Why are biosolids not spread on crops grown for human consumption when toxic chemicals are present?

Biosolids, which are the residues remaining from wastewater treatment, are not spread on crops grown for human consumption when toxic chemicals are present primarily to prevent the entry of these contaminants into the food chain.21

When biosolids contain heavy metals, synthetic organic chemicals, or other xenobiotic chemicals, they pose significant health risks because these substances can bioaccumulate in the environment. Plants can absorb these pollutants from the soil through their roots, and the chemicals may subsequently accumulate in the fatty tissues of animals or humans who consume the contaminated crops.2341

Because many of these toxins are persistent and lipophilic, they are not easily broken down and can remain in the body for long periods, potentially leading to serious health issues such as cancer, birth defects, and nervous system disorders. Consequently, strict management and processing are required to reduce concentrations of these harmful substances before biosolids can be considered for agricultural use.312