Fisherman Alfonzo White cast his line at Anacostia Park in the District of Columbia on an unusually warm December day.

"This is what I like to do," White said. "If I'm not working and weather permits it, I hit the water. I'd fish in a bath tub if I had to."

Perched at the end of a dock, flanked by boat ramps that are both clogged with trash and sludge, White was fishing in the Anacostia, one of the nation's most polluted urban rivers.

A railway bridge crossed the Anacostia to his right. An urban skyline crowned by RFK Stadium rose from the opposite shore. Behind him, from beyond the green swath of the riverside park, came the steady rumble of traffic on Interstate 295.

The densely developed setting, combined with past and present industry along its shores, has left the Anacostia burdened with sediment, bacteria and toxics.

Still, White is a successful and optimistic fisherman. And clearly, fish survive here. Photos on White's mobile phone show him posed with the kind of catch he hoped to land again — catfish big enough to cradle in both arms. He's pulled out plenty near this same spot.

"Like baby whales," said his wife, Linda, with a grin. "You could ride on them."

Unfortunately, the toxins that impact the river impact the fish as well. Bottom feeders like catfish, carp and eels are especially likely to absorb polynuclear aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in their tissue. Both are associated with cancer. Toxins like lead and mercury can also cause problems with the immune and nervous systems.

Now, a new study led by the Anacostia Watershed Society has raised concerns about the number of people who may be eating contaminated fish from the river.

The study, called Addressing the Risk, found that fishermen not only love to fish, they also love to share. Their catch — most often the bottom-feeding catfish — could be feeding as many as 17,000 people in the Anacostia River watershed. Some are driven by hunger.

"The biggest surprise for everybody was the extent of the sharing," said Steve Raabe, president of the private company OpinionWorks, which conducted the research. "It's percolating into the community so widely, and it's partly because of hunger. That was an eye-opener for everybody."

Government and nonprofit organizations provided funding and guidance for the research, including the EPA, National Oceanic and Atmospheric Administration, Chesapeake Bay Trust, U.S. Fish and Wildlife Service, District of Columbia, DC Environmental Health Collaborative, and Anacostia Riverkeeper.

Researchers interviewed 111 fishermen along the shoreline, who were mostly African-American and Hispanic. They also surveyed area residents about their fish consumption and conducted focus groups to explore views on sharing Anacostia fish and the health risks of eating them.

Seventy-five percent of the anglers who participated in the study said they eat or share either part or all of their catch. Of these, 35 percent do so at least once a week, and nearly half share with people beyond their own families.

This increases the likelihood that contaminated fish are reaching children and women of child-bearing age.

Dr. Janet Phoenix of the DC Environmental Health Collaborative said that her group lists toxics among their top three concerns for District residents. "I was glad to see the intersection of a water study that also looked at human health. I certainly see people fishing along the Anacostia but I was surprised at the extent to which the anglers are sharing their catch with others," Phoenix said. "It's pretty staggering."

The U.S. Fish and Wildlife Service recently found that 50–68 percent of the river's brown bullhead catfish had liver tumors. Ten to 23 percent had skin tumors. But while anglers often inspect their fish for visible sores or lesions, they are less likely to know that a fine-looking fish can carry cancer-causing contaminants in its tissues.

"Fishermen tend to be focused on the appearance of the fish," said Fred Pinkney of the U.S. Fish and Wildlife Service. "If it has a lot of sores, they throw it back. But you can have plenty of PCBs in a catfish that looks absolutely beautiful."

Both Maryland and the District of Columbia warn anglers to avoid eating catfish, carp and eel from the Anacostia and to limit their servings of largemouth bass, sunfish or other fish.

But the new study shows that some people aren't aware of the health risks associated with eating fish from the Anacostia River. Approximately 22 percent of the fishermen interviewed were not aware of the warnings. That number rose to 53 percent among Spanish-speaking fishermen and 44 percent among general residents of the Anacostia watershed.

Many are aware of the risk, but eat — and share — the fish anyway.

"Even if a person knows about the risk, they are still hungry today," said Dottie Yunger, a river advocate and director of the faith-based group Chesapeake Covenant Communities. "What can we say to a person who is hungry right now — that you might get cancer 20 or 30 years down the road?"

Fishermen also feel good knowing that they provide fish for people who truly need the meal. They are often approached by people along the riverbank, who ask for fish that would otherwise be thrown back. One man commented, "You feel bad if you throw all of them back and then they ask you if you've caught anything. Then the next thing you know they may not have anything to eat."

The study suggests that more people might heed the warnings if the message was delivered with more pictures, less text and in multiple languages. Additional outreach through churches and informal fishing groups might be helpful, too.

Complicated health advisories were a turn-off, and sample messages only drew a strong reaction from fishermen when they used the word "cancer." But such signs won't appear anytime soon.

Bryan King is the associate director of fisheries and wildlife for the District Department of the Environment. He said that it's difficult, if not impossible, to scientifically link fish to a specific case of cancer when a person's environment also includes toxins from highways, power plants and other sources.

Without data directly linking fish exposures to cancer in humans, they can't print such a warning on their signs.

"The District, like many other places, is faced with a daunting task. How do we promote recreational angling while decreasing the consumption of contaminated fish?" King said. "We want to inspire a value, not scare people away from the water."

Julie Lawson, communications manager for the Anacostia Watershed Society, said that no one wants or expects fishing on the river to stop. Sharing will continue, too. But asking anglers to steer clear of higher risk species, like catfish, is important for stemming the immediate health risk.

In the long run, the sponsors of the study want more people engaged with cleaning up the river.

"We want to get the message out to all of these fishermen that they should be able to fish in their river and eat what they catch," Lawson said. "It's an environmental justice issue, that they should be able to fish in their river and feed their families and neighbors with dignity and safety."

In other words, Lawson is hoping that this new report will make more people mad. Their energy will be needed to sustain the large amounts of time and resources that will be needed to address the toxic problems on the Anacostia River and in the fish that people consume.

Advocates are encouraged by the work that is under way, like the cleanup of some toxic "hot spots" and an intense study by the District of Columbia that could position the entire tidal portion of the river to be treated as a Superfund site.

In the meantime, Alfonzo White planned to wrap up his day on the river as he usually does — by taking fish home to share with his neighbors.