Before revision: Some biosolids have been found to contain persistent, bioaccumulative and toxic chemicals, radionuclides, and heavy metals , and such biosolids have the potential to contaminate soil and water when applied to land.
After revision: Some sewage sludge can not qualify as biosolids due to persistent, bioaccumulative and toxic chemicals, radionuclides, and heavy metals at levels sufficient to contaminate soil and water when applied to land.