The following is based on a note in the October-December 1991 issue of Agroforestry Today (reviewed in EDN 23-3,4), which is in turn based on an article in The Economist (July 6, 1991 pp 86,87) and The Lancet (May 30, 1987 pp 1257-58).
“Farmers near Kabale in Kenya describe traditions, now considered superstitious, that certain euphorbias cause cancer when planted near the homestead.” [Euphorbias in Africa fill many of the environmental niches that are filled by cacti in the Americas.] Now the carcinogenic effects of one common living fence species, Euphorbia tirucalli, have been described. The active carcinogen has been found not only in the plant itself, but in extracts from nearby soil, vegetables and drinking water. “The report suggests that Burkitt’s lymphoma, a common childhood cancer in East Africa, is caused in part by consumption of water and vegetables from sites near this euphorbia.”
The plant grows profusely in Kenya’s Eastern, Western and Nyanza Provinces and in parts of Tanzania. In southwestern Uganda it is widely planted as a living fence to exclude livestock from protected springs, suggesting the frightening prospect that water that has been assumed safe is in fact very hazardous. It is also commonly used as a living fence to protect food crops.