A Task-Specific Algorithm to Estimate Occupational (1→3)-β-D-glucan Exposure for Farmers in the Biomarkers of Exposure and Effect in Agriculture Study

Abstract

Objectives Farmers may be exposed to glucans (a cell component of molds) through a variety of tasks. The magnitude of exposure depends on each farmer’s activities and their duration. We developed a task-specific algorithm to estimate glucan exposure that combines measurements of (1→3)-β-D-glucan with questionnaire responses from farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study. Methods To develop the algorithm, we first derived task-based geometric means (GMs) of glucan exposure for farming tasks using inhalable personal air sampling data from a prior air monitoring study in a subset of 32 BEEA farmers. Next, these task-specific GMs were multiplied by subject-reported activity frequencies for three time windows (the past 30 days, past 7 days, and past 1 day) to obtain subject-, task-, and time window-specific glucan scores. These were summed together to obtain a total glucan score for each subject and time window. We examined the within- and between-task correlation in glucan scores for different time frames. Additionally, we assessed the algorithm for the ‘past 1 day’ time window using full-shift concentrations from the 32 farmers who participated in air monitoring the day prior to an interview using multilevel statistical models to compare the measured glucan concentration with algorithm glucan scores. Results We focused on the five highest exposed tasks: poultry confinement (300 ng/m3), swine confinement (300 ng/m3), clean grain bins (200 ng/m3), grind feed (100 ng/m3), and stored seed or grain (50 ng/m3); the remaining tasks were <50 ng/m3 and had similar concentrations to each other. Overall, 67% of the participants reported at least one of these tasks. The most prevalent task was stored seed or grain (64%). The highest median glucan scores were observed for poultry confinement and swine confinement; these tasks were reported by 2% and 8% of the participants, respectively. The correlation between scores for the same task but different time windows was high for swine confinement and poultry confinement, but low for clean grain bins. Task-specific scores had low correlation with other tasks. Prior day glucan concentration was associated with the total glucan ‘past 1 day’ score and with swine confinement and clean grain bin task scores. Conclusions This study provides insight into the variability and key sources of glucan exposure in a US farming population. It also provides a framework for better glucan exposure assessment in epidemiologic studies and is a crucial starting point for evaluating health risks associated with glucans in future epidemiologic evaluations of this population.

Fungal bioaerosols as an occupational hazard

“…Historically, respiratory diseases associated with fungi in industrial workplaces were generally limited to areas where wood dusts, animal confinement and grain dusts were handled [12,13]. Exposures in these environments include grain particles, endotoxin, fungal allergens and beta 1,3 D glucan, that is mould glucan [14 ▪ ,15]. Over the decades, the American Conference of Government Industrial Hygienists (ACGIH) reduced the TLV for grain dust to the current level of 4 mg/m 3 , which is applied in both the USA and Canada [16].…”

An algorithm for quantitatively estimating occupational endotoxin exposure in the biomarkers of exposure and effect in agriculture study: II. Application to the study population

“…A task‐specific approach was necessary, as farmers vary in their activities (and their durations) depending on the types of crops and/or animals that they raise. Several task‐specific or source‐specific assessments have been conducted for other exposures in epidemiologic study populations, including (1 → 3)‐β‐ d ‐glucan for the BEEA Study, 15 and occupational lead 16 and benzene 17 exposure for other population‐based studies. These assessments all used a similar framework: task/source‐specific intensity estimates are multiplied by subject‐specific activity durations extracted from questionnaire responses.…”

“…This framework has helped identify contrast in exposure among study participants that can be used to evaluate exposure‐response associations in epidemiologic studies. For example, a contrast ratio (75th percentile divided by 25th percentile of the exposure metric) of 41 was found in the “past 30 day” glucan metric among participants who conducted at least one of five glucan‐exposed tasks, 15 a contrast ratio of 4−9 (depending on metric) was found among benzene‐exposed subjects in a case‐control study of non‐Hodgkin lymphoma, 17 and a contrast ratio of 10 was found among lead exposed‐subjects in a case‐control study of renal cell carcinoma 16 …”

“…In this paper, we describe the development and application of a quantitative endotoxin algorithm for the BEEA Study participants. The algorithm was developed to estimate endotoxin exposure for 13 tasks (five in common with the aforementioned glucan assessment 15 ) during four time windows, reflecting agricultural activities conducted in the past day, week, month, and year. A crucial first step was to derive task‐specific estimates based on published endotoxin data for each of the 13 tasks, which was described in detail in a companion paper 18 .…”

“…Several task-specific or source-specific assessments have been conducted for other exposures in epidemiologic study populations, including (1 → 3)-β-D-glucan for the BEEA Study, 15 and occupational lead 16 and benzene 17 exposure for other population-based studies.…”