Risk assessment of potentially toxic elements (heavy metals and arsenic) in soil and fertiliser products – fate and effects in the food chain and the environment in Norway - Scientific opinion of the Panel on Animal Feed of the Norwegian Scientific Committee for Food and Environment

Key words: VKM, risk assessment, Norwegian Scientific Committee for Food and Environment, Norwegian Environment Agency, potential toxic elements (PTEs), fertiliser, soil improver, fertiliser products, growing media, circular economy, circulation of organic fertilisers, arsenic (As), cadmium (Cd), chromium Cr(tot) (Cr(III) and Cr(VI)), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni), zinc (Zn). Background and purpose of the report The potentially toxic elements (PTE) arsenic (As), cadmium (Cd), chromium Cr(tot) (Cr(III) and Cr(VI)), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn) occur as ingredients or contaminants in many fertilisers, soil improvers, engineered soil and growing media. Application of these fertiliser products might represent a risk towards the environment, farm animals and humans, particularly when applied annually over several years. The present risk assessment evaluates the application of selected fertilisers according to certain scenarios for representative Norwegian agricultural areas, from Troms in the North to Ås in Southeastern and Time in Southwestern Norway, with different soil properties, precipitation and PTE concentration in present agricultural soil. There is an increasing trend to produce locally (e.g. in urban farming) and home-grown vegetables that are cultivated in engineered soil and growth media. The maximum levels (MLs) set for PTEs in different organic fertilisers, engineered soil and growing media for use in urban farming, home growing and the cultivation of vegetables and garden fruits, and a set of MLs also for application in agricultural cultivation of crops, have been evaluated. Environmental fate processes and the transfer of PTEs have been modelled and the environmental risks for terrestrial and aquatic organisms, including from secondary poisoning have been estimated. Potential risks to humans and farmed animals by increased exposure to PTEs from, respectively, agriculturally produced crops, vegetables cultivated at home and urban farming or forage and grazing have been evaluated. The recycling of nutrients is urgently needed to achieve circular economy, but the derived sustainable products have to be safe, which requires the introduction of and adherence to science-based maximum levels of unwanted substances (e.g. pollutants). This assessment evaluates consequences of the application of different fertiliser products: mineral P fertilisers, manure from cattle, pig, poultry and horse, fish sludge, digestates and sewage sludge - in order to identify PTE sources with potential environmental, animal and human health risks, and to evaluate the appropriateness of the current MLs regarding different applications of organic-based fertilisers, engineered soil and growing media at present, and in a 100-year perspective. Approach and methods applied The approach for environmental and health risk assessments builds on previous work performed for hazardous substances in soil (e.g. VKM 2019, VKM 2014, VKM, 2009, Six and Smolders, 2014). Concentrations of PTEs in soil over time were calculated using a mass balance model, which considers the input by atmospheric deposition, use of fertilisers and soil improvers, as well as loss by leaching, run-off and plant uptake. The resulting first-order differential equation was solved analytically and implemented into Excel®. Run-off and loss by leaching were estimated from data on precipitation, infiltrating fraction and run-off fraction of the water under consideration of the distribution coefficient Kd for the concentration ratio of bulk soil-to-water. This Kd value takes aging sufficiently into account and is thus more realistic than those derived from batch tests. The Kd was estimated separately for each region using established regression equations, with soil pH, organic matter content and clay content as predictors. ...........