(Beyond Pesticides, May 14, 2014) New research conducted in Colorado by the U.S. Geological Service (USGS) that examines contaminant transport of biosolids ””otherwise known as sewage sludge”” in soils, has found that the toxic fertilizer can leave traces of household chemicals, antibacterial, and prescription drugs. The research adds to existing evidence of the hazards of sewage sludge fertilizer by demonstrating that chemical contaminants are sufficiently mobile and persistent that they can easily be transported to groundwater, with implication for local drinking water.
The study, entitled Dissipation of Contaminants of Emerging Concern in Biosolids Applied to Nonirrigated Farmland in Eastern Colorado, sampled regional wheat fields treated with sewage sludge processed in a nearby sewage treatment plant in order to determine contaminant levels and transport in soils. Researchers tested for a total of 57 contaminants of emerging concerns””chemicals that are increasingly being discovered in waters. Tests found chemicals ranging from antibacterial soaps, chemical cleaners, cosmetics, fragrances, and prescription drugs, such as the antidepressant Prozac and the blood thinner Warfarin, which had migrated down the soil column. In fact, 10 of the chemicals examined migrated to depths of 7 to 50 inches over 18 months after treated sewage sludge was applied.
“These compounds are not sitting in top layer, we see vertical movement down through the soil, which means there’s the potential to get into the environment — groundwater or surface water,” said USGS research hydrologist Dana Kolpin, Ph.D.
Previous research has already established the presence of contaminants in sewage sludge ranging from hormones, detergents, fragrances, drugs, disinfectants and plasticizers ””chemicals which are not eliminated during sewage treatment. However, USGS research provides further evidence of their persistence and mobility in the soil, never before been demonstrated.
“These are compounds that often come from us and that get sent to wastewater treatment plants that weren’t designed to remove them,” said lead author and hydrologist Tracy Yager, Ph.D.
Of all the chemicals tested, triclosan ””an antibacterial compound added to soaps, toothpastes, body washes and cosmetics”” was found at the highest concentrations in deeper soils, reaching 156 parts per billion in 7 to 14 inches of soil. Triclosan is a known endocrine disruptor and has been shown to affect male and female reproductive hormones, which could potentially increase risk for breast cancer. Triclosan is also shown to alter thyroid function, and other studies have found that due to its extensive use in consumer goods, triclosan and its metabolites are present in fish, umbilical cord blood, and human milk. Only recently has the U.S. Food and Drug Administration (FDA) proposed a new rule that requires manufacturers to prove that their products are both safe for long-term use and effective.
Meanwhile, as farmers in arid regions increasingly turn to sewage sludge for fertilizer, the study gives significant cause for alarm as the majority of Colorado residents get part of their drinking water from private wells which are not treated or routinely monitored for contaminants.
USGS chemist and coauthor of the study, Edward Furlong, Ph.D., commented, “We’re not telling anyone what they should do, but this study gives farmers some information about what some of the impacts could be.”
The only surefire way to avoid food grown with biosolids is to buy USDA organic certified product. On your lawn and garden be sure to scrutinize any lawn fertilizers which claim to be “organic” or “natural” but list ingredients such as “biosolids,” “dried microbes,” or “activated sewage sludge.” For more information on the hazards of biosolids read Beyond Pesticides’ Biosolids or Biohazards?
All unattributed positions and opinions in this piece are those of Beyond Pesticides.