What to Know About ‘Forever Chemicals’ in Sludge Fertilizer

(Editors note: We are continuing to cover the Los Angeles fires. Scroll down for more on the latest.)

Societies have used nutrient-rich human waste as fertilizer for centuries. But sewage today is different. That’s because we’ve flooded the environment with complex chemicals that can end up in our sewage and wastewater and can’t be easily removed.

The contaminated waste is at the root of recent concerns over the “forever chemicals” that have been found in fertilizer made from sewage sludge, which is a byproduct of wastewater treatment.

The Environmental Protection Agency has long promoted reusing that sludge on the nation’s farmland, a practice that has several benefits. Sewage sludge is rich in nutrients, and using it on farms keeps it away from landfills or from being incinerated. Using sludge also means farmers need to use less synthetic fertilizer made from fossil fuel.

But for the first time, the E.P.A. said on Tuesday that the “forever chemicals” in sewage sludge can pose human health risks.

Its extensive draft risk assessment found that, while the general food supply isn’t threatened, the risk from contaminated fertilizer could in some cases exceed the E.P.A.’s safety thresholds “sometimes by several orders of magnitude.”