Jump to main content or area navigation.

EPA Response to BP Spill in the Gulf of Mexico

BP's Analysis of Subsurface Dispersant Use

In response to the BP oil spill, EPA monitored air, water, sediment, and waste generated by the cleanup operations. Ongoing response and restoration efforts are posted to RestoreTheGulf.gov.

While emergency response data collection has ended, results continue to be available on this site. Any new data will continue to be posted to this site, and data will continue to be available here for the foreseeable future.

Much of the content of this site continues to be available for historical and information purposes, but we are no longer updating these pages on a regular basis.

More information about dispersant use on the BP spill

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Dispersant-Related Data

EPA and the US Coast Guard’s directive requires BP to implement a monitoring and assessment plan for subsurface and surface applications of dispersants as part of the BP oil spill response. The directive also requires BP to include a more thorough oil analysis which will allow EPA to determine whether the plume is toxic to aquatic life.

EPA evaluation criteria for determining whether application of subsea dispersants should be shut down include:

  1. A significant reduction of dissolved oxygen. Dissolved oxygen analysis measures the amount of gaseous oxygen dissolved in the water. Adequate dissolved oxygen is necessary for good water quality. A reduction in dissolved oxygen from background levels to below 2 mg/L is considered significant. Learn more about dissolved oxygen.
  2. The results of rotifer toxicity tests. These are standardized tests that evaluate the potential toxicity of the water. Rotifers are sensitive small invertebrates that occur in the Gulf of Mexico and are important to the food chain. Toxicity is determined by comparing the survival of the rotifers exposed to the deep water samples to survival in clean water. A concentration of dispersant that is lethal to 50% of exposed rotifers (commonly called the LC50 value) is considered significant. Learn more about rotifer toxicity testing.
  3. The evaluation of the conditions above in addition to other factors including shoreline, surface water, and other human health and ecological impacts.
Here are the BP sampling results (in various formats) from May 15 to August 31 (updated files posted September 3, 2010)
(includes dissolved oxygen, toxicity and analysis for total petroleum hydrocarbons):

Dissolved oxygen measurement methods aboard the RV Brooks McCall May 2010 (PDF) (10pp, 245K)

EPA is working closely with its federal partners, including the U.S. Coast Guard and NOAA, to ensure an aggressive dispersant monitoring plan is implemented by BP and that data are regularly and rigorously reviewed.

To-date, the toxicity data does not indicate any significant effects on aquatic life. Moreover, decreased size of the oil droplets is a good indication that, so far, the dispersant is effective.

EPA is closely watching the dissolved oxygen levels, which so far remain in the normal range. Dissolved oxygen levels initially appeared low when measured with a device called a LaMotte tool. In order to conduct a more thorough analysis, more sensitive equipment was then employed, called an Extech Probe. The subsequent dissolved oxygen readings from the Extech Probe indicate that dissolved oxygen levels are within the normal range.

Daily Reports: Tracking the Plume of Dispersed Oil using Particle Size Distribution Measurements   Sampling Location Maps
August 10 (PDF) (2pp, 82K)    
August 9 (PDF) (3pp, 126K)    
August 8 (PDF) (3pp, 161K)    
August 7 (PDF) (1pp, 73K)    
August 6 (PDF) (3pp, 88K)    
August 5 (PDF) (2pp, 84K)    
August 4 (PDF) (2pp, 54K)    
August 2 (PDF) (3pp, 120K)    
August 1 (PDF) (2pp, 112K)    
July 31 (PDF) (3pp, 55K)    
July 30 (PDF) (2pp, 54K)    
July 29 (PDF) (2pp, 54K)    
July 28 (PDF) (4pp, 96K)    
July 27 (PDF) (3pp, 95K)    
July 22 (PDF) (3pp, 121K)    
July 21 (PDF) (3pp, 124K)    
July 20 (PDF) (4pp, 122K)    
July 19 (PDF) (3pp, 647K)    
July 18 (PDF) (2pp, 680K)    
July 17 (PDF) (3pp, 613K)    
July 16 (PDF) (3pp, 86K)    
July 15 (PDF) (2pp, 111K)    
July 14 (PDF) (3pp, 124K)    
July 12 (PDF) (2pp, 148K)    
July 11 (PDF) (3pp, 158K)    
July 10 (PDF) (3pp, 102K)    
July 9 (PDF) (3pp, 128K)    
July 6 (PDF) (2pp, 138K)    
July 5 (PDF) (2pp, 112K)    
July 4 (PDF) (3pp, 94K)    
July 3 (PDF) (2pp, 87K)    
June 28 (PDF) (2pp, 183K)    
June 27 (PDF) (2pp, 239K)    
June 26 (PDF) (3pp, 288K)    
June 25 (PDF) (3pp, 122K)    
June 24 (PDF) (2pp, 117K)    
June 23 (PDF) (2pp, 113K)    
June 22 (PDF) (1pg, 79K)    
June 19 (PDF) (3pp, 415K)    
June 18 (PDF) (2pp, 342K)    
June 17 (PDF) (3pp, 332K)    
June 16 (PDF) (3pp, 242K)    
June 15 (PDF) (4pp, 279K)    
June 14 (PDF) (4pp, 282K)    
June 13 (PDF) (3pp, 436K)   June 11 - 13 (JPG) (73K)
June 12 (PDF) (2pp, 339K)  
June 11 (PDF) (3pp, 407K)  
June 10 (PDF) (4pp, 133K)    
June 9 (PDF) (4pp, 129K)    
June 8 (PDF) (4pp, 134K)    
June 7 (PDF) (2pp, 356K)   June 5 - 7 (JPG) (82K)
June 6 (PDF) (3pp, 464K)  
June 5 (PDF) (3pp, 357K)  
June 4 (PDF) (5pp, 1.32 MB)    
June 3 (PDF) (3pp, 127K)    
June 2 (PDF) (4pp, 270K)    
June 1 (PDF) (4pp, 474K)   June 1 (JPG) (89K)
May 30 (PDF) (3pp, 210K)   May 30 (JPG) (89K)
May 29 (PDF) (5pp, 299K)   May 29 (JPG) (120K)
May 28 (PDF) (1pg, 151K)   May 28 (JPG) (114K)
May 27 (PDF) (3pp, 160K)    
May 25 (PDF) (3pp, 302K)   May 25 (PDF) (1pg, 62K)
May 24 (PDF) (3pp, 314K)   May 24 (PDF) (1pg, 62K)
May 23 (PDF) (3pp, 242K)   May 23 (PDF) (1pg, 62K)
May 21 (PDF) (3pp, 299K)   May 21 (PDF) (1pg, 62K)
May 20 (PDF) (3pp, 277K)   May 20 (PDF) (1pg, 62K)
May 19 (PDF) (3pp, 113K)   May 19 (PDF) (1pg, 62K)
May 17 (PDF) (3pp, 26K)   May 17 (PDF) (1pg, 87K)

Top of page

More information about dispersant use on the BP spill

Connect with us:
Facebook: EPA
Twitter: EPA
Photos: BP Spill | more photos
Get email updates

Jump to main content.