Buenos Aires - The picturesque La Boca district draws hordes of tourists to stroll its narrow streets lined with colourful buildings and eat at outdoor restaurants. Now it has a new, unwanted claim to fame: The Riachuelo River that flows through the neighbourhood has been named one of the planet's 10 dirtiest places.Thousands of people live along the river, and environmentalists say a court-ordered cleanup of decades of industrial pollution and sewage has made little progress in five years. Many residents still need to be relocated under the court ruling, and toxic substances are still emptying into the Riachuelo.On a recent day, tourists ambled along the Caminito walkway full of souvenir shops and cafes amid the funk emanating from the river about 700 feet away. Although the odour of the brown-gray river can be overpowering some days, the historic district, which is known as a tango hotspot and home of the popular soccer team Boca Juniors, remains one of Buenos Aires' top tourist draws."I smell it from my home, just a few blocks away, and I often have to keep the windows closed," said Edgardo Gomez. "When are they going to finish this cleanup plan?"Many are asking the same question. About 3.5 million people live in the southern districts of Buenos Aires and the 14 nearby municipalities as the river flows some 60km from Buenos Aires province to just south of the capital.Heavy metals and acidA report by the environmental activist groups Blacksmith Institute and Green Cross of Switzerland stirred up Argentines by ranking the river as the eighth most polluted place in the world.The study says makers of chemical products are responsible for more than a third of the contamination, and says tests indicate 80% of water taken from wells near the river is not safe.The study does say several cleanup programmes are making some "progress" with support from the World Bank. About 20 000 people live near the river basin, while 15 000 industries discharge effluent into the river, the report says.Environment Secretary Juan Jose Mussi last week accused the media and the report of exaggerating the river's condition. But he also concedes the pollution problem is "not solved".Can the Riachuelo be saved? Experts say yes, although much needs to be done."There's a long-term, high-cost solution that could take decades," said Raul Estrada Oyuela, a member of Argentina's Environmental Sciences Academy."This requires political will and thorough measures," Estrada Oyuela said. One of the measures would be a strict restriction on dumping pollutants and raw sewage.Today, muddy bubbles can be seen across the river's surface. "These are gases produced by heavy metals on the bottom," said Alfredo Alberti, president of the La Boca Neighbours Association.High levels of arsenic, chromium, copper, zinc and lead have been measured in the river.The pollution began in the 16th century, when people began throwing animal parts and fat into the water. That continued into the 19th century, when businessmen came to its banks to set up "saladeros", shops that produce salted meat. Over time, factories moved in and began dumping heavy metals and acid.Stunted growth, dermatitusThe spur for the current cleanup came five years ago, when Argentina's Supreme Court ordered the national government and Buenos Aires city and provincial officials to work with the Authority of the Matanza-Riachuelo Basin to make the river sparkling clean.Environmentalists warn there's a long way to go before the river is even somewhat clean.While they agree progress has been made, including the recent removal of sunken ships from the river and garbage from its surface, they are pushing for a more extensive cleanup and want a petrochemical hub moved far away from the river.Green Cross Argentina's president, Marisa Arienza, said the most urgent problem is lead contamination, which can stunt growth in children and causes bleeding of the gums and dermatitis.A full cleanup could take 30 years, said Lorena Pujo, a Greenpeace co-ordinator, because factories need to come up with ways to dispose of waste other than dumping it in the river. Then, crews will have to clear out tons of contaminated mud on the river bottom."What's most important is that we reach a consensus that there can be no industrial pollutants coming into the water," Pujo said.The river agency says 891 businesses "are working in an industrial conversion plan to stop contaminating" and 411 have already changed their production processes. So far, $225m has been spent on cleaning the river, making water supplies safer and treating sewage, it says.Some experts, including Arienza of Green Cross Argentina, contend the report on most-polluted places understates improvements in the Riachuelo and fault the authors for basing the rankings on old data and not doing their own tests.But ultimately, Arienza said, the problem is clear."There's no doubt that it's one of the most contaminated places in the world," she said, "although by now it's pretty irrelevant whether it's No. 8 or 20."