Earthworms studied in agricultural fields have been found to contain organic chemicals from household products and manure, indicating that such substances are entering the food chain.
Manure and biosolids, the solid byproduct of wastewater treatment, were applied to the fields as fertilizer. Earthworms continuously ingest soils for nourishment and can accumulate the chemicals present in the soil.
The chemicals investigated are considered indicators of human and animal waste sources and include a range of active ingredients in common household products such as detergents, antibacterial soaps, fragrances, and pharmaceuticals. Some of the detected chemicals are naturally occurring such as plant and fecal sterols and fragrances. All of these chemicals tend to be concentrated in the municipal waste distribution and disposal process and are referred to as anthropogenic waste indicators (AWI).
U.S. Geological Survey Scientists and their colleague from Colorado State University at Pueblo published their new findings today in Environmental Science and Technology. The results demonstrate that organic chemicals introduced to the environment via land application of biosolids and manure are transferred to earthworms and enter the food chain.
Scientists found 28 AWIs in biosolids being applied at a soybean field for the first time and 20 AWIs in earthworms from the same field. Similar results were found for the field where swine manure was applied. Several compounds were detected in earthworms collected both from the biosolids- and manure-applied fields, including phenol (disinfectant), tributylphosphate (antifoaming agent and flame retardant), benzophenone (fixative), trimethoprim (antibiotic), and the synthetic fragrances galaxolide, and tonalide. Detergent metabolites and the disinfectant triclosan were found in earthworms from the biosolids-applied field, but not the manure-applied field.
Biosolids are made from the sludge generated by the treatment of sewage at wastewater treatment plants. Biosolids are used as fertilizer by farmers, landscapers, and homeowners when it satisfies U.S. Environmental Protection Agency and local regulations for nutrient, metal, and pathogen content. About half of the 8 million dry tons of biosolids produced in the U. S. each year are applied to the land. Biosolids have been found to be rich in AWIs compared to levels in wastewater treatment plant effluent. In addition, the 1.3 million farms raising livestock in the U. S. generate an estimated 500 million tons of manure annually, much of which is also applied to fields as fertilizer for crops.
This study is part of a long-term effort by the USGS Toxic Substances Hydrology Program to determine the fate and effects of chemicals of emerging environmental concern in aquatic and terrestrial environments, and to provide water-resource managers with objective information that assists in the development of effective water management practices. It was funded in part by a Research Corporation Cottrell College Award and a Faculty Research Grant from Eastern Washington University.
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