The influence of meteorological parameters on indoor and outdoor radon concentrations : a preliminary case study

In this study the influence of meteorology on indoor and outdoor radon concentrations in four different locations in a Mediterranean country have been studied. Indoor, daily radon concentrations were generally higher (0.2 – 85.0 Bq m-3) than outdoor daily concentrations (0.8 – 3.6 Bq m-3) in all locations studied with the exception of one that was built on pylons, thus reducing infiltration of radon from the ground. Indoor and outdoor meteorological parameters influence both the indoor and outdoor radon concentrations. In particular, outdoor wind speed and relative humidity show a negative correlation with both outdoor and indoor concentrations at all locations. Radon concentrations were also measured at two different levels of a terraced house (a common household type in Malta), in the basement and on ground floor. Results show that if the interconnecting door is left open, the radon in the basement infiltrates to the ground floor, increasing the average radon daily concentration in the living area by approximately 1.5 times.peer-reviewe

Evaluation of two street canyon air quality models using data from European cities

This paper presents a sensitivity analysis of the Operational Street Pollution Model (OSPM) and an evaluation of OSPM and the Assessing the Environment Of Locations In Urban Streets (AEOLTUS) model. Both models calculate airborne concentrations of exhaust gases emitted by motor vehicles within street canyons. They perform best when the street canyon aspect ratio is 1.0. OSPM and AEOLIUS have been evaluated using data collected over a two-year period (1 994- 95) in Jagtvej, Copenhagen, Denmark. Further evaluation of the models was carried out using data collected in Giittinger Strasse, Hannover (1994) and Schildhom Strasse, Berlin (1995), both in Germany. In all cases, model runs were carried out for carbon monoxide (CO). In the case of OSPM, two sets of newly proposed emission factors were used for the street canyons in Germany. In the calculation of these factors, the urban driving patterns and variations in the composition of the vehicle fleet according to the engine capacity were assumed as the most appropriate for the cases considered. Furthermore, parameters such as engine operating temperature and the use of catalytic converter were taken into account. Scatter plots of modelled against measured CO concentration yielded an average regression coefficient of 0.90 for the street canyons considered. With the newly proposed emission factors for Germany a lower regression coefficient was obtained. From similar scatter plots, the AEOLIUS model gave a regression coefficient of 0.86 for Jagtvej in 1994 and 0.78 for 1995. For Gottinger and Schildhorn Strasse, the regression coefficient obtained was 0.8 1.peer-reviewe

Evaluation of the cancer risk from PAHs by inhalation:Are current methods fit for purpose?

There is ample evidence from occupational studies that exposure to a mixture of Polycyclic Aromatic Hydrocarbons (PAHs) is causally associated with an increased incidence of lung cancers. In both occupational atmospheres and ambient air, PAHs are present as a mixture of many compounds, but the composition of the mixture in ambient air differs from that in the occupational atmosphere, and varies in time and space in ambient air. Estimates of cancer risk for PAH mixtures are based upon unit risks which derive from extrapolation of occupational exposure data or animal model data, and in the case of the WHO use one compound, benzo[a]pyrene as a marker for the entire mixture, irrespective of composition. The U.S. EPA has used an animal exposure study to derive a unit risk for inhalation exposure to benzo[a]pyrene alone, and there have been a number of rankings of relative carcinogenic potency for other PAHs which many studies have used to calculate a cancer risk from the PAHs mixture, frequently incorrectly by adding the estimated relative risks of individual compounds, and applying the total “B[a]P equivalent” to the WHO unit risk, which already applies to the entire mixture. Such studies are often based upon data solely for the historic US EPA group of 16 compounds which do not include many of the apparently more potent carcinogens. There are no data for human cancer risk of individual PAHs, and conflicting evidence of additivity of PAH carcinogenicity in mixtures. This paper finds large divergences between risk estimates deriving from the WHO and U.S. EPA methods, as well as considerable sensitivity to the mixture composition, and assumed PAH relative potencies. Of the two methods, the WHO approach appears more likely to provide reliable risk estimates, but recently proposed mixture-based approaches using in vitro toxicity data may offer some advantages.peer-reviewe

The impact of school environment on children’s respiratory health

The study was done as part of the European Union SINPHONIE Study commissioned by DG SANCO. The authors received some funding from SINPHONIE (European Commission service contract of the DG Sanco).Abstract Background/Aims: School indoor air quality is important because children spend most of their time outside home within the school environment. This study aimed to investigate the school environment and its impact on the respiratory health of the children. Methods: A total of 191 pupils in the 9- to 11-year age group were selected from 5 primary state schools. Validated school and health questionnaires, spirometry, acoustic rhinometry, nasal lavage, urine for environmental tobacco smoke biomarkers and traffic counts were used. Results: Cumulative (32.98%) and current wheezing (17.8%) were in keeping with the International Study of Asthma and Allergies in Childhood Malta data. Southern schools had the highest prevalence of current wheezers (OR 3.77; p = 0.012), rhinoconjunctivitis (OR 3.59; p = 0.003) and nasal eosinophilic cationic protein levels (p < 0.001). Small openable window areas increased rhinitic symptoms (OR 3.14; p = 0.016). Classes facing roads had increased current wheezers (OR 2.27; p = 0.03) and exhaled carbon monoxide (eCO) levels (p < 0.001). Current wheezing was significantly associated with the number of light and heavy vehicles passing near the school (p < 0.001). The presence of smokers at home was significantly associated with urinary cotinine and 3HC (p < 0.001). Proximity to power plants increased the current wheezers (OR 5.89; p = 0.001) who had impaired spirometry (p = 0.003). Asthma symptoms (OR 5.25; p = 0.001) and elevated eCO levels (p < 0.001) were associated with fuel storage facilities near schools. The accumulation of dust on flat surfaces within classrooms was related to wheezing (OR 5.23; p = 0.001). Conclusions: The school environment had a direct impact on the respiratory health of children, with several factors having a direct impact on the children's health.peer-reviewe

COVID-19-related changes in NO2 and O3 concentrations and associated health effects in Malta

The start of 2020 has been characterized by emission reductions in various countries across the globe following the implementation of different lock-down measures to control the transmission of the SARS-CoV-2 (COVID-19). Consequently, these reductions influenced the air quality globally. In this study, we focus on daily nitrogen dioxide (NO2) as well as ozone (O3) concentrationsmeasured across theMaltese Islands between January and mid-October 2020. Changes in air quality are generally difficult to detect due to the complex composition and interactions occurring within the atmosphere. To quantify changes in NO2 and O3 concentrations during the COVID-19 period, we use a random forest machine learning algorithm to determine a business as usual counterfactual scenario. Results highlight a decrease in monthly mean NO2 concentrations by up to 54% in the traffic site of Msida ( 21 μg m−3). In contrast, the monthly mean O3 concentrations during the COVID-19 months are up to 61% higher compared to a business as usual scenario in Msida ( 28 μg m−3). In this study, we also estimate the differences in attributable fraction (AF) associated with short-term exposure to NO2 and O3 concentrations. In Msida, the AF is up to 0.9% lower and 0.8% higher for measured NO2 and O3 concentrations, respectively. Our results highlight the favorable effects of decreasing traffic-related emissions on NO2 concentrations however, we also note increases in other pollutants for example O3 concentrations which especially in the short-term can lead to various adverse health effects.peer-reviewe

Comparison of machine learning approaches with a general linear model to predict personal exposure to benzene

Machine learning techniques (MLTs) offer great power in analyzing complex data sets and have not previously been applied to non-occupational pollutant exposure. MLT models that can predict personal exposure to benzene have been developed and compared with a standard model using a linear regression approach (GLM). The models were tested against independent data sets obtained from three personal exposure measurement campaigns. A correlation-based feature subset (CFS) selection algorithm identified a reduced attribute set, with common attributes grouped under the use of paints in homes, upholstery materials, space heating, and environmental tobacco smoke as the attributes suitable to predict the personal exposure to benzene. Personal exposure was categorized as low, medium, and high, and for big data sets, both the GLM and MLTs show high variability in performance to correctly classify greater than 90 percentile concentrations, but the MLT models have a higher score when accounting for divergence of incorrectly classified cases. Overall, the MLTs perform at least as well as the GLM and avoid the need to input microenvironment concentrations

Model Development and Validation of Personal Exposure to Volatile Organic Compound Concentrations

Background: Direct measurement of exposure to volatile organic compounds (VOCs) via personal monitoring is the most accurate exposure assessment method available. However, its wide-scale application to evaluating exposures at the population level is prohibitive in terms of both cost and time. Consequently, indirect measurements via a combination of microenvironment concentrations and personal activity diaries represent a potentially useful alternative. Objective: The aim of this study was to optimize a model of personal exposures (PEs) based on microenvironment concentrations and time/activity diaries and to compare modeled with measured exposures in an independent data set. Materials: VOC PEs and a range of microenvironment concentrations were collected with active samplers and sorbent tubes. Data were supplemented with information collected through questionnaires. Seven models were tested to predict PE to VOCs in 75% (n = 370) of the measured PE data set, whereas the other 25% (n = 120) was used for validation purposes. Results: The best model able to predict PE with independence of measurements was based upon stratified microenvironment concentrations, lifestyle factors, and individual-level activities. The proposed model accounts for 40–85% of the variance for individual VOCs and was validated for almost all VOCs, showing normalized mean bias and mean fractional bias below 25% and predicting 60% of the values within a factor of 2. Conclusions: The models proposed identify the most important non-weather-related variables for VOC exposures; highlight the effect of personal activities, use of solvents, and exposure to environmental tobacco smoke on PE levels; and may assist in the development of specific models for other locations.peer-reviewe

Tobacco-specific and combustion pollutants in settled house dust in Malta

Aim: Most of the carcinogenic pollutants coming from tobacco smoking or other combustion processes tend to accumulate in settled house dust (SHD) over time. This study evaluated the load of these pollutants in smokers and non-smokers’ houses from relatively fresh SHD collected in five different districts on the island of Malta. Methods: An improved, efficient extraction method to obtain three fractions from a 200 mg of SHD was developed. It was validated for the analysis of nicotine and polycyclic aromatic hydrocarbons (PAH) by GCMS/ MS and nicotelline and TSNA by LC-MS/MS. Kruskal-Wallis H tests were used to evaluate differences across districts, while a Mann-Whitney U test was used to check differences between smokers and non-smokers’ houses. Diagnostic ratios were used to evaluate the carcinogenicity of PAH in SHD in Malta. Results: For all analytes, no statistical difference was observed across different districts, but, in smokers’ houses, 97.9% of the total concentration of all target analytes found in SHD is nicotine, 0.1% is TSNA, and 2.0% is PAH. In non-smokers’ houses, nicotine represents 16.8% of the load, while 0.4% and 82.8% are TSNA and PAH, respectively. The carcinogenicity of the PAH mixture in Maltese SHD, expressed as the mean benzo(a)pyrene equivalent (BaPeq) is 371 ng/g. Conclusion: Indoor activities, ventilation practices, and infiltration of outdoor pollutants contribute to a complex SHD composition. Although the BaPeq is on the lower end of carcinogenicity, the effects of a mixture including tobacco-related potent carcinogens in SHD are largely unknown. In view of indoor, continuous exposure to SHD through several pathways, further research is warranted.peer-reviewe

Validation of an optimised microwave-assisted acid digestion method for trace and ultra-trace elements in indoor PM2.5 by ICP-MS analysis

Three microwave-assisted digestion procedures, followed by analysis of digestates employing inductively coupled mass spectrometry (ICP-MS) were evaluated for use in the determination of elements at trace and ultra-trace levels in PM2.5 samples. Digestion procedure 1 used 2.5 mL HNO3 (65%) at 200 ◦C. Procedure 2, consisted of a two-stage digestion step at 200 ◦C with 2.5 mL HNO3 (65%) and 3 μL HF (48%) followed by 24 μL H3BO3 (5%). A 10-fold increase in the amounts of HF and H3BO3 was used for procedure 3. The addition of HF/H3BO3 was carried out to aid the dissolution of silicate matrices and refractory compounds. The digestions were carried out using PTFE ultra-trace inserts which increased the sample throughput threefold. The addition of small quantities of HF resulted in the effective solubilisation of Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Cd, Sb and Pb. The optimal method using HNO3/HF/H3BO3 digestion as in procedure 3 showed recovery efficiency greater than 70% for all elements. The validated method was applied to quantify the elemental content of indoor and outdoor PM2.5 (with samples <0.5 mg) at an urban background site in Malta.peer-reviewe