Soils, water, and bedrock naturally contain these elements in varying concentrations. They include metals like arsenic, cadmium, copper, lead, mercury, molybdenum, nickel, selenium, and zinc. Trace metals are present throughout the environment including soils, food, drinking water, humans, animals, plants, and biosolids. Yes, biosolids contain trace concentrations of metals. The trace metals found in biosolids come from both industrial and residential sources.
Commercial industry is a major contributor of trace metals.
Residential contributions originate primarily from common household products. Control of residential contributions of trace metals to biosolids is accomplished largely through public education and household hazardous waste collection programs. Trace metals in excessive concentrations in our environment or in biosolids are a concern for the health of plants, animals, and humans. If trace metals occur in concentrations higher than the desirable range there is an increased risk of negative impact. Concentrations of trace metals in biosolids are below any level of concern.