A federally convened group of scientists is set to recommend that BP BP -0.37% BP PLC ADS U.S.: NYSE $51.61 -0.19 -0.37% July 11, 2014 4:00 pm Volume (Delayed 15m) : 1.94M AFTER HOURS $51.64 +0.03 +0.06% July 11, 2014 5:33 pm Volume (Delayed 15m): 62,520 P/E Ratio 15.72 Market Cap $158.93 Billion Dividend Yield 4.53% Rev. per Employee $4,553,210 06/08/14 Plaintiffs' Lawyers Take Aim a... 05/23/14 Mexico's Energy Minister Under... 04/22/14 BP to Sell Interests in Four A... More quote details and news » PLC and the government continue spraying chemicals into the Gulf of Mexico to help prevent leaking oil from washing ashore, even though the scientists have serious concerns about the potential long-term damage to sea life.

The group's report, due this week, comes after BP's latest efforts to plug the leaking Deepwater Horizon oil well failed. If further interim measures to cap the well don't work, large additional amounts of the chemicals, known as "dispersants," could be sprayed into the Gulf until relief wells can be completed and the gusher capped, which could take until late summer.

Coast Guard Ensign Adam Mosely logs sample data from Gulf water. US Coast Guard

Research ships sponsored by the Obama administration and universities have recently found what scientists believe is evidence that clouds of tiny oil droplets are collecting deep underwater.

Tests are under way to determine whether the droplets are oil—and, if so, whether they were caused by the dispersants. Scientists suspect those droplets could harm fish, birds and sea mammals in coming months and years.

But scientists say they can't make firm predictions about the effects of chronic exposure, in part because dispersants have rarely been used for long periods of time. In addition, funding for research on dispersants has lagged in recent years as concern about oil spills slipped off the political agenda.

"The bottom line is that there hasn't been political will to fund this, because we haven't had a spill," said Nancy Kinner, co-director of an oil-spill-response institute at the University of New Hampshire.

When the Gulf spill began in April, her institute—the Coastal Response Research Center, created in 2003 with funding from the National Oceanic and Atmospheric Administration—hadn't received any new federal funding for oil-spill research since 2007.

Last week, with only a few days' notice, the government paid Ms. Kinner's institute to hold a large meeting on dispersant use in Louisiana. The report from the closed-door meeting will recommend that dispersants continue to be sprayed on the gulf as a "tradeoff" to prevent massive amounts of oil from washing into coastal marshes, she said. The report also will call on the federal government to continue to do environmental testing to monitor whether that tradeoff remains worthwhile.

"We are assuming that keeping it out in the water column is better than letting it into the coastal areas," Ms. Kinner said of the leaking oil. Louisiana's marshes are crucial to many species—including to shrimp, a major industry in the state.

Ms. Kinner, other scientists and top administration officials say the tradeoff makes them increasingly uneasy.

Last month, the Environmental Protection Agency ordered BP to find a less-toxic alternative to the dispersant it has been using most, Corexit 9500, or explain why it couldn't find one.

But Nalco Co., Corexit's maker, says the dispersant is safe. And when BP told the EPA that it could find no less-toxic dispersant in the quantities necessary to fight this spill, the EPA relented. The agency asked BP to reduce the amount of Corexit 9500 the company is using.

EPA Administrator Lisa Jackson said in testimony to a House subcommittee Thursday that the administration has requested an additional $2 million for research into the environmental and health effects of the spill, including the use of dispersants. The government's "modest investment" in dispersant research thus far, she said, "must increase to address the uncertainties that have arisen" from the spill.

The ongoing leak from the well on the ocean floor raises two main concerns in the Gulf: the effect of dispersed oil particles and the effect of the chemical dispersants themselves. Particularly unclear is how sea life will fare when exposed to dispersed oil over long periods of time. Past studies have looked at how short-term exposure could kill fish and sea mammals.

The long-term question didn't get much consideration before April 20, when the Deepwater Horizon drilling rig exploded and unleashed the torrent of oil that has been spewing into the Gulf ever since. Based on government estimates released last week, the well is pouring out 12,000 to 19,000 barrels of oil every day. That would make the Gulf spill bigger than the 1989 Exxon Valdez disaster.

The EPA doesn't regulate dispersants' toxicity. It requires dispersant manufacturers to test the amount of dispersant necessary to kill a given quantity of one type of fish and one type of shrimp in lab tests. But it doesn't impose any maximum toxicity level that dispersants must stay below.

The EPA does require dispersant manufacturers to show that their chemicals break apart and sink a given amount of oil in a given time in a lab test. The dispersants that have that documentation are placed on a list maintained by the EPA, along with the dispersants' toxicity levels.

Because only small amounts of dispersant were used in the past, "the toxicity of a dispersant has not historically been a driving consideration," said Chris Piehler, director of the clean-waters project for the Louisiana Department of Environmental Quality and one of the Louisiana officials involved in the current oil-spill response.

BP and the federal government said they have applied more than 900,000 gallons of dispersant onto the oil so far, an unprecedented amount.

The EPA's Ms. Jackson said she hoped the quantities of dispersant could be reduced as much as 75% from initial levels, and federal officials say the amount of dispersant being applied to the spill is down. But even at those reduced quantities, there will still be a lot of dispersant in the Gulf.

Write to Jeffrey Ball at jeffrey.ball@wsj.com