PARENT SESSION
TP2 - Bioaccumulation & Foodchain Contamination in Terrestrial Systems
Chair: Schull, Lee¹, ¹ , USA
2:10 PM to 5:30 PM - Tuesday, 19 November 2002
Room Ballroom J

(427) Food Chain Transfer and Risk Assessment of Arsenic, Cadmium and Lead in Commercial Fertilizers.

Shull, Lee^*,1, Jones, Mark¹, Bowland, Mark¹, ¹ MWH, Sacramento, CA, USA

ABSTRACT- Inorganic fertilizer materials, notably phosphate-based and micro-nutrient materials, are widely used globally and are essential for meeting the worlds food supply. Some crops (e.g., vegetable, root and vine crops) tend to require higher fertilizer application rates than other crops (e.g., grain crops). Depending on their origin, some of these fertilizer materials have been found to contain relatively high concentrations of problematic heavy metals, notably lead, cadmium, and arsenic. Therefore, application of these materials to farmland represents a potentially significant exposure pathway of human and ecological receptors to these metals. Over the past decade, the California Department of Food and Agriculture has investigated this issue, and the State legislature has enacted into law enforceable standards for lead, cadmium and arsenic called risk-based concentrations (RBCs), which are applicable to inorganic commercial fertilizers. In deriving these RBCs, both forward and reverse quantitative human health risk assessments (HRA) were performed. A forward, screening deterministic HRA was conducted for the purpose of focusing the scope of the assessment. Exposure pathways assessed included direct contact with amended soils and fertilizers, ingestion of plant and animal-derived food commodities, and ingestion of fish in water bodies containing fertilizer run-off. Of these pathways, the plant-related food-chain pathways dominated the theoretical risk estimations. This analysis also provided a basis for ranking the relative significance of food-chain pathways. Vegetable, grain and root crops were found to be more significant than vine, tree and forage crops. In addition, farm-family adults and children were assessed separately. A probabilistic, reverse HRA was performed on these food-related exposure pathways to derive the RBCs. Other important features of this study included modeling accumulation of metal concentrations in the root zone over many years of fertilizer application on California farms and developing probability density functions (PDFs) for modeling heavy metal uptake into food crops.

Key words: Foodchain, Risk assessment, Fertilizer, Heavy metals