Willis Ochieng, 10, scavenges through smoking refuse piled as high as a house at one of Africa's biggest rubbish mountains, his friends sitting nearby sucking on dirty plastic bottles of noxious yellow glue.

Located near slums in the east of the Kenyan capital Nairobi, the open dump receives some 2,000 tons of garbage daily. A U.N. study published on Friday says it is seriously harming the health of children and polluting the city.

"I have been coming here with my friends since I was eight," Willis told Reuters. "We come every day from the morning to the night. We come for plastic bags, anything metal we can sell."

As he spoke, maribu storks circled amid hundreds of red and green plastic bags blown by the breeze over the 30-acre Dandora site. At his feet, rats picked through the fetid, stinking heap.

"I want to go to school but I need money to buy food and help my mother," said the boy, dressed in a ragged grey T-shirt and shorts.

Friday's study, commissioned by the Nairobi-based U.N. Environment Program (UNEP), found that half of 328 children tested round the site had lead concentrations in their blood exceeding the internationally accepted level.

While hundreds of residents in the area rely on scavenging for income, it is mainly children who wade through the dump.

Exposed to pollutants from heavy metals and toxins in the site's soil, water and air, almost half the youths tested suffered from respiratory diseases including chronic bronchitis and asthma, UNEP said.

Nearly half the soil samples from the area had lead levels almost 10 times higher than unpolluted samples.

"The Dandora site may pose some special challenges for the city of Nairobi and Kenya as a nation. But it is also a mirror to the condition of rubbish sites across many parts of Africa and other urban centers of the developing world," said UNEP head Achim Steiner, exhorting city leaders to remedy the situation.

"ALARMING SITUATION"

"Urgent action is needed to reduce the health and environment hazards so that children and adults can go about their daily lives without fear of being poisoned and without damage to nearby river systems," he said.

Dandora waste gets into Nairobi River, polluting water used by locals and farmers further downstream, UNEP's report added.

At a nearby school, the dispensary has treated more than 27,000 people for respiratory problems in the last three years.

"We have been witnessing an alarming situation regarding Dandora children's health: asthma, anemia and skin infections are by now endemic," said the report's main author and local biochemist Njoroge Kimani.

"Since waste dumping is unrestricted and unmanaged, people are also at risk from contracting blood-borne diseases such as hepatitis and HIV/AIDS."

UNEP said a quarter of all diseases affecting mankind were attributable to environmental risks, with children especially vulnerable. Some 4.7 million children under five die each year from environmentally-related illnesses, it said, quoting World Health Organization (WHO) figures.

And 25 percent of deaths in poor countries are linked to environmental factors. Locals are pushing for the site -- where both the city and private companies dump waste -- to be closed.

"The poor are the best recyclers in the world," said a local priest, Daniele Moschetti. "Nothing of value goes to waste. But this should not put them and their families' lives in danger."

Kenya