Environmentalists in Tanzania are mounting a campaign to rid the country of huge stockpiles of pesticides and other toxic leftovers, which officials say pose serious threats to citizens. Tanzania has more than 500 tons of agricultural compounds, including DDT, dumped or stored at more than 100 sites, enviros say. Most of the material was imported more than a decade ago from nations such as China and the U.S., and the stocks went unused because they were banned or no longer needed. Now they are stored in tattered sacks, corroding metal drums, or mountainous piles, many of them unlabeled and many of them near settlements and rivers. Enviros say that pesticides have already seeped into the soil and groundwater, and may be responsible for cancer and other diseases. Some enviros want to ship the waste to incineration facilities in Western Europe.