A. G. Paliatsos

Acute effects of air pollution on pediatric asthma exacerbation: Evidence of association and effect modification

We investigated the short-term effects of particulate matter with aerodynamic diameter <10 μg/m(3) (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)) and ozone (O(3)) on pediatric asthma emergency admissions in Athens, Greece over the period 2001-2004. We explored effect modification patterns by season, sex, age and by the presence of desert dust transported mainly from the Sahara area. We used daily time-series data provided by the childrens hospitals and the fixed monitoring stations. The associations were investigated using Poisson regression models controlling for seasonality, weather, influenza episodes, day of the week and holiday effects. A 10 μg/m(3) increase in PM(10) was associated with a 2.54% increase (95% confidence interval (CI): 0.06%, 5.08%) in the number of pediatric asthma hospital admissions, while the same increase in SO(2) was associated with a 5.98% (95% CI: 0.88%, 11.33%) increase. O(3) was associated with a statistically significant increase in asthma admissions among older children in the summer. Our findings provide limited evidence of an association between NO(2) exposure and asthma exacerbation. Statistically significant PM(10) effects were higher during winter and during desert dust days, while SO(2) effects occurred mainly during spring. Our study confirms previously reported PM(10) effects on emergency hospital admissions for pediatric asthma and further provides evidence of stronger effects during desert dust days. We additionally report severe effects of SO(2), even at todays low concentration levels.

Forecasting peak pollutant levels from meteorological variables

The main objective of this paper is to present analytical models relating maximum pollutant concentrations in urban areas with meteorological and other variables. The analysis is based on measurements from Greater Athens Area and is restricted in only one pollutant of special interest, namely N02. The meteorological variables, used in analytical modeling for forecasting pollution concentrations, cover the most important atmospheric processes favoring pollution episodes. The selection of the variables was based both on extensive correlation analysis and on the existing knowledge from the scientific literature. The evaluation of the developed forecasting models showed that their degree of success is promising. The final model equations derived are simple and they can be used easily for operational forecasts from the air quality management authorities.

Increased sensitization in urban vs. rural environment--rural protection or an urban living effect?

In a population‐based longitudinal cohort study, we tested the hypothesis that children growing up in a high‐traffic polluted urban area (UA) in the Athens’ basin have higher prevalence of allergies and sensitization when compared with those growing up in a Greek provincial rural area (RA). We recruited 478 and 342 children aged 8–10 living in the UA and the RA, respectively. Respiratory health was assessed by a parent‐completed questionnaire in three phases: 1995–96 (phase 1), 1999–2000 (phase 2), 2003–04 (phase 3) and skin‐prick testing to common indoor and outdoor aeroallergens was performed at phases 1 and 2. Reported asthma and eczema did not differ between the two areas, whereas reported hay fever was persistently more prevalent in the UA than in the RA (16.5%, 17.0%, 18.2% vs. 7.0%, 8.3%, 9.6%, respectively). Sensitization was more prevalent in the UA at both phases (19.0% vs. 12.1% in phase 1, 20.0% vs. 14.1% in phase 2). Residential area contributed independently to sensitization to ≥1 aeroallergens (OR: 0.29; 95% CI: 0.13–0.66; p = 0.003) and to polysensitization (OR: 0.28; 95% CI: 0.10–0.82; p = 0.020) in phase 1. These associations were independent of farming practices. No significant contributions were found in phase 2. Our results suggest that long‐term exposure to urban environment is associated with a higher prevalence of hay fever but not of asthma or eczema. The negative association between rural living and the risk of atopy during childhood, which is independent of farming practices, implies that it is mainly driven by an urban living effect.

Association of weather conditions with childhood admissions for wheezy bronchitis or asthma in Athens.

Background: The association between asthma morbidity and meteorological conditions is well documented, but it is not clear to what extent more specific meteorological variables are implicated. Objectives: This study was aiming to investigate whether there is any association between specific meteorological conditions and the seasonal variation and the rate of asthma admissions among children in Athens. Methods: Data were obtained retrospectively from hospital registries of the three main Children’s Hospitals in Athens during a 23-year period (1978–2000). The meteorological database consisted of mean monthly values of eight meteorological variables. The whole period studied was divided into three time periods: 1978–1987, 1988–1993 and 1994–2000. Results: A clear seasonal trend with a permanent pattern was detected. There were more monthly asthma admissions in winter-spring and autumn for younger children, as well as a lower peak in winter and autumn and a major one in May for older children, without significant differences in between the three time periods. The results of a multiple regression analysis revealed that relative humidity and atmospheric pressure were predictors of up to 56.7% (1988–1993) and 59.2% (1994–2000) monthly asthma admissions among younger children. No relation of the time trend in asthma admissions during the periods studied for any age group with any of the meteorological variables was detected. Conclusions: Our results indicate a constant seasonal variability in asthma admissions among children in Athens, whereas relative humidity and atmospheric pressure are the more implicated meteorological variables for younger asthmatic children.

Case study of UV-B modification during episodes of urban air pollution

Examination of the record of solar ultraviolet measurements made during the MEDCAPHOT study of air pollution in the Athens basin revealed a substantial reduction of UV-B on days with high levels of pollution. The magnitude of this relation is illustrated by a comparison of the UV on two days of a pollution episode with that on two days of low pollution.

The Effect of Weather Variability on Pediatric Asthma Admissions in Athens, Greece

The aim of this study was to determine whether there is any association between weather variability and asthma admissions among children in Athens, Greece. Medical data were obtained from hospital registries of the three main Childrens Hospitals in Athens during the 1978–2000 period; children were classified into two age groups: 0–4 and 5–14 years. The application of Generalized Linear Models with Poisson distribution revealed a significant relationship among asthma hospitalizations and the investigated parameters, especially for the children aged 0–4 years. Our findings showed that Hospital admissions for childhood asthma in Athens, Greece, is negatively correlated with discomfort index, air temperature and absolute humidity whereas there is a positive correlation with cooling power, relative humidity and wind speed.

Application of Multiple Linear Regression Models and Artificial Neural Networks on the Surface Ozone Forecast in the Greater Athens Area, Greece

An attempt is made to forecast the daily maximum surface ozone concentration for the next 24 hours, within the greater Athens area (GAA). For this purpose, we applied Multiple Linear Regression (MLR) models against a forecasting model based on Artificial Neural Network (ANN) approach. The availability of basic meteorological parameters is of great importance in order to forecast the ozone’s concentration levels. Modelling was based on recorded meteorological and air pollution data from thirteen monitoring sites within the GAA (network of the Hellenic Ministry of the Environment, Energy and Climate Change) over five years from 2001 to 2005. The evaluation of the performance of the constructed models, using appropriate statistical indices, shows clearly that in every aspect, the prognostic model by far is the ANN model. This suggests that the ANN model can be used to issue warnings for the general population and mainly sensitive groups.

Diffuse solar irradiation at a location in the Balkan Peninsula

This study correlates experimental values with modelled values of global (KT) and diffuse (KD) clearness index in Athens, Greece. The experimental values come from measurements of daily global and diffuse solar irradiation on horizontal surface, while the modelled ones are from linear regression expressions fitted to the experimental data. It is found that the correlations give excellent results for nearly all experimental periods considered (1990–2000). The study also tries to correlate KT values with black smoke (BS) concentration. The analysis shows that there is no significant trend in KT, which would reflect an increase or decrease in light scattering by BS.

Energy consumption based on heating/cooling degree days within the urban environment of Athens, Greece

The degree-day method is considered to be a fundamental and a rather simple method to estimate heating and cooling energy demand. This study aims in a detailed and accurate assessment of cooling and heating degree days in different locations within the Greater Athens area (GAA), Greece. To achieve this goal, hourly values of air temperature from eight different locations within the GAA, covering the period 2001–2005, were used. Thus, the monthly and the annual number of cooling and heating degree days for each one of the examined locations could be estimated separately. Furthermore, an effort is made to evaluate the energy consumption for a specific building, based on the degree-day method, to indicate the impact of the canopy layer urban heat island on neighboring regions within the GAA. Results reveal that there is great spatial variability of energy demand and energy consumption along with significant differences in expenses for heating and cooling among neighboring regions within the GAA. Finally, regarding the energy demands of buildings, it is important to take into account intra-urban variability of canopy layer climates against an ensemble mean throughout the city, because the latter can result in inaccurate estimations and conclusions.

Diagnosis of the Relationship between Dust Storms over the Sahara Desert and Dust Deposit or Coloured Rain in the South Balkans

The main objects of study in this paper are the synoptic scale atmospheric circulation systems associated with the rather frequent phenomenon of coloured rain and the very rare phenomenon of dust or sand deposits from a Saharan sandstorm triggered by a developing strong depression. Analysis of two such cases revealed that two days before the occurrence of the coloured rain or the dust deposits over Greece a sand storm appeared over the north-western Sahara desert. The flow in the entire troposphere is southerly/south-westerly with an upward vertical motion regime. If the atmospheric conditions over Greece favour rain then this rain contains a part of the dust cloud while the rest is drawn away downstream adopting a light yellow colour. In cases where the atmospheric circulation on the route of the dust cloud trajectories is not intensively anticyclonic dust deposits can occur on the surface long far from the region of the dust origin. Such was the case on 4th April, 1988, when significant synoptic-scale subsidence occurred over Italy and towards Greece. The upper air data, in the form of synoptic maps, illustrate in detail the synoptic-scale atmospheric circulations associated with the emission-transport-deposition and confirm the transportation of dust particles.