Men search for metal at an abandoned lead mine in Kabwe, Zambia, the country's second largest city, in this undated photo. (See a map of Zambia.)
Decades of unregulated lead mining have led to widespread poisoning in residents exposed to soil and water.
The New York-based Blacksmith Institute added the city to its list of the ten most polluted places for 2007.
Blood lead levels in children, who often bathe in contaminated water and play in the soil, are high enough to be potentially fatal, the institute reported on its Web site.
Although a local nonprofit educates families about avoiding lead exposure, entire communities may have to relocate, the institute said.