Since June 2010, Médecins Sans Frontières (MSF) has been treating children in Nigeria with the most severe cases of lead poisoning ever seen. "We started this knowing that we would have to learn as we went along. Even more children would have died if we hadn't taken immediate action," says Ellen van der Velden, who works as an emergency coordinator for MSF.

The lead poisoning was the result of small-scale gold mining operations. People chopped stones into small pieces and then ground them using kitchen equipment or machinery that was also used for grinding grain. However, the stones also contained lead. MSF is focusing mainly on children aged five or younger as lead poisoning presents the greatest threat to this age group. Van der Velden explains how the team set about their work.

How did MSF set up the project?

We contacted an international network of toxicologists for technical support. There is a treatment protocol for lead poisoning, but not for such high concentrations: 500 to 700 micrograms per litre of blood. A lead content of 100 can cause brain damage in children. Treating such high lead contents was therefore totally unknown territory. We collected as much data as possible for use in later scientific research.

How were the children treated?

The children were given medicine to remove the lead from their blood, three times a day for 19 days. We first admitted them to hospital for 28 days, but when we saw that there were almost no side effects, we changed our approach, step by step. In the end all the children were treated as outpatients. Treatment at home meant that mothers who had not yet brought their children to us were now prepared to do so as 28 days away from home is a long time if you also have to look after other children.

So a child is cured after 19 days?

Unfortunately not. The medicine only removes the lead from the blood, but the children have already been poisoned by the lead so much that it is also in other places in their bodies, for example their bones. Children therefore require more courses of treatment. After each round, we waited between one and five weeks before giving the next course of treatment. This gave the lead time to leave the bones and enter the blood. We took blood samples from the children once a week. If the lead levels had increased again, we started the children on a new course of treatment. The monitoring equipment was unable to deal with such high concentrations of lead, so we had to dilute the blood we took from the children with clean blood. We used this to measure the lead level, which we multiplied with the dilution factor. Real laboratory work.

I have worked for MSF for over 10 years and this has been one of the most complex and overwhelming aid projects that I have ever worked on. Our team arrived in one village and went into a house to ask to see all the children aged five or less. We couldn't: they had all died in the weeks before. Fortunately, the villagers are very strong and it has been encouraging to see that almost no children have died since we started the treatment.

MSF worked in Anka and Bukkyum, in the state of Zamfara. In December 2010 the team included 100 Nigerian and 16 international aid workers.