Fish bones versus lead

Lead is a metal with no known biological benefit to humans. Our understanding of how a small amount can cause harm, to young children and pregnant women in particular, only came about during the past few decades. Now, lead-free paint and cosmetics and unleaded fuel have resulted in lead poisoning becoming much less common than it used to be. That does not mean, however, that the lead already in our environment has disappeared.

One area of concern is the residual lead in contaminated soil, especially in urban and industrial areas. The lead content may have come from leaded fuel, paint or from nearby industries such as foundries or smelters before the environmental hazards were recognised. It would cost a huge amount economically and socially to remove all the contaminated soil, and since topsoil is a precious resource it could be even more costly to replace it.

A possible solution is now being tested in South Prescott, a suburb of Oakland, California, using fish bones from the Alaskan pollock. When pollock is processed for fillets, soups and sandwiches, and as food for Japanese fish farms, all remnants of flesh are removed by large industrial blowers leaving clean dry bones rich in calcium phosphate. When these bones are spread on contaminated soil the lead binds with the phosphate to form pyromorphite, a harmless crystalline mineral. The same theory was applied when ground crab shells were dug into contaminated soil in Michelle Obama’s vegetable garden at the White House.

South Prescott was built on landfills holding the detritus of the 1906 San Francisco earthquake and is reckoned to have soil contaminated with up to six times the federal limit of lead. This project is expected to cover a six-block area and cost $4m over two years. It will also train up to 75 workers, many previously unemployed, in toxic clean-up methods.