(Beyond Pesticides, February 28, 2008) Earthworms studied in agricultural fields have been found to contain chemicals from household products (including the widely marketed triclosan, a hazardous antimicrobial) and manure, indicating that such substances are entering the food chain. U.S. Geological Survey (USGS) Scientists and their colleague from Colorado State University at Pueblo published their findings in Environmental Science and Technology. The study results demonstrate that organic chemicals introduced to the environment via land application of biosolids, the solid byproduct of wastewater treatment, and manure as fertilizers are transferred to earthworms. Earthworms continuously ingest soils for nourishment and can accumulate the chemicals present in the soil.The scientists collected soil and earthworms from three agricultural fieldsâ€”a soybean field fertilized with biosolids, a corn field fertilized with swine manure, and a soybean field that had received no applications of either biosolids or manure for at least 7 years.
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. 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).
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. Earthworms from the control field (no recent application of biosolids or manure) contained detections of some of the same compounds, indicating potential persistence in the environment or another source.
In published studies, triclosan has been linked to skin irritations, allergy susceptibility, depression of the central nervous system, bacterial and compounded antibiotic resistance, and dioxin contamination as well as the destruction of fragile aquatic ecosystems. It has also been found in plasma and breast milk of nursing mothers and in urinary samples of three out of four individuals tested.
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 meets U.S. Environmental Protection Agency (http://www.epa.gov/OWM/mtb/biosolids/index.htm) 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. Triclosan cannot be removed from wastewater by conventional treatment processes.
The USGS results build upon a 2006 study that found 25 household chemicals in every biosolid sample collected including compounds that are pharmaceutically and hormonally active, such as such as triclosan, a musk fragrance (tonalide), an antihistamine (diphenhydramine), and an antiepileptic drug (carbamazepine).
When used outside of health care settings, triclosan is unnecessary, and constant exposure to triclosan becomes a health and environmental hazard. The best solution to preventing infections is plain soap and water.