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Uptake of perfluoroalkyl acids into edible crops via land applied biosolids: Field and greenhouse studies
Blaine, A., C. Rich, L. Hundal, C. Lau, Marc A. Mills, Kimberly M. Harris, AND C. Higgins. Uptake of perfluoroalkyl acids into edible crops via land applied biosolids: Field and greenhouse studies. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. John Wiley & Sons, Ltd., Indianapolis, IN, 47(24):14062-9, (2013).
Because of the high-profile nature of findings reported in this manuscript, the Office of Science and Policy at ORD is taking the lead to coordinate with Region 5, OCSPP, OW and OSWER and develop a list of key public health messages and communication strategy for the media when the paper is accepted for publication. Perfluoroalkyl acids (PFAAs), which have been used in stain repellents, non-stick food packaging, and fire-fighting foams,1 are ubiquitous and persistent in the environment; they have been detected in air, house dust, water, sediment, soil, wildlife, and human blood.2-4 In addition,longer chain PFAAs are poorly eliminated by many higher trophic level organisms, with elimination half-lives of more than five years in humans for some PFAAs.5 Toxicity to wildlife and laboratory animals is well established; adverse effects include reduced survival rates,fertility, and abnormal maturation3 The persistence, bioaccumulation, and toxicity of PFAAs make them high priority contaminants of emerging concern. PFAAs entering conventional wastewater treatment plants (WWTPS) or produced from precursors during treatment can exit the plant in either the aqueous or sludge phase,6 and the presence of PFAAs in municipal biosolids is well documented.7-9 Land application of biosolids has been practiced for decades; in the United States, approximately 60% of biosolids are land applied.10 Nutrient-rich biosolids are particularly attractive as a fertilizer for crop production. Currently, the United States Environmental Protection Agency (U.S. EPA) regulates land application of biosolids based on pathogen, metal, and nutrient content under 40 CPR Part 503)11 However, PPAAs in biosolids are not regulated)10 Furthermore, due to the persistence of PFAAs, repeated agricultural biosolids applications may present a potential exposure route for terrestrial food webs if PFAAs contaminate surface or ground water destined for animal or human consumption 12 or bioaccumulate in the edible portion of crops.
The presence of perfluoroalkyl acids (PFAAs) in biosolids destined for use in agriculture has raised concerns about their potential to enter the terrestrial food chain via bioaccumulation in edible plants. Uptake of PFAAs by greenhouse lettuce ( Lactuca sativa) and tomato (Lycopersicon lycopersicum ) grown in an industrially impacted biosolids-amended soil, a municipal biosolids-amended soil, and a control soil was measured. Bioaccumulation factors (BAFs) were calculated for the edible portions of both lettuce and tomato. Dry weight concentrations observed in lettuce grown in a soil amended (biosolids:soil dry weight ratio of 1:10) with PFAA industrially contaminated biosolids were up to 266 and 236 ng/g for perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA), respectively, and reached 56 and 211 ng/g for PFBA and PFPeA in tomato, respectively. BAFs for many PFAAs were well above unity, with PFBA having the highest BAF in lettuce (56.8) and PFPeA the highest in tomato (17.1). In addition, the BAFs for PFAAs in greenhouse lettuce decreased approximately 0.3 log units per CF2 group. A limited-scale field study was conducted to verify greenhouse findings. The greatest accumulation was seen for PFBA and PFPeA in both field-grown lettuce and tomato; BAFs for PFBA were highest in both crops. PFAA levels measured in lettuce and tomato grown in field soil amended with only a single application of biosolids (at an agronomic rate for nitrogen) were predominantly below the limit of quantitation (LOQ). In addition, corn ( Zea mays ) stover, corn grains, and soil were collected from several full-scale biosolids-amended farm fields. At these fields, all PFAAs were below the LOQ in the corn grains and only trace amounts of PFBA and PFPeA were detected in the corn stover. This study confirms that the bioaccumulation of PFAAs from biosolids-amended soils depends strongy on PFAA concentrations, soil properties, the type of crop, and analyte.