Modeled Air Pollution from In SituBurning and Flaring of Oil and Gas Released Following the Deepwater HorizonDisaster

The GuLF STUDY, initiated by the National Institute of Environmental Health Sciences, is investigating the health effects among workers involved in the oil spill response and clean-up (OSRC) after the Deepwater Horizon(DWH) explosion in April 2010 in the Gulf of Mexico. Clean-up included in situburning of oil on the water surface and flaring of gas and oil captured near the seabed and brought to the surface. We estimated emissions of PM2.5and related pollutants resulting from these activities, as well as from engines of vessels working on the OSRC. PM2.5emissions ranged from 30 to 1.33e6kg per day and were generally uniform over time for the flares but highly episodic for the in situburns. Hourly emissions from each source on every burn/flare day were used as inputs to the AERMOD model to develop average and maximum concentrations for 1-, 12-, and 24-h time periods. The highest predicted 24-h average concentrations sometimes exceeded 5000 µg m−3in the first 500 m downwind of flaring and reached 71 µg m−3within a kilometer of some in situburns. Beyond 40 km from the DWHsite, plumes appeared to be well mixed, and the predicted 24-h average concentrations from the flares and in situburns were similar, usually below 10 µg m−3. Structured averaging of model output gave potential PM2.5exposure estimates for OSRC workers located in various areas across the Gulf. Workers located nearest the wellhead (hot zone/source workers) were estimated to have a potential maximum 12-h exposure of 97 µg m−3over the 2-month flaring period. The potential maximum 12-h exposure for workers who participated in in situburns was estimated at 10 µg m−3over the ~3-month burn period. The results suggest that burning of oil and gas during the DWHclean-up may have resulted in PM2.5concentrations substantially above the U.S. National Ambient Air Quality Standard for PM2.5(24-h average = 35 µg m−3). These results are being used to investigate possible adverse health effects in the GuLF STUDY epidemiologic analysis of PM2.5exposures.