Reduction of microbial air pollution in waste sorting plants

Status:

completed 12/1995

Aims:

With the development of new strategies of waste management, a multitude of new workplaces with exposure to biological working agents were created. A typical example are waste sorting plants, where packaging waste is sorted manually. As the used packaging is often soiled with food and thus micro- organisms, microbial air concentrations are very high especially at points of extreme air movement. Exposure to high mould fungi and bacteria concentrations are likely to cause toxic and allergic diseases of the respiratory tract; it is therefore necessary to conduct workplace assessments to take appropriate protective measures. The project was aimed to determine workers' exposure to micro-organisms (especially to mould fungi) in the air of waste sorting plants and to investigate to which extent technical framework conditions may affect exposure positively (reduced microbial air concentration).

Activities/Methods:

The latest procedures for waste sorting plants are described, including plant engineering, process cycles, workplaces and other important parameters. Once a number of suitable plants is selected, the microbial air concentration (especially mould fungi) at the workplaces is determined by use of standardised, national measuring methods for microbiological agents. The measurement approach (parameters, strategy) is optimised. The efficiency of emission- reducing measures is evaluated. The aim is to develop a safety concept to minimise the risk of exposure.

Results:

The results of microbial air pollution measurements in waste sorting plants show that the concentration of mould fungi in the workplace air is particularly high. Consecutive investigations in 32 waste sorting plants revealed that average mould fungi concentrations came to 630,000 colony- forming units/m³ in sorting cabins, and to 1.500.000 colony- forming units /m³ in delivery areas. The results illustrate that there are already less expensive measures to reduce microbial pollution. The air quality in sorting cabins is clearly affected by the presence of a ventilation system which must, of course, be designed and installed carefully (controlled collection and fresh air supply). Efficient germ reduction can also be achieved by all kinds of measures which help reduce dust emission and dust spreading. A good hygiene and cleaning approach is equally efficient. At workplaces where such measures have a limited effect, other solutions must be found ( e.g. automatic opening of refuse collection bags). The results gathered in the context of these investigations were discussed against the background of occupational health and safety regulations for waste sorting plants. In conclusion, it was not only possible to use standardised measuring methods and optimise the measuring approach (parameters, strategy), but the project served also to gain basic knowledge which is important for the determination of workplace exposure to biological agents in general.

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