External costs of cadmium emissions to soil: a drawback of phosphorus fertilizers

Abstract

In this study the Impact-Pathway Approach methodology was applied for monetary valuation of health impacts due to cadmium emitted to soil as a micro-pollutant present in phosphorus fertilizers. Due to the high persistency of cadmium in soil, and high soil-to-plant transfer rates, humans are exposed to cadmium through their diet causing potential adverse health impacts. Future scenarios for cadmium emissions to soil via agricultural applications of inorganic and organic fertilizers in Denmark were defined. A simplified fate and speciation model allowed the increase in soil cadmium concentration to be calculated for each scenario. Human exposure was determined based on soil-crop bioconcentration factors for cadmium and dietary intake rates of Danish food crops. Updated doseeresponse functions linking lifetime cadmium intake to the probability of developing cadmium-induced renal disease and osteoporosis were applied. These impacts were converted into monetary values by using the EU standard value of a life-year adjusted for quality of life experience. Annualized cost per unit of phosphorus and cadmium are presented, discounted and undiscounted, for comparison. Application of struvite (magnesium ammonium phosphate) and mineral fertilizer produced the lowest external health costs, followed by the fertilizer products wastewater sludge and pig manure. The external cost estimates produced in this study could be used to design economic policy instruments to encourage use of cleaner fertilizer products.