Personal NO2 exposures of preschool children in Helsinki

Weekly personal NO2 exposures of 246 children aged 3-6 years were measured with Palmes tubes during 13 weeks in winter and spring in 1991. Measurements were made in eight day-care centers in the downtown and suburban areas of Helsinki, Finland. At the same time, inside and outside NO2 concentration of the day-care centers and the ambient air fixed site measurements were conducted. Palmes tubes were found to be applicable for NO2 exposure measurements of preschool children, but rather high sample losses could be expected. The geometric mean of personal NO2 exposure levels of 13-week period was 26.5 micrograms/m3 in the downtown and 17.5 micrograms/m3 in the suburban area. Gas stove and smoking at home increased significantly personal exposure to NO2. The weekly population NO2 exposure correlated rather poorly with the fixed site ambient air NO2 levels (R2 = 0.37), but much better with the NO2 levels inside and outside the day-care centers (R2 = 0.88 and 0.86). In the suburban and downtown groups the between children variations in the NO2 exposures were only 14% and 28% of the total variations, which were dominated by the within child variation. Stationary measurements at the ambient air fixed sites and inside and outside the day-care centers explained the variation in personal exposures of the children well during the spring, but not during the winter. A regression model, where data from outside day-care center measurements, fixed ambient air monitors, residential area and home characteristics (i.e., gas stove, smoking inside at home, type of dwelling) were included, explained 32% of the personal NO2 exposure variation in winter and 67% in spring. In the absence of personal exposure measurements, both stationary measurements and questionnaire information are useful in estimating variations in personal exposures.     

Hygienic Aspects of Processing Oil Residues in Ventilation Ducts

The hygienic properties of two types of processing oils used in the manufacture of galvanised metal air ducts mere investigated. One of the oils was based on mineral oil and the other on vegetable oil. Evaporation of the oil emulsions from the galvanized metal surface was followed for ten months, after which the water-binding capacity of the residues was measured in increasing and decreasing RH at the range of 75-100%. The potential of processing oil residues to act as nutrients for fungi was tested with Penicillium brevi-compactum in the laboratory. The odour emission of oil residues was evaluated with the aid of a trained panel for eight months. After the ten months, the residue of mineral-oil- and vegetable-oil-based products was 60% and 79% of the original amount, respectively. Both oils were able to absorb water but desorption of the water from vegetable-oil-based products was delayed, thus increasing the risk of fungal growth. The residues of both oils provided sufficient nutrients for fungal growth. The odour emissions from the oil residues were high and that of vegetable oil tended also to increase. To attain high indoor air quality, duct manufacturing methods which do not leave residues should be developed.     

The relationship between measured moisture conditions and fungal concentrations in water-damaged building materials

We determined the moisture levels, relative humidity (RH) or moisture content (MC) of materials, and concentrations of culturable fungi, actinomycetes and total spores as well as a composition of fungal flora in 122 building material samples collected from 18 moisture problem buildings. The purpose of this work was to clarify if the is any correlation between the moisture parameters and microbial levels or generic composition depending on the type of materials and the time passed after a water damage. The results showed an agreement between the concentrations of total spores and culturable fungi for the wood, wood-based and gypsum board samples (r > 0.47). The concentrations of total spores and/or culturable fungi correlated with RH of materials particularly among the wood and insulation materials (r > 0.79), but not usually with MC (r < 0.45). For the samples collected from ongoing damage, there was a correlation between RH of materials and the concentrations of total spores and culturable fungi (r > 0.51), while such a relationship could not be observed for the samples taken from dry damage. A wide range of fungal species were found in the samples from ongoing damage, whereas Penicillia and in some cases yeasts dominated the fungal flora in the dry samples. This study indicates that fungal contamination can be evaluated on the basis of moisture measurements of constructions in ongoing damage, but the measurements are not solely adequate for estimation of possible microbial growth in dry damage.     

Antimicrobial and cytotoxic knotwood extracts and related pure compounds and their effects on food-associated microorganisms

Knotwood or bark extracts prepared from 30 species of hard and soft wood trees as well as selected pure compounds (lignans, stilbenes and flavonoids) were assayed for their antimicrobial activity against a battery of both gram positive and negative bacteria, yeasts, and filamentous fungi (Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Lactobacillus plantarum, Escherichia coli, Salmonella infantis, Pseudomonas fluorescens, Candida albicans, Saccharomyces cerevisiae, Aspergillus fumigatus and Penicillium brevicompactum). By far the most consistent antibacterial and antifungal properties were associated with extracts of Pinus species. These extracts showed also cytotoxicity against a mouse hepatoma cell line. Both antimicrobial and cytotoxic properties correlated with the stilbene content of the extracts. Purified stilbenes showed the most consistent antimicrobial and cytotoxic activities, while purified lignans had marginal effects, only. The results suggest that stilbenes account both for the antimicrobial and cytotoxic properties of Pinus knotwood extracts.