Progress report for GNE19-209
Agricultural soils may be contaminated with chemicals that pose risks to farmers. Ensuring safe and sustainable agricultural practice necessitates knowledge of farmers’ activities and behaviors that drive soil contact as well as data regarding the concentrations of contaminants in agricultural soils. Filling these knowledge gaps requires a mixed methods approach and involves innovation through updating of existing soil contact tools to collect data specific to this context.
Little is known about the specific activities and behaviors that dictate soil contact among agricultural workers. Typically, behavioral data used in safety assessments would be drawn from default assumptions from the US EPA Exposure Factors Handbook (which provides estimates of inhalation, ingestion and dermal contact rates for soil for adults and children in the general US population). These estimates are unavailable for farmers, who would be expected to have greater rates and frequency of soil contact (US EPA 2011a). Researchers have estimated dermal exposure to soil while engaging in several soil-related activities, but these estimates are highly uncertain, based on limited data, and likely irrelevant to the agricultural context (Holmes et al. 1999; Kissel et al. 1996; Kissel et al. 1998; Kissel 2011). The nationally-representative Soil Contact Survey (Garlock et al. 1999; Wong et al. 2000) was used to estimate the frequency and duration of soil contact among the US population, but was not designed to characterize direct soil contact among farmers.
No researchers have investigated farmers’ soil contact activities and behaviors and no survey or occupational assessment tool exists to do so. This exploratory and innovative research seeks to describe the activities of farmers (e.g., planting, harvesting, watering, etc.) to inform the development of a survey to generate activity pattern data and quantify rates (e.g., frequency and duration) of soil contact for each of those activities. This task or activity-centered approach to farmers’ work activities will deepen our understanding of soil contact in an agricultural context and improve methods for the assessment of occupational health exposures and risks in the future. Identifying key activities and behaviors that contribute the most to soil exposures will inform more specific, evidence-supported and practicable exposure mitigation strategies. While this project investigates the presence of metal contaminants in soils, we believe the activity and behavior information we generate could also support the derivation of health-based guidance values for non-metal contaminants that are deliberately intended to protect farmers.
Objective 1. Describe the activities and behaviors of rural farmers that impact soil exposure.
Objective 2. Quantify the activities and behaviors of rural farmers that impact soil exposure.
Objective 3. Compare activities and behaviors of rural and urban farmers that impact soil exposure.
Objective 4. Measure and compare concentrations of soil contaminants on urban and rural farms in Maryland
The purpose of this project is to investigate and contextualize environmental health risks associated with exposure to potential soil contaminants among urban and rural farmers. Most occupational investigations of health risks among agricultural workers have focused on accidents, injuries, and exposure to pesticides in rural locations (Alavanja et al. 1996; Alavanja et al. 1999; Racine et al. 2012). For farmers, direct soil contact is an important, but poorly characterized source of exposure to potential soil contaminants. Urban soils may be contaminated with heavy metals (e.g., lead and arsenic) due to their natural occurrence, as well as current and historical industrial activity (e.g., fossil fuel combustion and waste incineration), and legacy uses of lead-based paint and leaded gasoline (Mielke et al. 1983; Mielke and Reagan 1998; Mielke et al. 2011; Schwarz et al. 2012; Yesilonis et al. 2008). The increased interest in and practice of urban agriculture (Palmer 2018) has raised concerns about risks stemming from farmers’ exposure to soil contaminants and exposures resulting from consumption of urban-grown fruits and vegetables (Kim et al. 2014). Rural soils may be contaminated with heavy metals due to current and historical and applications of persistent pesticides (e.g., lead arsenate) or from previous land uses or contamination events unknown to the farmer (Hood 2006; McBride et al. 2015). Given increased interest in local, sustainable food production, and the simultaneous loss in agricultural land (particularly in the Northeastern US) to other non-agricultural land uses (America’s Farmland Trust 2018), new and younger farmers may take on rehabilitation of land for which the previous land uses are unknown.
No public or occupational health agency is responsible for surveillance and routine monitoring of contaminants in agricultural soils. Soil contaminant testing is highly recommended by the US EPA before establishing any urban agriculture project (US EPA 2011b), but comparable guidance is not available for rural farms. Interpretation of contaminant results is difficult because current health-based guidelines for contaminants in soil can vary widely by jurisdiction and designated land use (Jennings 2013a, b). No guidance values for soil contaminants exist for agricultural land that are intended to protect farmers. To inform evidence-based guidelines for contaminants in soil, research is needed to understand the nature and extent (e.g., the frequency, duration, and intensity) of soil contact among farmers in urban and rural contexts. The conduct of this research will provide participating farmers with soil contaminant testing services. These individual results can be used to inform soil conservation and management decisions in the short term. The long-term impacts of this research will improve the health and well-being of farmers by increasing our understanding of farmers’ interactions with soil contaminants as a potential contributing factor to acute and chronic illness and disease. More importantly, this research will generate information about farmers’ soil contact necessary to inform evidence-based recommendations to reduce exposure that are practicable for farmers in both urban and rural contexts and can be used to improve the quality of life for farmers and their employees.
Objective 1. In January - February 2020, we conducted in-depth interviews with 16 farmers in Maryland about their soil contact activities and behaviors. Interview recordings were transcribed verbatim using nVivo and analyzed using a framework approach. A manuscript has been published, and one other is in progress.
Objectives 2-3. Between May 2020 and January 2021, we administered 130 soil contact activity questionnaires to 38 farmers in Maryland. A manuscript summarizing these results is in progress.
Objective 4. To comply with CDC recommendations and university restrictions on in-person contact for research due to the COVID-19 pandemic, the administration of a seasonal soil contact activity questionnaire was conducted via phone, beginning in May 2020. As of 12/31/2020, 38 farmers have been recruited and 3 seasons (spring, summer, and fall) of the questionnaire have been administered. Administration in the final (winter) season will begin in January 2021.
The collection of soil samples from farms was postponed until spring 2021 due to the COVID-19 pandemic. In May 2021, soil sampling kits were sent via US mail to 24 farmers who had previously completed questionnaires and agreed to provide a soil sample. 18 farmers provided a soil sample. All soil samples were analyzed for the concentrations of 12 metals (6 harmful to human health: As, Ba, Cd, Cr, Pb, and Ni; and 6 not harmful to human health: Ca, Co, Fe, Mn, K, Zn) using Inductively Coupled Plasma- Mass-Spectrometry (ICP-MS).
Objective 1. Our interviews identified four emergent themes relevant to soil exposure in agricultural context: 1) variability in growers’ descriptions of soil and dust, (2) variability in growers’ soil contact, (3) growers’ concerns regarding soil contact, (4) growers’ practices to modify soil contact. We also identified environmental and behavioral factors and six specific agricultural tasks that may impact soil ingestion rates. These considerations were incorporated into the soil contact activity questionnaire that was administered for Objectives 2-3.
Objective 2. TBD
Objective 3. TBD
Objective 4. Because there are soil concentrations were compared to Maryland Residential Soil Standards and background levels in Maryland and returned via email directly to farmers. All concentrations were below the soil safety standard for Ba, Cd, Pb and Ni. All but one sample had As concentrations greater than the residential soil standard but were within or below background levels for the state of Maryland. Concentrations of all not harmful metals were below the residential soil standards (Cu, Fe, Mg, Zn). A short communication piece is in progress.
Education & Outreach Activities and Participation Summary
Building upon the network established by PI Nachman as part of the Safe Urban Harvests study in Baltimore, we anticipate a wide array of audiences and venues for translating and communicating the results of this research. Outlets for communication will include (but may not be limited to) direct report-back to participants, presentation at local urban agriculture community events, presentations at sustainable agriculture conferences, and publication of findings in peer-reviewed manuscripts. Updates will be provided as these educational opportunities are provided.
- Key considerations for assessing soil ingestion exposures among agricultural workers (Peer-reviewed Journal Article)