Heavy Metal in Fertilizers: Considerations for Setting Regulations

Figure 1 – Pathways for loss of heavy metals from a fertilizer application sites 3 Table 1 – Background concentrations for five heavy metals in Oregon soils and Oregon Department of Environmental Quality 6 Table 2 – Water quality criteria for five heavy metals in freshwater 7 Figure 2 – Profound effect of K d on the RBC for cadmium in the low range of estimated K d values 15 Table 3 – Distribution Coefficients and Plant Transfer Coefficients for Heavy Metals in Agricultural Soils 16 Table 4 –Schematic of information collection in a risk assessment 17 Figure 3 – Profound effect of PUF on the RBC for cadmium in the low range of estimated PUF values 20 Figure 4 – Estimated K d for cadmium strongly influences model simulation of accumulation of the metal in soil over time 22 Figure 5 – Demonstration that the relationship between half-life for cadmium in soil and RBC is essentially identical to the k d /RBC relationship 23 Figure 6 – There is a linear relationship between the half-life and K d for cadmium in soil 24 Conclusions and Recommendations 25-28 Figure 7 – Simulation of arsenic accumulation in soil over time after application of 75 grams of 20% phosphate product containing 260 mg/kg arsenic once a year 26 References 29-32 Appendix 1 33-35 1 Heavy Metals in Fertilizers: Considerations for Setting Regulations in Oregon Executive Summary Concentrations of heavy metals in fertilizers, agricultural minerals, agricultural amendments, and lime products are subject to regulation by state governments. Oregon Department of Agriculture must adopt standards for arsenic, cadmium, lead, mercury, and nickel concentrations in these products during 2002. The objective of this regulation is to protect human health and natural resources from toxicity of these heavy metals. Since use of fertilizers and related products is a repetitive practice, it is necessary to consider cumulative changes over decades of applications. There is a significant body of scientific literature on transport, fate and effects of arsenic, cadmium, lead, mercury, and nickel. Integration of this information into models that represent behavior of these heavy metals in agricultural systems provides a rational approach to establishing unacceptable concentrations in fertilizers and related products. This involves screening available information, and identification of areas in which data limitations create uncertainty. Human health risk assessment integrates information on environmental chemistry and toxicology of the metals of interest with estimates of product application …