Occupational exposure and indoor air quality monitoring in a composting facility

The objective of this study was to investigate indoor air quality in a completely covered enclosure used for the aerobic composting of organic wastes originating from vegetable, fruit, and garden refuse. Samples of gases and vapors were taken in the ventilation exhaust ducts. Volatile organic compounds (VOCs) were collected on Tenax absorbent; after thermal desorption they were analyzed by gas chromatography/mass spectrometry. Hydrogen sulfide was determined using Dräger test tubes. Microbial samplings were conducted on four sites inside the hall. Microbes were collected using a modified Anderson high-volume sampler, consisting of two impactor stages. Results indicate that the concentrations of VOCs were rather low; only the limonene level was elevated, but it was still well below the current Dutch provisional threshold limit value. Hydrogen sulfide levels found were also far less than the Dutch threshold limit value. Both total bacteria and gram-negative bacterial counts exceeded the provisional Dutch guideline of 10,000 cfu/m3 for indoor air in the work environment. Furthermore, the number of fungi, for the larger part consisting of the genera Aspergillus and Penicillium, which are known to cause respiratory tract disorders, approached the hazardous exposure level.