Richard Denison, Ph.D., is a Senior Scientist.

Now more than a month into the mammoth, out-of-control, no-end-in-sight oil spill at Deepwater Horizon, the unanswered questions, data gaps and withheld information surrounding BP’s use of dispersants are flowing in seemingly as fast as the oil is leaking.

With each passing day, it seems we know less and less about the composition and safety of these dispersants, other available dispersants, and even whether the use of dispersants– especially on this unprecedented scale – is to be advised at all.

It begs the question: Isn’t having ready answers to such questions the reason why the federal government was required to develop a contingency plan in the first place?

As I noted in an earlier post, BP has to date released more than 700,000 gallons of two dispersants, Corexit® 9527 and Corexit® 9500, that are among the least effective of the 18 dispersants that EPA has approved under the National Oil and Hazardous Substances Pollution Contingency Plan, and they appear to be among the more toxic based on limited short-term toxicity tests conducted on fish and shrimp.

Those data, plus the massive volumes involved and BP’s proposal to inject the dispersants into deep water, led EPA on May 20 to direct BP to identify and start using more effective and less toxic dispersants. BP responded over the weekend, maintaining steadfastly that Corexit® is the best choice given the circumstances.

Several impressions emerge in reading BP’s response. First, the most glaring: Big sections appear to have been redacted as confidential business information. In releasing BP’s response to its directive, EPA stated:

BP and several of the dispersant manufacturers have claimed some sections of BP’s response contain confidential business information (CBI). By law, CBI cannot be immediately made public except with the company’s permission. EPA challenged these companies to make more information public and, as a result, several portions of the letter can now be made public. EPA is currently evaluating all legal options to ensure that the remaining redacted information is released to the public. EPA continues to strongly urge these companies to voluntarily make this information public so Americans can get a full picture of the potential environmental impact of these alternative dispersants.

Whether or not it is technically legal, BP’s heavy invoking of CBI protection – in light of its dumping of what will soon exceed one million gallons of proprietary formula into the Gulf of Mexico – is deeply troubling.

It’s good to hear EPA is evaluating “all legal options” – one of which under Section 14 of the Toxic Substances Control Act (TSCA) provides that CBI “shall be disclosed if the [EPA] Administrator determines it necessary to protect health or the environment against an unreasonable risk of injury to health or the environment.”

While under this provision, EPA generally must notify a company 15 days in advance of releasing the information, there is an emergency exception: Where “the Administrator determines that the release of such data is necessary to protect against an imminent, unreasonable risk of injury to health or the environment,” only 24 hours notice is required.

In this context EPA has some nontrivial burdens to meet: “imminent” and “unreasonable” risk. But if this situation doesn’t meet those tests, what does?

Second, I can’t help but highlighting the pretty remarkable reference by BP to its substantial concern for “the potential long term effect and persistence of the chemicals in each dispersant.” Too bad that concern didn’t lead BP to demand or at least support long-term toxicity testing of Corexit®.

But BP’s concern is strong enough to lead them to point out that one of the other dispersants has a chemical in it (identity withheld) that “may degrade to a nonylphenol.” BP helpfully points out that nonylphenols “have been identified by various government agencies as potential endocrine disruptors.”

This, from a company in an industry that has done its level best to undermine researchers’ and government’s efforts to identify and act to control endocrine disruptors. Has a new leaf turned?

Finally, what is perhaps most remarkable about BP’s response, and more broadly the responses of scientists to the dispersant issue, is how little we know about what’s in these dispersants, what their effects will be on marine environments and on the workers and responders who are exposed to them – and even on the fundamental question of whether they should be being used at all to control a spill of this nature and magnitude. It appears we don’t have answers even to basic questions such as:

Do the dispersants actually work to reduce the impact of the oil?

Is it better to disperse the oil or leave it undispersed?

Is the mixture of oil and dispersant more or less toxic than the oil by itself?

See articles here, here and here for some examples of the questions scientists are raising.

Is it too much to hope, next time around, that we might have a contingency plan in place that has asked and answered such questions before something like this happens again?