Pertti Pasanen

Indoor aerosols: from personal exposure to risk assessment

Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10-30% of the total burden of disease from particulate matter exposure was due to indoor-generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor-generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control.

Significance of air humidity and air velocity for fungal spore release into the air

Abstract Our previous field studies have shown that the presence of molds in buildings does not necessarily mean elevated airborne spore counts. Therefore, we investigated the release of fungal spores from cultures of Aspergillus fumigatus, Penicillium sp. and Cladosporium sp. at different air velocities and air humidities. Spores of A. fumigatus and Penicillium sp. were released from conidiophores already at air velocity of 0.5 ms −1 , whereas Cladosporium spores required at least a velocity of 1.0 ms −1 . Airborne spore counts of A. fumigatus and Penicillium sp. were usually higher in dry than moist air, being minimal at relative humidities (r.h.) above 70%, while the effect of r.h. on the release of Cladosporium sp. was ambivalent. The geometric mean diameter of released spores increased when the r.h. exceeded a certain level which depends on fungal genus. Thus, spores of all three fungi were hygroscopic but the hygroscopicity of various spores appeared at different r.h.-ranges. This study indicates that spore release is controlled by external factors and depends on fungal genus which can be one reason for considerable variation of airborne spore counts in buildings with mold problems.

Airway Exposure to Silica-Coated TiO2 Nanoparticles Induces Pulmonary Neutrophilia in Mice

The importance of nanotechnologies and engineered nanoparticles has grown rapidly. It is therefore crucial to acquire up-to-date knowledge of the possible harmful health effects of these materials. Since a multitude of different types of nanosized titanium dioxide (TiO(2)) particles are used in industry, we explored their inflammatory potential using mouse and cell models. BALB/c mice were exposed by inhalation for 2 h, 2 h on 4 consecutive days, or 2 h on 4 consecutive days for 4 weeks to several commercial TiO(2) nanoparticles, SiO(2) nanoparticles, and to nanosized TiO(2) generated in a gas-to-particle conversion process at 10 mg/m(3). In addition, effects of in vitro exposure of human macrophages and fibroblasts (MRC-9) to the different particles were assessed. SiO(2)-coated rutile TiO(2) nanoparticles (cnTiO(2)) was the only sample tested that elicited clear-cut pulmonary neutrophilia. Uncoated rutile and anatase as well as nanosized SiO(2) did not induce significant inflammation. Pulmonary neutrophilia was accompanied by increased expression of tumor necrosis factor-alpha (TNF-alpha) and neutrophil-attracting chemokine CXCL1 in the lung tissue. TiO(2) particles accumulated almost exclusively in the alveolar macrophages. In vitro exposure of murine and human macrophages to cnTiO(2) elicited significant induction of TNF-alpha and neutrophil-attracting chemokines. Stimulation of human fibroblasts with cnTiO(2)-activated macrophage supernatant induced high expression of neutrophil-attracting chemokines, CXCL1 and CXCL8. Interestingly, the level of lung inflammation could not be explained by the surface area of the particles, their primary or agglomerate particle size, or radical formation capacity but is rather explained by the surface coating. Our findings emphasize that it is vitally important to take into account in the risk assessment that alterations of nanoparticles, e.g., by surface coating, may drastically change their toxicological potential.

Comparing the VOC emissions between air-dried and heat-treated Scots pine wood

The emissions of volatile organic compounds (VOCs) from air-dried Scots pine wood and from heat-treated Scots pine wood were compared with GC-MS analysis. Air-dried wood blocks released about 8 times more total VOCs than heat-treated (24 h at 230°C) ones. Terpenes were clearly the main compound group in the air-dried wood samples, whereas aldehydes and carboxylic acids and their esters dominated in the heat-treated wood samples. Only 14 compounds out of 41 identified individual compounds were found in both wood samples indicating considerable changes in VOC emission profile during heat-treatment process. Of individual compounds α-pinene, 3-carene and hexanal were the most abundant ones in the air-dried wood. By contrast, in the heat-treated wood 2-furancarboxaldehyde, acetic acid and 2-propanone were the major compounds of VOC emission. Current emission results reveal that significant chemical changes have occurred, and volatile monoterpenes and other low-molecular-weight compounds have evaporated from the wood during the heat-treatment process when compared to air-dried wood. Major chemical changes detected in VOC emissions are explained by the thermal degradation and oxidation of main constituents in wood. The results suggest that if heat-treated wood is used in interior carpentry, emissions of monoterpenes are reduced compared to air-dried wood, but some irritating compounds might be released into indoor air.

Critical aspects on the significance of microbial volatile metabolites as indoor air pollutants

Abstract The effect of microbial growth in building materials on airborne levels of volatile organic compounds (VOCs) was demonstrated by theoretically calculating indoor air concentrations of selected VOCs for rooms with and without microbial contamination. The recommended indoor air level for individual VOCs was also estimated on the basis of their sensory irritation potency. Furthermore, the irritation potency for the mixtures of certain compounds (microbial volatile metabolites, MVOCs) at airborne concentrations measured in problem buildings was evaluated. The theoretical airborne concentrations of certain compounds, which are generally regarded as MVOCs, were estimated to be only about 1% higher in the biocontaminated rooms than in those with moist sterile materials. In fact, no individual VOCs indicated exclusively microbial contamination, but they could also be emitted even from sterile, moist constructions. Exposure to mixtures of the selected non-reactive VOCs at the theoretical airborne concentrations would not result in sensory irritation in humans, and, thus, microbial growth in constructions should not increase the probability of irritating symptoms considerably. The data on MVOC concentrations measured in some problem buildings also supported this idea. Irritation would be expected when the airborne concentrations of single non-reactive compounds approach a level of hundreds of μg/m3 or mg/m3.

Volatile organic metabolites associated with some toxic fungi and their mycotoxins

A toxigenic strain of Fusarium sporotrichioides Sherbakoff was cultivated on straw, wheat and oat grains at a relative humidity of air (RH) of 84–100% for 17 days. Likewise, toxigenic and non-toxigenic strains of Penicillium verrucosum Dierckx were cultured on oat grain, aspen wood and wallpaper at RH 78–98% for 26 days. During the incubation, air samples were collected from the incubation chambers into Tenax TA adsorbent tubes every second day, and 12 microbial volatile organic compounds (MVOC) were identified from the air samples by thermal desorption–gas chromatography. The main MVOC included oct-1-en-3-ol, 3-methylbutan-2-ol, octan-1-ol, octan-3-ol, octan-3-one, hexan-2-one, heptan-2-one, α-pinene, and limonene. Especially ketones were formed in the grain cultures, possibly because of the high lipid content of grain. A relationship between the synthesis of mycotoxins and the relative proportion of different MVOC groups was detected, probably resulting from similar metabolic pathways. The production of volatile terpenes seemed to be linked to the formation of trichothecenes in the F. sporotrichioides cultures, and the P. verrucosum strain that is capable of synthesizing ochratoxin showed an accelerated production of volatile ketones compared with the ketone production of the non-toxigenic strain.

Microbial growth and metabolism in house dust

Microbial growth and production of carbon dioxide (CO2) and microbial volatile organic compounds (MVOC) were investigated in house dust. According to CO2 measurements, the metabolic activity increased after 11 days at 84–86% air relative humidity (RH) and after 3 days at 96–98% RH. Within 25 days, the concentration of fungal spores in house dust increased to about 45-fold at 84–86% RH resulting mainly from the growth of Aspergillus, Eurotium and Penicillium. At 96–98% RH, the proliferations were on average 1370- and 240-fold for fungi and bacteria, respectively. The dominating fungal genera were Aspergillus and Penicillium. The MVOC composition revealed that microbes can utilize, for example, fatty acids and possibly aldehydes as carbon source resulting in the production of MVOC such as methyl ketones and alcohols. The main MVOC produced by microbes in house dust were 2-pentanone, 2-hexanone, 2-heptanone, limonene, 2-methylfuran, formaldehyde, acrolein and nonanal. Also, 3-octanone, 2-ethyl-1-hexanol, 1-octen-3-ol, 3-methyl-1-butanol, 3-methyl-2-butanol, camphene and α-pinene can be considered to derive from microbial metabolism to some extent.

Seasonal and diurnal variation in formaldehyde and acetaldehyde concentrations along a highway in Eastern Finland

Abstract In this study the concentrations of the most important carbonyl compounds, formaldehyde and acetaldehyde, are measured in a highway environment in spring, summer and winter. Measurements were carried out in May, July and January along a two-lane highway, with daily traffic density 27 500 vehicles. Four sampling points were selected: (1) one from east and (2) west sides of the highway, (3) one at the central reservation of the highway and (4) one background site. The formaldehyde and acetaldehyde concentrations measured at both sides of a two-lane highway and at the central reservation suggest that the motor vehicle emissions are the source of these compounds throughout the year. The concentrations were, however, significantly lower at the roadsides than at the central reservation, especially in July. This could indicate rapid dilution of these compounds in the air. It is also possible that the vegetation along the roadside in summer may play a role as a sink or as a biogenic source for these compounds. The concentrations measured along the roadside in this study are comparable to those measured in polluted urban areas. The diurnal variation showed significant decrease of formaldehyde and acetaldehyde concentrations in the night indicating a decrease in primary source, i.e. traffic emissions. The seasonal variation was great as well, concentrations being lower in winter time, indicating lower secondary production of aldehydes. The formaldehyde and acetaldehyde effects on plants remains to be studied, since the formaldehyde and acetaldehyde pose a noteworthy risk to the vegetation exposed.

Personal Exposure Levels and Microenvironmental Concentrations of Formaldehyde and Acetaldehyde in the Helsinki Metropolitan Area, Finland

ABSTRACT Personal 48-hr exposures to formaldehyde and acetaldehyde of 15 randomly selected participants were measured during the summer/autumn of 1997 using Sep-Pak DNPH-Silica cartridges as a part of the EXPOLIS study in Helsinki, Finland. In addition to personal exposures, simultaneous measurements of microenvironmental concentrations were conducted at each participants residence (indoor and outdoor) and workplace. Mean personal exposure levels were 21.4 ppb for formaldehyde and 7.9 ppb for ac-etaldehyde. Personal exposures were systematically lower than indoor residential concentrations for both compounds, and ambient air concentrations were lower than both indoor residential concentrations and personal exposure levels. Mean workplace concentrations of both compounds were lower than mean indoor residential concentrations. Correlation between personal exposures and indoor residential concentrations was statistically significant for both compounds. This indicated that indoor residential concentrations of formaldehyde and acetaldehyde are a better estimate of personal exposures than are concentrations in ambient air. In addition, a time-weighted exposure model did not improve the estimation of personal exposures above that obtained using indoor residential concentrations as a surrogate for personal exposures. Correlation between formaldehyde and acetal-dehyde was statistically significant in outdoor microen-vironments, suggesting that both compounds have similar sources and sinks in ambient urban air.

Growth and volatile metabolite production of Aspergillus versicolor in house dust

Abstract The ability of A. versicolor to grow and produce volatile metabolites, carbon dioxide, and microbial volatile organic compounds (MVOC) in house dust, was investigated. First, signs of metabolic activity were detected after 7 d at relative humidity (RH) of air of 84–86% and after 2 d at RH of 96–98%. Within four weeks, the concentration of A. versicolor spores increased almost 100 fold at the lower RH and over 600 fold at the higher RH. However, after the fast rising at the beginning of the incubation, CO 2 concentration became steady probably because of the depletion of favourable carbon sources. MVOC were analyzed by gas chromatography with thermal desorption and mass selective detector and high pressure liquid chromatography. The results revealed that A. versicolor can utilize various hydrocarbons and fatty acids in house dust. Some MVOC were also formed as a result of the biosynthesis of amino acids. The main MVOC were 2-ethyl-1-hexanol, 1-octen-3-ol, 3-octanone, 2-heptanone, 2-pentanone, 2-hexanone, and 2-methylfuran. The last three compounds have not been presented earlier as volatile metabolites of this fungus.