Effects of waste treatment technique and quality of waste on bioaerosols in Finnish waste treatment plants

Abstract

Outi Tolvanen selvitti tutkimuksessaan mikrobi-, endotoksiini- ja pölypitoisuuksia suomalaisilla jätteenkäsittelylaitoksilla. Tolvanen tutki, onko jätteiden tehostunut syntypistelajittelu ja jätteiden käsittely suljetuissa laitoksissa vähentänyt bioaerosolien ja pölyn aiheuttamia työhygieenisiä ongelmia. Kohonneiden mikrobipitoisuuksien on aikaisemmissa tutkimuksissa havaittu aiheuttavan jätteitä työssään käsitteleville henkilöille erilaisia oireita, kuten pahoinvointia, päänsärkyä, kuumeilua sekä allergiaa ja astmaa.

The last fifteen years have seen immense changes in waste treatment in Finland. The number of landfill sites has been reduced and new waste treatment plants have been constructed; source separation of the various waste fractions has been become increasingly effective. At the same time, considerable attention has been paid to environmental factors such as odour problems. Another important factor at waste treatment plants is the working conditions of employees. Earlier, there were numerous problems with occupational hygiene in sewage treatment plants and landfills. The present study was undertaken to determine whether serious problems with bioaerosols still exist now that there are new waste treatment techniques and waste is sorted. The concentrations of dust, microbes and endotoxins were investigated at one windrow composting site in 1993-1994 and at eight waste treatment plants in 1998-2003. The best environment in regard to occupational hygiene was the combined drum and tunnel composting plant in Heinola. The most problematic area in the plant was the storage room (tunnel) for compost, but the concentrations of bioaerosols were low even there. At the composting plant in Hyvinkää, where the same kind of technique was in use, there were problems with bioaerosols in all working areas investigated. The same problems were encountered in dirty working areas in a drum composting plant in Oulu; in the control room number of bioaerosols was low. Conditions were worst in the dry waste treatment plant in Tampere, where viable microbes were a particular problem in the processing hall. As well, the concentrations of dust and endotoxin were occasionally increased to a level harmful to human health. The dry waste was most affected with microbes, while the treatment of wood waste caused problems with dust. In the other plants of the study, sorting and crushing of waste caused the highest concentrations of bioaerosols. The two most common air-borne fungi at every plant were Penicillium spp. and Aspergillus spp. Both fungi may cause allergy and produce harmful metabolic compounds. The aerodynamic diameter of most of the viable microbes at every plant was < 5 mm. These microbes may penetrate deep to alveoli and represent a health hazard.This study shows that the movement of waste treatment from open fields to indoor facilities has not reduced all problems of occupational hygiene. In particular, the number of mesophilic fungi was significantly higher at indoor facilities than in the open composting field. For the determination of microbial numbers, the impactor gives better (higher) results for viable microbes than the CAMNEA method. There is a problem with the impactor, however: if the concentrations of viable microbes are very high, at a level > 105 cfu/m3, the sampling time has to be very short, just 30 s to 1 min, and then the representativenes of the sample may suffer. Using an impactor is easy, however, and the method is cheaper than the Camnea method. There are also some problems with dust sampling, especially in winter, when static electricity interferes, sometimes even giving rise to negative results