Madison, Wisc.-Long-term studies have found that concerns are unfounded about dioxins accumulating in the soil and getting into the food supplies from use of biosolids as fertilizer, according to the American Society of Agronomy. The society pointed out that until recently there has been very little information available on the effect of long-term application of biosolids on accumulation of dioxins in soil and uptake by plants. Now findings from an investigation by the Metropolitan Water Reclamation District of Greater Chicago utilizing established plots suggest that dioxins from land application of biosolids do not pose any risk to human health or the environment, if biosolids are land applied according to EPA regulations. The study revealed that the levels of dioxins in soil from the control and agronomic rate biosolids plots were not statistically different, but the soil levels of dioxins were much higher in the plots that have been receiving four times higher rates of biosolids application. Dioxins were not detected in the corn grains. Only trace levels were found in the corn stover, and there was no statistical difference between the control and the biosolids-amended plots. The district has on-going research to investigate the trend of dioxins levels in biosolids over time. The USEPA’s 2001 Dioxins Update to the National Sewage Sludge Survey indicated that dioxin levels in biosolids have declined since the last USEPA survey in 1988. This downward trend is expected to continue due to the regulatory controls on additional sources of dioxins in the environment, particularly on some combustion practices. These findings support the USEPA’s decision not to regulate dioxins in land applied biosolids.
Transparency Across the Fertilizer Value-Chain