On this, the 50th day since the oil spill began in the Gulf of Mexico, Coast Guard Admiral Thad Allen said that the federal government has been aggressive with its response, but acknowledged room for improvement.

In an interview with ABC's Diane Sawyer, Allen shared the difficulties the government still faces as it copes with a disaster that has already put millions of gallons of oil into the Gulf of Mexico and soiled hundreds of miles of coastline.

Play

"We need to flatten and streamline this and cut the cycle time from when oil is sighted until we get a response team on it," Allen said.

A flow chart detailing the National Incident Commander's support organization gave some indication today of the bureaucracy that's already involved in the cleanup effort.

The chart shows 13 agencies involved in the response effort, as well as three sub-departments, including the Minerals Management Service (MMS) and the National Oceanographic and Atmospheric Administration (NOAA). The chart, dated June 6, shows a maze of responsibility, all leading back to Adm. Allen himself.

"It's not easy to go from town to to town and see the level of frustration and the anger of the American people out there," Allen said. "I worked on the water all my life. [...] And I completely empathize with the folks down there having such a hard time. That's the reason it's very critical that we bring unity of effort to this entire thing."

Play

When pressed about why boats remain docked along the coast, unused in the cleanup effort, Allen defended the government's actions.

"Diane, we qualified over 2,600 vessels of opportunity and in the last couple of days, for example, in Alabama, we've deployed over five or six hundred. It's a matter of reconciling the type of boat, the operator competency, getting them trained and reconciling them with the equipment. We're actively doing that," he said.

50 Days In, Flow Rate Still Unknown

BP and the government said they were able to collect some 620,000 gallons of oil on Monday using the containment cap device, up from a 460,000 gallons on Sunday.

Play

Though authorities say that they're now collecting anywhere from a third to three quarters of the oil that is coming out of the damaged well, no one can truly be sure because a precise measurement of the flow rate is still unavailable.

When asked today whether the flow could be as high as 60,000 barrels per day, Allen said he simply didn't know.

"Everything we know and everything we see is through either the remote sensors or remote-operated vehicles that are like looking through a particular keyhole at a particular time," Allen told Sawyer.

A Coast Guard team has been assigned to nail down the rate of the leak. Underwater video shows inky oil still billowing out of the damaged well.

Play

Government Admits to Undersea Oil Plumes

For the first time today, the federal government acknowledged that some of the oil that has already gushed into the ocean has not risen to surface but instead remains deep below in huge, undersea plumes.

Scientists have been warning of the plumes since mid-May, but thus far, both BP and federal officials had denied their existence.

"There aren't any plumes," BP CEO Tony Hayward said on May 30, echoing his company's suggestion that the oil would rise to the surface.

And back on May 17, NOAA dismissed university researchers' claims about plumes as "misleading, premature and, in some cases, inaccurate."

Play

Today, NOAA acknowledged a different reality.

"NOAA is confirming the presence of very low concentrations of subsurface oil," said administrator Jane Lubchenco. "The bottom line is yes, there is oil in the water column.

Tests confirm that oil collected from undersea plumes 40 nautical miles northeast of the site of the Deepwater Horizon accident has the same oil "fingerprint" as that which is gushing out of the well. Even in low concentrations, oily water threatens marine animals by depleting the ocean's oxygen content.

But despite weeks of warning about the threat of oily plumes, government authorities didn't seem to be prepared to deal with a crude problem that can't be skimmed off the surface.

"We have not generally done subsurface responses," Adm. Allen told a news conference today. "In my own personal experience, I have not dealt with it."

Play

BP Encounters Criticism Over Claims

As for BP, the company announced today that it will donate net revenue from the oil recovered from the spill to help fund wildlife recovery efforts. At current recovery rates, that would amount to about $1.1 million per day.

The company has also promised to pay all "legitimate claims" related to the spill.

Today, Alabama Gov. Bob Riley called on the National Guardsmen to help spread the word that the condo owners, fishing captains and others are all eligible to apply for compensation from BP, Adm. Allen said

The company says it has already spent $49 million on claims, but across the Gulf, tens of thousands of workers and business owners whose livelihoods have been affected by the accident say they're now running out of money, waiting for checks from BP.

On top of that, many are now learning that payments for lost revenue will not be based on what would have been a big season this year -- they'll be based instead on the last three years.

For many fishermen and other Gulf Coast workers, they had been awful years, with paychecks battered by the effects of Hurricane Katrina.

Why?

"Well, we have to start somewhere," a BP spokesperson told ABC News today.

BP says that 90 percent of claims paid so far have gone to individual workers, the rest to businesses. Business owners say they've been required to turn over a mountain of paperwork, keeping track of taxes, receipts and other records.

Boat welder Bill Farmer says he has already lost $45,000 in business, but he and others refuse to let BP get away by paying a tiny claim.

"They have the same fears I have. What if we settle for a little bit and this impacts us for the next five years?" Farmer said.

Hayward to Appear Before Congress

BP also said that CEO Tony Hayward will appear before a congressional subcommittee on June 17 to testify about his company's role in the spill, where he's sure to face pointed questions and criticism.

Today on Capitol Hill, a brother of a man killed in the Deepwater Horizon explosion already had a message for Hayward.

"I want to take the opportunity to address recent remarks made by Tony Hayward, CEO of BP," said Christopher Jones, the brother of Gordon Jones. "In particular, he publicly stated he wants his life back. Well, Mr. Hayward, I want my brother's life back."

Click here to return to the 'World News' page.

ABC's Dan Arnall and the Associated Press contributed to this report.

Dozens in Louisiana have been hospitalized with health problems blamed on airborne toxic chemicals in the air a month after oil began to flood the Gulf of Mexico from a broken BP pipeline.

Those exposed to the growing oil spill include residents, cleanup workers and those providing relief aid. Thus far, 71 have been hospitalized due to oil spill related health problems, according to the Louisiana state health department. And while some say chemicals in the oil itself are to blame, others speculate chemicals called dispersants being used to break up the massive slick could be playing a role.

Play

One local fisherman was evacuated by helicopter to West Jefferson Medical Center in New Orleans from his boat after he reported feeling dizzy.

"I was feeling weak and I had high blood pressure," the fisherman, who did not want to be identified, told West Jefferson Medical employees in an interview videotaped by the hospital. "We thought it was maybe from the dispersant. We had other guys too that was feeling bad. He had aches and nauseated."

Doctors at West Jefferson Medical Center concluded the fisherman's symptoms suggested he was exposed to some kind of irritant and exposure. However, according to Dr. Robert Chugden, medical director for emergency services at West Jefferson Medical Center, it is difficult to tell whether the oil spill is in fact the culprit for many patients' symptoms.

Play

"In all honesty they're working in a hot, muggy, high-humidity environment, so that alone can bring on these symptoms," said Chugden. "It's very hard to say what's going on. But having petroleum fumes surrounding you is not pleasant."

Many Factors of Oil Spill are Dangerous, Experts Say

Federal agencies including the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH), a division of the CDC, also report that many relief workers responding to the oil spill have been exposed to dangerous levels of airborne toxins.

Many experts say oil can do harm both through direct contact and airborne exposure to the chemicals. Many studies suggest that short-term exposure to oil can be linked to nausea, headache, dizziness, and eye and throat irritation, as well as both upper and lower respiratory tract symptoms.

When crude oil is exposed to air, it can turn into thick, sticky tar balls. Some people who come in contact with them may have allergic reactions to the chemicals. But in general, Chugden said, the thicker the oil, the less toxic it is.

However, according to Dr. Michael Harbut, director of the environmental cancer program at Wayne State University in Detroit, tar balls, though not as dangerous, may signal the presence of crude oil.

"While it's still pumping, you don't have any idea if you're looking at an isolated tarball, or a harbinger of more serious consequence," said Harbut. "Where there's a tar ball, there's a crude oil concentration not far behind."

Besides the danger of inhaling fumes emitted by oil, planned burning of petroleum can also be a health hazard, according to the National Oceanographic and Atmospheric Administration. NOAA says tiny particles in the smoke can drift into the air downwind of the burn, and these particles can irritate the lungs of people with asthma and other lung diseases. Pregnant women, children and the very old can also be sensitive.

"The people that we see are reporting there's petroleum odor in the air, and it causes irritation or a sore throat," said Chugden. "We have not honestly seen serious pulmonary damage. All we've seen so far are symptomatic."

Health Risks of Dispersants Minimal, Experts say

Dispersants, chemicals that are sprayed onto oil slicks to speed the process of natural dispersion, are also thought by many to be potentially harmful. Dispersants are used to remove large amounts of certain oil types from the sea surface by breaking up the oil so that it is diluted in the water.

But not much is known about the long term risks of dispersants, since it is not used often, said Ronald Tjeerdeema, chair of the department of Environmental Toxicology at University of California, Davis. In general, Tjeerdeema said, dispersants pose a minimal health risk to the public, and may reduce the health risk associated with crude oil.

"When you disperse oil, you reduce the amount of volatile chemicals coming off the water from the oil and from the dispersant," said Tjeerdeema.

While not much is known about the health effects of exposure to dispersants or when dispersant chemicals are combined with the oil it is designed to break up, direct contact with crude oil, chemical inhalation, and possible air exposure to dispersants can be a fatal combination, Harbut said.

"You have the use of products which have not had their ingredients identified to the people they're getting sprayed on," said Harbut. "You have a known category of carcinogens -- petroleum distillates in the dispersant and carcinogens in the crude oil."

Although Gulf shores are popular for their beaches, area health departments advised beachgoers against swimming. Gulf states including Mississippi and Florida have recommended that residents stay out of water where they are able to see or smell oil. Alabama and Louisiana have issued swimming advisories, discouraging people from swimming in gulf waters, according to their respective state health departments.

However, according to Chugden, the real danger for many Gulf residents may extend beyond contact with oil in the water.

"Our concern is we're in hurricane season and it's going to aerosolize everything in the water," said Chugden. "And there will be micodroplets that everyone is going to inhale."

Long Term Health Implications

While there is some preliminary evidence suggesting that oil may contribute to chronic conditions, there are no long-term studies looking at the impact of oil exposure. Still, many experts suggest that while minor symptoms have been attributed to the oil spill so far, the future may hold more serious health problems.

"In the long haul, there is a significant worry in terms of the development of chronic conditions -- chronic asthma, chronic lung, and in some cases cancer," said Harbut. "I will not be surprised to see an increase in cancer."

NIOSH is conducting a voluntary survey to evaluate oil spill response workers' safety training, expected exposure, and use of personal protective equipment, the agency told ABC News. The agency also plans to track the health effects of the oil spill on response workers over time.

According to Chugden, even with low levels of exposure, over years, toxicity can build up in tissues such as the kidney and lungs.

"I think we haven't had enough time to understand health impacts of the spill here yet," said Chugden. "I think it's certainly too early to tell this spill's full health impact."