NAIROBI, Kenya — Using hooks or their bare hands, men, women and children traipse through the murky sludge that pools around the mountains of garbage, hunting for bottles, plastic bags and anything else that can be recycled to earn themselves enough for their daily bread.

The scavengers at Nairobi’s notorious Dandora dump are some of the poorest of Kenya’s poor – and they are likely to be on Pope Francis’ mind when he makes his first trip to Africa Thursday to bring his message of environmental stewardship and care for society’s most marginalized. His message will take on an even more poignant ring on a continent long wracked by poverty, war and disease.

One of Francis’ most anticipated speeches will be to the Nairobi-based U.N. Environment Program, which has warned that those working and living near Dandora suffer from a wide range of diseases including lung cancer, skin diseases and lead poisoning that cause stunted growth and mental disabilities in children.

Francis has denounced how the poor suffer disproportionately from environmental degradation, especially the health effects of pollution, and at UNEP he is likely to call for governments to clean up their act ahead of crucial climate negotiations opening in Paris next week. He warned in his landmark encyclical “Praise Be” that the dumping of toxic, radioactive and industrial waste risks turning Earth into “an immense pile of filth.”

About 3,000 Kenyans must try to avoid used intravenous needles, diapers, surgical knives and other hazards as they pick through the 2,000 tons of garbage dumped here daily. They work alongside hundreds of Marabou storks that scavenge.

They are reluctant to accept that their bodies might be withering as a result of the waste, fearing that such an admission will convince the county government to shut down the dump – and their livelihoods. “I used to have nothing,” said Mary Nyambura, a 47-year-old widowed mother of seven. She said the dump is her only means of survival. “But if I come here I am assured of at least $1 that can feed my family.”

An area legislator, James Gakuya, launched a lawsuit against the county government in 2014 seeking to close the dump, arguing that it was damaging the health of his other constituents in nearby residential areas.

There was a proposal to relocate the dumpsite to the outskirts of the city. But the Kenya Airports Authority said the proposed locale was on a flight path for planes taking off and landing, and that the massive Marabous that circle overhead would endanger aircraft. The proposal was shot down.

The pope knows well the plight of garbage pickers, having ministered for years to the “cartoneros” of Buenos Aires, who also pick through garbage. Just last month, he baptized the son of the leader of the “cartoneros” in a small ceremony inside the Vatican.