Worms feed on what they find in the soil, according to Colorado State University-Pueblo Assistant Professor of Chemistry Chad Kinney. And these days, that can be anything from household disinfectants to prescription drugs. Kinney’s research on the transfer of contaminants in waste products to earthworms was featured in the February-March issue of Organic Gardening magazine.
A study of three Midwestern agricultural fields by Kinney and colleagues with the U.S. Geological Survey, in print with Environmental Science and Technology, found that biosolids used as agricultural fertilizer contain pharmaceutical and household contaminants, which explains why the earthworms they studied contained measurable amounts of phthalates, compounds widely used in cosmetics, plastics, and paints, as well as detergents, disinfectants, and pharmaceuticals. The researchers studied three sites -- a soybean field with no amendments of human or livestock waste, a soybean field amended with biosolids from a municipal wastewater treatment plant, and a cornfield amended with swine manure.
The researchers contend that because wastewater treatment plants are not designed to remove these compounds during sewage treatment, they move from the land applied biosolid into the food chain in miniscule amounts. Concentrations in the worms’ tissues ranged from 100 to more than 1,000 parts per billion, which could be significant to a robin or other songbird that eats 14 worms a day.
In order to reverse this impact, the magazine suggests that we use natural cleaners and dispose of leftover drugs by crushing them and mixing them with sawdust or kitty litter and discarding them.
Kinney said although it is unclear what, if any, effects these compounds might have on earthworms or organisms up the food chain, it is clear that these compounds are getting into the environment, and further studies are warranted.
“This is not necessarily just an issue for the wastewater industry,” he said. “It is one that all of us contribute to and, thus, should be concerned about.”
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