cubic meter of air. It would take several thousand particles of that size to fill the period at the end of this sentence.
Larger particles, sized 2.5 to 10 micrometers, are limited to 150 micrograms per cubic meter of air because they also cause fewer health problems.
When inhaled, both sizes of particles can reach deep inside of lungs, resulting in health problems, ranging from aggravated asthma to premature death in people with heart and lung disease. Particle pollution also is the main cause of visibility impairment in cities and national parks.
A podcast on this study featuring de Gouw is available on the web through CIRES at http://cires.colorado.edu/news/press/2011/gulf-air-quality.html.
An abstract of study is available on the web at www.sciencemag.org.