A predictive model for the home outdoor exposure to nitrogen dioxide

The aim of this study is to find and test a predictive model that could be suitable to estimate the outdoor NO(2) concentrations at individual level, by integrating ecological measurements recorded by local monitoring stations with individual information collected by a questionnaire. For this purpose, the data from the Italian centres of the European Community Respiratory Health Survey II (ECRHS II) has been used. Outdoor NO(2) concentrations were measured using NO(2) passive sampling tubes (PS-NO(2)), exposed outdoor for 14 days, between January 2001 and January 2003. Simultaneously, average NO(2) concentrations were collected from all the monitoring stations of the three centres (MS-NO(2)). Individual measurements carried out with passive samplers were compared with the corresponding NO(2) 2-week concentrations obtained as the average of all local (background and traffic) monitoring stations (MS-NO(2)). A multiple linear regression model was fitted to the data using the 2-week PS-NO(2) concentrations as the response variable and questionnaire information and MS-NO(2) concentrations as predictors. The model minimizing the root mean square error (RMSE), obtained from a ten-fold cross validation, was selected. The model with the best predictive ability included centre, season of the survey, MS-NO(2) concentrations, type and age of building, residential area and reported intensity of heavy-duty traffic and explained the 68.9% of the variance. The non-parametric correlation between PS-NO(2) and the concentrations estimated by the model is 0.81 (95% CI: 0.77-0.85). This study shows that over short periods (2 weeks) a good prediction of home outdoor exposure to NO(2) can be achieved by simply combining routinely collected ecological data with dwelling characteristics and self-reported intensity of heavy traffic. Further studies are needed to extend this prediction to long-term exposure.     

Carbon Dioxide Evolution and Moisture Evaporation During Roasting of Coffee Beans

ABSTRACT: Evolution of carbon dioxide and water vapor during roasting of coffee was followed in an isothermal high-temperature short-time and a low-temperature long-time roasting process. In addition, CO₂ release during storage of roasted beans was followed. CO₂ and water vapor concentration were assayed in the exhaust air by nondispersive infrared gas analysis. Although CO₂ evolution rates differed in the 2 processes, the final total amount of CO₂ released after 63 d of storage remained equal. CO₂ evolution and differentiation between evaporation of initial water and chemically formed water showed that chemical reactions leading to relevant amounts of CO₂ and water start at ap -proximately 180°C. A mass balance established on the present measurements was able to account fairly well for the gravimetrically measured roast loss.     

Cuticular Hydrocarbons of the Dampwood Termite, Zootermopsis nevadensis: Caste Differences and Role of Lipophorin in Transport of Hydrocarbons and Hydrocarbon Metabolites

The epicuticular and internal hydrocarbons (HC) from different castes of the dampwood termite Zootermopsis nevadensis were analyzed by gas chromatography–mass spectrometry. The epicuticular HC profiles of workers and alates contained large proportions of n-heneicosane (n-C21), 5-methylheneicosane (5-MeC21), and 5,17- and 5,15-dimethylheneicosane (5,17-, 5,15-diMeC21). Sixty-three HC peaks were identified as normal-, monomethyl-, dimethyl-, and trimethylalkanes up to 41 carbons long. The HC content of the internal tissues was significantly greater than on the epicuticle in all castes examined (2.8-fold in female alates, 5.7-fold in male alates, and 13.7-fold in workers). The hemolymph of all castes, including workers, soldiers, nymphs, and female and male alates, contained large amounts of HC and all hemolymph samples had nearly identical HC profiles. However, the hemolymph profile was remarkably different from the cuticular profile. KBr equilibrium gradient ultracentrifugation of worker hemolymph showed that all HC were associated with a high-density lipophorin (density of 1.12 ± 0.005 g/ml) consisting of two subunits, apolipophorin-I (220 kDa) and apolipophorin-II (82 kDa). After topical application of radiolabeled 3,11-dimethylnonacosane, a HC that is closely related to a native HC, all the internalized HC and radiolabeled lipid metabolites that were recovered from the hemolymph were associated with lipophorin. These findings are consistent with the hypothesis that lipophorin transports HC and some HC metabolites through the hemolymph from the sites of synthesis to the integument and from the integument to metabolic and excretory tissues. In many social insects, different castes have different relative proportions of the same HC and lipophorin appears to play an important role in regulation of the externalization and internalization of HC and, therefore, in the attainment of caste-specific chemical profiles.     

Intake fraction distributions for indoor VOC sources in five European cities

Distributions of intake fractions for indoor air emissions were estimated for five cities in the EXPOLIS study (Athens, Basel, Helsinki, Oxford, and Prague). Intake fractions are an expression of the mass of a pollutant that reaches a target compared with the mass emitted by a source. They facilitate direct comparisons of the relative impact of different sources on individual or population exposure and dose. The computation of the distributions was obtained through Monte Carlo simulations, based on distributions of residence volume, air exchange rates and time-activity data, calculated from the EXPOLIS database, as well as on distributions from the literature. Some approximations were made that are valid for persistent pollutants and continuous sources, such as emissions from building materials, pesticides, molds, as well as for certain non-continuous sources such as cooking or cleaning products. For these categories of sources, intake fractions are approximately independent of the actual indoor concentrations and irrespective of the source. Intake fractions in the five populations examined followed approximately lognormal distributions. The mean individual intake fractions exhibited some variability across cities, ranging from 1.5x10(-3) in Athens to 4.5x10(-3) in Helsinki. Intake fractions for all the people in a household followed similar distributions, with mean values ranging from 4.6x10(-3) in Athens to 11.8x10(-3) in Helsinki. This modest variability mostly reflects the differences in climates and consequent air-tightness of the buildings. The 95th percentile of the distributions were two to three times the mean values, indicating substantial homogeneity within each population as well. These results compare well with previous estimates for environmental tobacco smoke and cooking, and are two to three orders of magnitude larger than estimates for outdoor sources. PRACTICAL IMPLICATIONS: Emissions from indoor sources were estimated to be approximately 1000 times more likely to reach a human target than emissions from outdoor sources. Strategies to reduce exposure to indoor sources can only realistically focus on reducing the strength of the emissions.