(Adds colour, quotes, changes dateline from GENEVA)

By Ingrid Melander

THIAROYE SUR MER, Senegal, June 24 (Reuters) - The World Health Organisation urged Senegal on Tuesday to decontaminate a suburb where nearly 1,000 residents remain exposed to high concentrations of brain-damaging lead after 18 children died.

International health and environmental experts carried out an investigation last week in the NGagne Diaw quarter of Thiaroye sur Mer, where authorities banned a local industry recycling lead batteries in March over health concerns.

"Many children are showing evidence of neurological damage. Environmental investigations have found very high concentrations of lead both outside and inside people's homes," the WHO said in a statement issued at its headquarters in Geneva.

Some 950 people in the poor area are "continuously exposed through ingestion and inhalation of lead-contaminated dust," it said. "Thorough decontamination of the affected area of NGagne Diaw, including the insides of homes, is a high priority."

In Thiaroye's sandy, litter-strewn alleyways, local people said recycling lead had been a way to survive Senegal's poverty.

"I was doing it because I had no job, I didn't have a choice. If it hadn't been forbidden I would still be doing it," said Seynabou Mbengue, 44, as she showed a bag containing recycled lead. She said the work never made her ill.

Nearby a battery lay half-submerged in a waterlogged ditch.

Demba Diaw, a teacher in a Koranic school, said his only child, a daughter, died aged 4 from lead poisoning. He and other grieving parents campaigned to end recycling in the area.

"These are very toxic substances. They can cause cancer, malformations, reproduction problems, problems of growth for kids," said Henry Diouf of the Pesticides Action Network-Africa.

Two years ago Diouf investigated lead poisoning in another part of the sprawling coastal city. "Most of these women told us they were conscious that this activity was dangerous but they were doing it because they had no other option," he said.

"We must put a lot more effort into helping people understand the danger and also help them find other activities."

YOUNG MOST AT RISK

At least 31 children need treatment for lead poisoning but not everybody has been examined, Joanna Tempowski, a scientist in the WHO's environmental health emergencies division, said.

"The focus is on small children because they are very vulnerable to lead poisoning because neurotoxic substances can affect child development even at quite low levels, and these are very high levels," she told Reuters.

Senegal needs urgent help to clean up, the WHO said.

"The recycling has stopped but the lead is in the environment and won't disperse. It needs to be removed. It is an enormous job," said Tempowski, who stressed that some of the batteries may also contain other contaminants such as arsenic.

Senegal's health ministry reported to the WHO in March that a total of 18 children died between last October and February, WHO spokeswoman Sari Setiogi said.

Siblings and mothers of the dead children had "extremely high blood level concentrations" -- in many cases more than 10 times the level which may impair neurological development, according to the Geneva-based United Nations agency.

Children with high lead exposure may need chelation therapy, which removes heavy metals from the body, it said. But it warned the treatment would be "ineffective and may exacerbate toxicity" in children who are still exposed to lead.

The agency has provided chelating agents and its clinical toxicologist has started training local medical staff, it said. (Additional reporting by Stephanie Nebehay in Geneva, Editing by Laura MacInnis and Diana Abdallah)

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