The theory goes...
Fish bones are full of calcium phosphate.
The lead in the soil binds with the phosphate and transforms into pyromorphite, a crystalline mineral that will not harm anyone even if consumed.
This alchemy has been practiced in university and commercial laboratories for more than 15 years, and more recently has been employed at acid-mine sites and military bases.
But now it is also coming to residential neighborhoods like South Prescott in Oakland, which this month became the first in the country where fish-bone meal is being mixed into the soil for lead control under a project organized by the Environmental Protection Agency.