In this photo taken Thursday, Nov. 12, 2015, Joyce Njeri, 8, walks with a torn sack carrying the plastic bottles she has scavenged, at the garbage dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, a boy who scavenges for a living dives off the makeshift raft he and his friends have made for fun, into a dark and polluted pool of water left by recent rains, at the garbage dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, Joyce Njeri, 8, walks with a torn sack carrying the plastic bottles she has scavenged, at the garbage dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, a boy who scavenges for a living is submerged after diving off the makeshift raft he and his friends have made for fun, in a dark and polluted pool of water left by recent rains, at the garbage dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, men and women scavenge for recyclable materials amidst mountains of garbage at the dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, Agnes Njoki, 17, carries her daughter Shantel Akinyi, 2, with her as she works scavenging for plastic at the garbage dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, Joyce Njeri, 8, enjoys a rare moment of fun playing like a child with Shantel Akinyi, 2, on a pile of discarded sheets of plastic left over from the manufacture of flip-flops, at the garbage dump where Joyce herself and the mother of Shantel both work, in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, a man who scavenges for a living takes a rest next to a Marabou stork on top of a mountain of garbage at the dump in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)

In this photo taken Thursday, Nov. 12, 2015, Joyce Njeri, 8, enjoys a rare moment of fun playing like a child with Shantel Akinyi, 2, on a pile of discarded sheets of plastic left over from the manufacture of flip-flops, at the garbage dump where Joyce herself and the mother of Shantel both work, in the Dandora slum of Nairobi, Kenya. Men, women and children traipse through the murky sludge that weaves through mountains of garbage in Nairobi's notorious Dandora dump, hunting for anything that can be recycled to earn themselves enough for their daily bread - some of the poorest of Kenya's poor and those likely to be on Pope Francis' mind when he makes his first trip to Africa this week and brings his message of environmental stewardship and care for society's most marginal. (AP Photo/Ben Curtis)