"So it generally affects them," says Dr. Njoroge Kimani, the principal investigator for the study. "Whether from bacterial infections, whether from parasitic infections, whether from environmental toxicants, it does affect them in a big way."

These problems are particularly detrimental for children, who dig through this sludge without proper hand or foot protection.

"These kids, their systems are still developing. So the long-term effect of this exposure starts taking shape right from the time they are young. Which is the biggest problem," said Kimani.

Because the Nairobi River flows by the dumpsite, and is used to irrigate crops, it’s not just the scavengers who are harmed.

"There’s a lot of vegetables being grown there. And these vegetables end up in markets, various markets, sensitive spots around Nairobi, which people buy without knowing where it has come from," said Erick Wilson, the acting chairman for Folks Vision Kenya, a group helping young people in Dandora.

If the City Council goes through with plans to move the dump, Nairobians hope that better regulations and procedures are put into place this time

But for Joseph and so many others who depend on the dump for their livelihoods, they'd rather it stay here.