The Environmental Concerns of Arsenic Additives in Poultry Litter: Literature Review

This review examines the scientific literature on the environmental concerns of arsenic additives in poultry litter. A number of questions were addressed on this issue. In summary, the review found: 1) Does arsenic from poultry feed amended with roxarsone end up in poultry litter? The arsenic found in poultry feed ends up in the poultry litter. Poultry litter from chickens receiving feed without roxarsone added contains only trace levels of arsenic, generally below detection limits of ≈ 1 mg/kg. Once roxarsone is added to the feed, the litter produced by the chickens contains total arsenic concentrations ranging from 2.9 to 77 mg/kg. 2) If poultry litter contains arsenic, is it present in an organic or inorganic form? Fresh poultry litter contains predominately organic roxarsone while aged litter contains predominately inorganic arsenic (As(III) and As(V)). Roxarsone is converted rapidly to inorganic arsenic both within the litter pile as well as after field application as fertilizer. This conversion is both bacterially mediated and through photolysis. Thus, very little arsenic from poultry litter remains as organic roxarsone after introduction to the environment. 3) When applied to agricultural fields, does arsenic accumulate in soils to a level of concern based on existing soil arsenic environmental soil criteria? A number of controlled experiments have shown that arsenic accumulates in soils once applied in poultry litter. Soil arsenic levels from litter amended fields are statistically greater than levels from unamended soils. This arsenic is predominately in the form of inorganic arsenic (As(III) and As(V)). Some areas on the Delmarva Peninsula which have received poultry litter for decades have accumulated arsenic to levels above both the Delaware and Maryland soil arsenic background remediation standards. A number of papers indicate that the use of arsenic as a feed additive is not a sustainable practice since arsenic concentrations continue to accumulate over time and soil levels will eventually increase to concentrations above these background remediation standards.