Application and demonstration of meso-activity exposure factors to advance estimates of incidental soil ingestion among agricultural workers

BACKGROUND: Soil is an understudied and underregulated pathway of chemical exposure, particularly for agricultural workers who cultivate food in soils. Little is known about how agricultural workers spend their time and how they may contact soil while growing food. Exposure factors are behavioral and environmental variables used in exposure estimation. OBJECTIVES: To derive exposure factors describing how growers engage in different tasks and use those factors to advance the use of time-activity data to estimate soil ingestion exposures among agricultural workers. METHODS: A meso-activity-based, season-specific soil contact activity questionnaire was administered to 38 fruit and vegetable growers, asking for frequency and duration of six meso-activities and details on how they were completed. Questionnaire data were used to derive exposure factors and estimate empirical and simulated exposures to a hypothetical contaminant in soil via incidental ingestion using daily, hourly, and hourly-task-specific ingestion rates. RESULTS: Exposure factors characterizing the frequency and duration of six meso-activities by season, and self-reported soil contact, glove use, and handwashing practices by meso-activity and season, were generated. Seasonal average daily doses (ADDs) were similar across all three ingestion-rate approaches, and no consistent patterns of task-specific contributions to seasonal or annual ADDs were observed.