Location: Pasture Systems & Watershed Management Research
Project Number: 8070-21600-001-007-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 30, 2025
End Date: Sep 29, 2028
Objective:
Human exposure to per- and polyfluoroalkyl substances (PFAS) occurs through a variety of routes, including indoor dust and air, drinking water, and diet. For the public, the main route of exposure to PFAS is through dietary intake (food and water). However, due to the widespread use of these compounds in industrial settings, there is significant risk of exposure occupationally through the manufacture and handling of PFAS-containing products. Most studies have focused on environmental exposure from drinking water, but there is a paucity of data on inhalation exposure and direct contact with material containing PFAS, especially in occupational settings. Biomonitoring studies of firefighters have found differences in exposures as compared to the general population with elevated serum levels of some PFAS through exposure to firefighting foam and combustion of PFAS containing materials. Agricultural workers may be exposed to PFAS in a manner similar to that of firefighters through aerosolization and/or volatilization of PFAS during the application or use of biosolids. Although limited studies have shown that farmers are exposed to PFAS, to our knowledge there has been no examination of the impact of different agricultural practices on their total burden of PFAS.
Silicone wristbands are increasingly used as passive monitoring devices for assessing micropollutant exposures in a variety of settings including occupational and vulnerable populations. Importantly, these samplers have been used to assess pesticide exposure in agricultural workers. In one previous study, seven PFAS were detected in wristbands and perfluorooctanoic acid (PFOA) levels increased during active duty. We will rely on this study as it is the first to specifically examine PFAS detection and their recovery from silicone wristbands. An advantage of this approach is that it looks at exposure from all sources (air, water, food) and can be deployed when the participants are performing different activities. Therefore, we aim to use silicone wristbands as a way to establish links between pre-harvest activities conducted by agricultural workers and PFAS exposure levels. We hypothesize that relative to other pre-harvest activities, PFAS exposure is highest during application of human waste residuals, including land-application of biosolids.
Overall, the project will focus primarily on two over-arching research questions: (1) what guidance can be provided for appropriate crops to be grown for sites that have been receiving land-application of biosolids to best utilize these resources and minimize impacts to livestock and human health; and (2) what are the occupational hazards associated with land-application of biosolids or spray-irrigation of treated wastewater for the operators of these facilities, and how can exposure to those hazards be reduced? Knowledge generated through this proposal will be used to inform best practices for on-farm management of biosolids to mitigate PFAS in the food supply and protect human and ecological health.
Approach:
The agricultural workers recruited to participate in this project will be provided informed consent prior to participating in the study, which will undergo review by the Pennsylvania State University Institutional Review Board. Participants will complete a survey for each of the periods for which they wear a wristband to establish links between pre-harvest activities and per- and polyfluoroalkyl substances (PFAS) exposure levels. The participants will be provided with commercially available silicone wristbands, which will be pre-cleaned through two twelve-hour lipid extractions using first 1:1 ethyl acetate/hexane (v/v) and then 1:1 ethyl acetate/methanol (v/v). Wristbands will be dried in a vacuum oven at room temperature, wrapped in pre-cleaned aluminum foil and stored in airtight jars until distribution to study participants. After wearing the wristbands, participants will be asked to rewrap the wristband in provided aluminum foil and enclose it in a plastic zip-top bag. Samples will be stored in a freezer before being transported to the Pennsylvania State Environmental Contaminants Analytical Laboratory (ECAL) for processing and PFAS analysis.
Through our partnership with a regional wastewater treatment plant, we will work with 14 partner farms on which biosolids are applied. It is likely that the biosolids applications are done by a handler and not by the workers who conduct day-to-day operations at the farm itself. Therefore, we anticipate needing to assess exposure separately for the biosolids handlers/applicators and the on-farm agricultural workers. Each participant will be provided with silicone wristbands at the beginning of the study, along with prepaid mailing kits to return the wristbands to the Cooperator for analysis.
Biosolids Handlers/Applicators: We will recruit a total of 20 biosolids handlers/applicators and ask them to wear wristbands for one-week prior to applications and for a one-month period when they conduct applications, assuming each handler applies biosolids at multiple sites. This will allow us to assess the total PFAS exposure that each of these handlers is experiencing during application activities relative to their exposure level prior to commencement of these activities.
Biosolids On-Farm Agricultural Workers: We will recruit one agricultural worker from each of the 14 partner farms to wear a wristband during all on-farm activities throughout the growing season (April through October). The participant will wear a wristband for one week prior to biosolids applications occurring on their farm to help determine pre-application exposure levels and then will change to a new wristband before biosolids application and every two weeks thereafter, continuing to wear the wristbands during all on-farm activities, for a total of 15 wristbands per growing season.
Wristband Extraction and Analysis. Each wristband will be cut into two fragments (~0.75 g), weight recorded and transferred to a glass centrifuge tube for extraction, as detailed elsewhere. One sample will be spiked with isotopically labeled internal standards. The other sample will be kept for re-analysis, if needed.