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Med. Pr. 2005;56(3)

Exposure assesment to harmful agents in workplaces in sewage plant workers

Ocena narażenia pracowników oczyszczalni ścieków na czynniki szkodliwe występujące w miejscu pracy

Marcin Cyprowski1, Jadwiga Szarapińska-Kwaszewska2, Bożena Dudkiewicz2, Jan A. Krajewski1, Irena Szadkowska-Stańczyk1 1 Z Zakładu środowiskowych Zagrożeń Zdrowia Instytutu Medycyny Pracy im. prof. J. Nofera w Łodzi 2 Z Zakładu Mikrobiologii Farmaceutycznej Uniwersytetu Medycznego w Łodzi

Abstract

Background:The purpose of the study was to evaluate exposure to biological and chemical agents in a sewage treatment plant. Materials and Methods: Sampling was carried out in the summer and wintertime at the morning workshift. Ninety-nine sewage workers taking part in the study were divided into four occupational subgroups: mechanical treatment, biological treatment, sewage sludge treatment, and operation control workers. Exposure to: H₂S, SO₂, Pb, Cd, Cr³⁺, Cr6+, endotoxins, (1→3)-ß-D glucans, and microorganisms was evaluated with special identification of Gram-negative rods. Results: The concentrations of dust containing heavy metals and concentrations of gases from all stationsdid not exceed MAC values. Concentrations of endotoxins ranged from 0.08 to 223 ng/m³, and glucans from 0.00 to 163 ng/m³. The highest concentrations were found among sewage sludge treatment workers, in the summertime (geometric mean value = 37 ng/m³). In the winter, concentrations were almost ten times lower. Over sixty percent of all results exceeded the proposed reference value for airborne endotoxins (10 ng/m³). Concentrations of airborne bacteria in the sewage plant were at low level (10² cfu/m³), except the sludge lagoon and sludge concentration building, where the results exceeded the proposed reference value for mesophilic bacteria (10⁵ cfu/m³) śEnvironmentalś bacteria (Pseudomonas, Burkholderia, Shewanella) predominated in the samples. There were also found enterobacteria genus (Enterococcus, family Enterobacteriaceae) ś good indicators of hygienic cleanliness of the air. Conclusions: The study proved that the exposure varied and depended on the stage of sewage treatment. The sewage sludge treatment process was characterized by the highest emission of bioaerosols. All microorganisms found in the sewage plant belong to the second occupational risk group, under the ordinance of the Ministry of Health.

Key words

sewage treatment plant, occupational exposure, bioaerosols, endotoxins, (1→ 3)-β-D glucans