A task-based analysis of black carbon exposure in Iowa farmers during harvest

Abstract

Diesel exhaust has been associated with adverse human health effects. Farmers are often exposed to diesel exhaust; however, their diesel exposure has not been well characterized. In this descriptive study, we measured black carbon concentrations as a proxy for diesel exhaust exposure in 16 farmers over 20 sampling days during harvest in southeast Iowa. Farmers wore a personal aethalometer which measured real-time black carbon levels throughout the working day, and their activities were recorded by a field researcher. Black carbon concentrations were characterized for each farmer, and by activity, vehicle fuel type, and microenvironment. Overall, 574 discrete tasks were monitored with a median task duration of 5.5 minutes. Of these tasks, 39% involved the presence of a diesel vehicle. Farmers’ daily black carbon geometric mean exposures ranged from 0.1 to 2.3 μg/m3, with a median daily geometric mean of 0.3 μg/m3. The highest black carbon concentrations were measured on farmers who used or worked near diesel vehicles (geometric mean ranged from 0.5 μg/m3 while harvesting to 4.9 μg/m3 during animal work). Higher geometric means were found for near vs. far proximity to diesel-fueled vehicles and equipment (2.9 vs. 0.3 μg/m3). Indoor, bystander proximity to diesel-operated vehicles resulted in the highest geometric mean black carbon concentrations (18 μg/m3). Use of vehicles with open cabs had higher mean black carbon concentrations than closed cabs (2.1–3.2 vs. 0.4–0.9 μg/m3). In summary, our study provided evidence that farmers were frequently exposed to black carbon associated with diesel-related activities at levels above urban ambient concentrations in their daily work during harvest.

Black Carbon Exposure Characteristics in Diesel Engine Vehicle-related Jobs

“…Our results show that increased proximity to diesel engine exhaust sources and indoor work are the main determinants of BC exposure levels. This finding is supported by Stapleton et al (2018) and Sauvé et al (2020). They analyzed farming activity and reported that BC exposure levels increased when close to diesel-powered equipment indoors.…”

“…Farmers who used or worked near diesel vehicles were reported to be exposed to GMs of BC exposure ranging from 0.5 µg m -3 while harvesting to 4.9 µg m -3 during animal work. Higher GMs were found for increased proximity to diesel-fueled vehicles and equipment (2.9 vs. 0.3 µg m -3 ) (Stapleton et al, 2018). A 68% increase in BC concentration was predicted when working near diesel-powered vehicles compared to far proximity (Sauvé et al, 2020).…”

“…Several studies have reported an increased occupational exposure to BC in a large group of workers including municipal household garbage collectors (Lee et al, 2015), traffic police (Shakya et al, 2016), underground tunnel construction workers (Galea et al, 2016), farmers (Stapleton et al, 2018;Sauvé et al, 2020), subway workers (Choi et al, 2019) and toll operators (Shin et al, 2021). According to these studies, BC exposure levels were high when working with dieselpowered equipment indoors such as underground tunnels or subway.…”

Environmental Health Threats to Latino Migrant Farmworkers

“…Farmworkers are exposed to numerous air pollutants, including black carbon, particulate matter, carbon monoxide, nitrogen dioxide, sulfur dioxide, and diesel-related emissions from farm activities, such as tractor driving, maintenance and repair of machinery and equipment, and agricultural crop residue burning (122,134). These exposures increase the risk of adverse respiratory and cardiopulmonary outcomes among farmworkers, including lung cancer, wheeze, asthma, and chronic obstructive pulmonary disease (COPD) (63,122,134).…”

Correlation between Graphitic Carbon and Elemental Carbon in Diesel Particulate Matter in Workplace Atmospheres

“…Absorbance-based optical monitors, such as an Aethalometer, have been used for near-real time monitoring of black carbon (BC). , Correlation was found between the BC concentration obtained from the Aethalometer and EC concentration determined by NIOSH Method 5040. However, a workplace-specific conversion factor is required for more accurate EC estimates as light attenuation in this optical technique is influenced by the particle morphology, filter loading, varying refractive indices, and scattering by other sample components, and possible absorption of non-EC materials.…”