A decision made in the 70s in a golf club in New York caused this. See some executives wanted to dump some radioactive waste. This waste doesn't decompose like your traditional compost. It has a half life that keeps changing and is highly carcinogenic
The execs approach various people and finally end up approaching a Kenyan politician who agreed to a 50k USD bribe. In return they were to send the waste into Chalbi desert. The bribe was so little that the execs didn't even go for a board meeting to approve it. They agreed to pay right there over a round of golf.
Back in Kenya the politicians didn't inform the citizenry of what was to happen. The residents of the are just saw heavily protected guys dumping some stuff in the ground covered in tarp. In North Eastern Kenya, houses are mostly makeshift since they're pastoralists. They see this tarp as a good cover to their manyattas and they start digging up the waste and taking the protective paper. This had near instant repercussions. People started to fall Ill and soon that waste found its way downstream to Meru. If you look at the prevalence rate of cancer along that waterway you'll understand that politician's don't care about their own people