Relationship between concentrations of microbiological agents in the air of agricultural settings and occurrence of work-related symptoms in exposed persons

Department of Pneumonology, Oncology and Allergology, Medical University of Lublin, Lublin, Poland
Department of Biological Health Hazards and Parasitology, Institute of Rural Health, Lublin, Poland
Ann Agric Environ Med 2015;22(3):473–477
For assessment of the dose-response relationship between concentrations of microbial agents in the air of various agricultural settings and occurrence of work-related symptoms in exposed workers, a meta-analysis of the results obtained in 1994–2007 on the territory of eastern Poland was performed. The studies on the airborne concentrations of total culturable microorganisms, mesophilic bacteria, Gram-negative bacteria, thermophilic actinomycetes, fungi, and bacterial endotoxins, as well as on the frequency of work-related respiratory and general symptoms in the exposed workers, were carried out at grain, thyme, valerian, flax, and hop handling on farms, in cow barns, piggeries, horse stables and in a modern hatchery. The airborne concentrations of the total microorganisms were in the range of 9.2–1236.5 × 10[sup]3[/sup] CFU/m[sup]3[/sup] , of the total mesophilic bacteria 3.5–1225.8 × 10[sup]3[/sup] CFU/m[sup]3[/sup] , of Gram-negative bacteria 0.0- 46.2 × 10[sup]3[/sup] CFU/m[sup]3[/sup] , of thermophilic actinomycetes 0.0–7.1 × 10[sup]3[/sup] CFU/m[sup]3[/sup] , of fungi 2.1–77.9 × 10[sup]3[/sup] CFU/m[sup]3[/sup] , and of bacterial endotoxin 0.00925–429.55 µg/m[sup]3[/sup] . The frequency of work-related symptoms ranged between 21.7–63.8%. In a meta-analysis for assessment of the correlations between the log-transformed concentrations of airborne microbial agents and the occurrence of work-related symptoms, the multiple regression test was applied. Statistically significant correlations were found between the occurrence of work-related symptoms and the concentration of total airborne microorganisms (R=0.748555; P=0.020317), mesophilic bacteria (R=0.7573; P=0.029548), Gram-negative bacteria (R=0.835938; P=0.019129), and endotoxins (R=0.705356; P=0.03378). The correlations between the concentrations of thermophilic actinomycetes and fungi, on one side, and frequency of work-related symptoms on the other, did not attain the threshold of significance (P=0.087049 and P=0.062963, respectively). Results of the meta-analysis confirm harmful health effects of the total airborne microorganisms, total airborne mesophilic bacteria, airborne Gram-negative bacteria, and airborne bacterial endotoxin on the occupationally-exposed agricultural workers, and indicate a need for the establishment of internationally recognized occupational exposure limits for these microbial agents.
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