Atmospheric Circulation Types and Daily Mortality in Athens, Greece.We investigated the short-term effects of synoptic syn·op·tic also syn·op·ti·cal adj. 1. Of or constituting a synopsis; presenting a summary of the principal parts or a general view of the whole. 2. a. Taking the same point of view. b. and mesoscale atmospheric circulation Atmospheric circulation is the large-scale movement of air, and the means (together with the smaller ocean circulation) by which heat is distributed on the surface of the Earth. types on mortality in Athens, Greece. The synoptic patterns in the lower troposphere troposphere: see atmosphere. troposphere Lowest region of the atmosphere, bounded by the Earth below and the stratosphere above, with the upper boundary being about 6–8 mi (10–13 km) above the Earth's surface. were classified in 8 a priori a priori In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. defined categories. The mesoscale weather types were classified into 11 categories, using meteorologic me·te·or·ol·o·gy n. The science that deals with the phenomena of the atmosphere, especially weather and weather conditions. [French météorologie, from Greek parameters from the Athens area surface monitoring network; the daily number of deaths was available for 1987-1991. We applied generalized additive models In statistics, the generalized additive model (or GAM) is a statistical model developed by Trevor Hastie and Rob Tibshirani blending properties of multiple regression (a special case of general linear model) with additive models. (GAM), extending Poisson regression In statistics, the Poisson regression model attributes to a response variable Y a Poisson distribution whose expected value depends on a predictor variable x, typically in the following way: when the effects of two, or more, processes on results cannot be separated, the results are said to be confounded, a cause of bias in disease studies. confounding factor effects of seasonal patterns. We adjusted for long-term trends, day of the week, ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. particle concentrations, and additional temperature effects. Both classifications, synoptic and mesoscale, explain the daily variation of mortality to a statistically significant degree. The highest daily mortality was observed on days characterized by southeasterly south·east·er·ly adj. 1. Situated toward the southeast. 2. Coming or being from the southeast. south·east flow [increase 10%; 95% confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. (CI), 6.1-13.9% compared to the high-low pressure system), followed by zonal flow Zonal flow is a meteorological term meaning that the general flow pattern is west to east along the earth's latitude lines (as opposed to meridional flow). Extratropical cyclones in this environment tend to be weaker, moving faster and producing relatively little impact on local (5.8%; 95% CI, 1.8-10%). The high-low pressure system and the northwesterly north·west·er·ly adj. 1. Situated toward the northwest. 2. Coming or being from the northwest. north·west flow are associated with the lowest mortality. The seasonal patterns are consistent with the annual pattern. For mesoscale categories, in the cold period the highest mortality is observed during days characterized by the easterly flow category (increase 9.4%; 95% CI, 1.0-18.5% compared to flow without the main component). In the warm period, the highest mortality occurs during the strong southerly flow category (8.5% increase; 95% CI, 2.0-15.4% compared again to flow without the main component). Adjusting for ambient particle levels leaves the estimated associations unchanged for the synoptic categories and slightly increases the effects of mesoscale categories. In conclusion, synoptic and mesoscale weather classification is a useful tool for studying the weather-health associations in a warm Mediterranean climate A Mediterranean climate is a climate that resembles the climate of the lands in the Mediterranean Basin. Outside the Mediterranean, this climate covers relatively small areas of the Earth, and generally occurs on the western coasts of continental landmasses, roughly between situation. Key words. Athens, human mortality, mesoscale classification, synoptic classification. Environ en·vi·ron tr.v. en·vi·roned, en·vi·ron·ing, en·vi·rons To encircle; surround. See Synonyms at surround. [Middle English envirounen, from Old French environner Health Perspect 109:591-596 (2001). [Online 7 June 2001] http://ehpnet1.niehs.nih.gov/docs/2001/ 109;591-596kassomenos/abstract.html It has been known for a long time that there is an association between weather and mortality (1). The pattern of seasonality associated with mortality reflects medium- and short-term effects of weather, both direct and indirect. Thus, respiratory disease Noun 1. respiratory disease - a disease affecting the respiratory system respiratory disorder, respiratory illness adult respiratory distress syndrome, ARDS, wet lung, white lung - acute lung injury characterized by coughing and rales; inflammation of the epidemics and other cold weather related events lead to increased winter mortality (2), and the same appears to be true for behavioral factors related to clothing and heating (3). In contrast, extremely high temperatures are related to sharp, short-term increases in mortality (4-6). The short-term association of weather parameters with mortality over the whole range of variation (i.e., on an annual basis) has been addressed by only a few studies and those have mainly focused on temperature. The dose-response curve dose-response curve A graphic representation of the effects that varous doses of an agent–eg, ionizing radiation or a chemotherapeutic agent, have on a given parameter–eg, cell viability, mutation frequency, DNA damage, tumor growth or metastasis or has been examined and, in some instances, a changing point was identified above and below the point where mortality rates rose. The form of the temperature--mortality relationship has often been referred to as "J-shaped" because of the asymmetrical a·sym·met·ri·cal or a·sym·met·ric adj. Abbr. a Lacking symmetry between two or more like parts; not symmetrical. pattern of association with a rise in mortality counts that is steeper and shorter for high than for low temperatures. The temperature with the lowest observed mortality varied by geographic region. Thus, the minimum mortality rates occurred when the average daily temperature was around 16.5 [degrees] C in the Netherlands (7) and 22 [degrees] C in Athens, Greece (8). Temperature and humidity (relative or dew point dew point: see dew. ) have often been used to control the confounding effects of weather in studies of air pollution and mortality (9). Bioclimatologists believe that only one or two weather variables, such as temperature and humidity, cannot fully account for the impact of climate and weather on biological organisms and systems or for controlling their confounding effects. Treating temperature and humidity as separate variables in multiple regression Multiple regression The estimated relationship between a dependent variable and more than one explanatory variable. analyses with a health outcome as the dependent variable ignores the natural association between weather elements, the combined effect of which may have the most important influence on human health. A series of composite indices have therefore been developed such as human discomfort indices (10), heat budgets (11), and synoptic climatologic classifications (12). Synoptic weather systems are considered to play an important role on human health over a specific area through their controlling effect on local meteorologic conditions. Some investigators have tried to correlate the prevailing large-scale (synoptic) weather systems (systems extending over an area of at least 1,000,000 [km.sup.2]) with human health. More precisely, Kalkstein (12) proposed a synoptic weather system classification based on air mass type, and used this to evaluate the impact of meteorologic conditions on human mortality. Pope and Kalkstein (13) and Samet et al. (14) estimated the association between particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. air pollution and daily mortality in Utah Valley Utah Valley is a valley in North Central Utah located in Utah County, and is considered part of the Wasatch Front. It contains Provo, Orem, and their suburbs, including Spanish Fork and American Fork. Utah Lake is a natural shallow fresh water lake in its center. , Utah, and Philadelphia, Pennsylvania, using the synoptic meteorologic approach to control for potential confounding weather effects, but the objective of these studies focused on air pollution and not on weather effects. None of the above researchers have tried to correlate medium range weather systems (mesoscale; i.e. systems that cover an area of at most 10,000 [km.sup.2]) with health. The objective of this study was to investigate the short-term relationship between both large and mesoscale weather systems occurring in the lower troposphere and daily mortality in Athens. We examined the daily meteorologic conditions over Athens using both the synoptic and mesoscale atmospheric circulation classification schemes proposed by Kassomenos et al. (15,16) and studied their relationship with mortality data for the years 1987-1991 in Athens. Methods Study area. Athens is situated in a small peninsula located in the southeastern edge of the Greek mainland. It covers about 450 [km.sup.2] and has 3,600,000 inhabitants
The game is based loosely on the concepts from SameGame. . The built-up area built-up area n → bebautes Gebiet nt built-up area n → abitato is mainly located in a basin surrounded by high and rather stony ston·y also ston·ey adj. ston·i·er, ston·i·est 1. Covered with or full of stones: a stony beach. 2. Resembling stone, as in hardness. 3. a. mountains on three sides and open to the sea from the south (17). There are small openings connecting the metropolitan area of Athens with the Greek mainland on the north, northwest, and northeast sides of the basin. In Athens, more than 1,500,000 cars are registered; industrial activities are mainly located in the west and southwest of the basin. Meteorologic data. We obtained the synoptic charts for 00 and 12 Greenwich mean time Greenwich mean time or Greenwich meridian time (GMT), the former name for mean solar time at the original site of the Royal Observatory in Greenwich, England, which is located on the prime meridian. covering the period 1983-1995 on a daily basis from the archives of the European Meteorological me·te·or·ol·o·gy n. The science that deals with the phenomena of the atmosphere, especially weather and weather conditions. [French météorologie, from Greek Bulletin. In the Metropolitan area of Athens, a monitoring network of seven surface meteorologic stations has been operating. Five of these stations are located inside the Athens basin, whereas the other two are on the eastern and western sides of it, in the nearby Mesogia and Thriassion plains, respectively. The primary meteorologic parameters that are recorded are wind speed and direction, air temperature, relative humidity relative humidity n. The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. , and cloudiness (16). Synoptic classification. The classification of the large-scale atmospheric circulation patterns in the lower troposphere was carried out at the isobaric isobaric /iso·bar·ic/ (i?so-bar´ik) having equal or constant pressure or weight across space or time. i·so·bar·ic adj. 1. Having equal weights or pressures. 2. levels of 850 and 700 hectopascal (hPa; about 1,500-3,000 m above mean sea level); the isobaric level of 700 hPa was used as auxiliary. These isobaric levels characterize the large-scale atmospheric circulation over the examined area, independently of topographic topographic describing or pertaining to special regions. effects (the mountain tops around Athens are lower than 1,500 m). Regarding the synoptic circulation patterns over Athens, we defined a priori eight categories according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the general circulation patterns, the position of the synoptic systems with respect to Athens, and the orientation of the trough Trough The stage of the economy's business cycle that marks the end of a period of declining business activity and the transition to expansion. or ridge axis. These a priori-determined categories were shown to be statistically distinct with respect to their thermodynamic ther·mo·dy·nam·ic adj. 1. Characteristic of or resulting from the conversion of heat into other forms of energy. 2. Of or relating to thermodynamics. characteristics. Details of the classification have been previously published (16), but a brief description is presented in Table 1. The frequency of occurrence of most of the above synoptic categories displays seasonality.
Table 1. Description of synoptic weather types in the Athens area.
Synoptic weather type Weather conditions
Open cyclone (OC) Northwestern cold, dry winds
Southwesterly flow (SW) Humid and warm air from the sea
Northwesterly flow (NW) Cooler winds during summer, cold during
winter; low relative humidity
Zonal flow (ZN) Weak westerly/southwesterly winds
Closed cyclone (CC) Strong, dry winds from the north
Open anticyclone (OA) Persistent weak flows, moderate-to-low
relative humidity, and enhanced
temperature
Closed anticyclone (CA) Humid weak winds and temperature extremes
Combination between a Moderate to strong northern or northeastern
high pressure system dry winds
and a low pressure
system (HL)
Classification of mesoscale weather types. The methodology applied for the classification of mesoscale categories, using meteorologic parameters from the surface monitoring network operated in the area, has been extensively discussed and analyzed an·a·lyze tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es 1. To examine methodically by separating into parts and studying their interrelations. 2. Chemistry To make a chemical analysis of. 3. (15). The mesoscale surface airflow in the Athens basin can be divided in 11 categories that are briefly described in Table 2. Not all mesoscale types appear during both winter and summer. Some are exclusive to the warm period, while others are exclusive to the cold. The cold period is from approximately November to April inclusive, and the rest of the year is considered warm. Details on the definitions of the warm and cold periods of the year were presented by Maheras (18) and Lykoudis et al. (19).
Table 2. Description of mesoscale weather types in Athens.
Mesoscale weather type Weather conditions
Westerly flow (a) Winds of medium intensity, reduced
humidity, and moderate temperature
Easterly flow (b) Very low temperatures, rather weak
winds, and snow
Strong northerly flow during Strong and cold dry winds from the
the cold period (c1) north
Weak northerly flow during Moderate and cold dry winds from the
the cold period (c2) north.
Strong northerly flow during Strong and cool, almost dry, winds from
the warm period (c3) the north
Weak northerly flow during Moderate and cool, almost dry, winds
the warm period (c4) from the north
Strong southerly flow (d1) Increased temperature and moist air
masses
Pure sea breeze (d2) Increased relative humidity and winds
of moderate strength from the south
Weak sea breeze (d3) Increased relative humidity and weak
winds from the south
Very weak southerly flow Humid, very weak winds from the sea
(d4)
Flow without main component Moderate temperature and humidity;
(f) very weak winds blowing from various
directions.
Mortality data. The number of daily deaths for the period 1 January 1987-30 December 1991 (a total of 1,826 days) was recorded from the Athens Town Registry and the registries of all 19 towns contiguous to Athens. In July 1987 in Athens, there was a 9-day heat wave characterized by maximum daily temperatures [is greater than] 35 [degrees] C ([is greater than] 40 [degrees] C on 6 days) and open anticyclone anticyclone, region of high atmospheric pressure; anticyclones are commonly referred to as "highs." The pressure gradient, or change between the core of the anticyclone and its surroundings, combined with the Coriolis effect, causes air to circulate about the core in winds (OA; northwestern cold, dry winds). The total number of daily deaths during this month increased by more than 100%, and this period was excluded from all further analyses as a climatic outlier outlier /out·li·er/ (out´li-er) an observation so distant from the central mass of the data that it noticeably influences results. outlier an extremely high or low value lying beyond the range of the bulk of the data. . After this exclusion, the mean ([+ or -] SD) daily deaths during the study period was 37.2 [+ or -] 8.0. Air quality data. Particulate air pollution is associated with health effects (8,9,13,14). To measure ambient particles in Athens, we used the method of black smoke (BS), a photometric pho·tom·e·try n. Measurement of the properties of light, especially luminous intensity. pho  to·met index assessed on the
basis of black particles with an aerodynamic diameter Drug particles for pulmonary delivery are typically characterized by aerodynamic diameter rather than geometric diameter. The velocity at which the drug settles is proportional to the aerodynamic diameter, da. [is less than] 4.5
[micro]m.The air pollution measurements were provided by the Monitoring Network operated by the Ministry of Environment, Planning and Public Works public works pl.n. Construction projects, such as highways or dams, financed by public funds and constructed by a government for the benefit or use of the general public. Noun 1. . BS was measured by the method of the Organisation for Economic Co-operation and Development The Organisation for Economic Co-operation and Development (OECD), (in French: Organisation de coopération et de développement économiques; OCDE) is an international organisation of thirty countries that accept the principles of representative democracy and a free market (20). For completeness of the pollution time-series data, we used the average daily measurements of three stations (Patision, Aristotelous, and Piraeus) for BS (24-hr level in micrograms per cubic meter Noun 1. cubic meter - a metric unit of volume or capacity equal to 1000 liters cubic metre, kiloliter, kilolitre metric capacity unit - a capacity unit defined in metric terms ). These stations cover the study area and are representative of the population exposure (8). During this period, BS exceeded the World Health Organization air quality guideline guideline Medtalk A series of recommendations by a body of experts in a particular discipline. See Cancer screening guidelines, Cardiac profile guidelines, Gatekeeper guidelines, Harvard guidelines, Transfusion guidelines. (21) on 42% of the days in the center of Athens (Patision), where the highest levels were observed for all pollutants pollutants see environmental pollution. . Missing values In statistics, missing values are a common occurrence. Several statistical methods have been developed to deal with this problem. Missing values mean that no data value is stored for the variable in the current observation. in each station were completed as described by Katsouyanni et al. (22). Statistical methods. We applied generalized additive models (GAM), extending Poisson regression to model the nonlinear A system in which the output is not a uniform relationship to the input. nonlinear - (Scientific computation) A property of a system whose output is not proportional to its input. effects of the covariates; we used a LOESS smoother to control for seasonal patterns and long-term trends and allowed for over dispersion dispersion, in chemistry dispersion, in chemistry, mixture in which fine particles of one substance are scattered throughout another substance. A dispersion is classed as a suspension, colloid, or solution. (23). To determine the smoothing parameter (i.e., the fraction of the data used for smoothing), we used diagnostic tools including partial autocorrelation Autocorrelation The correlation of a variable with itself over successive time intervals. Sometimes called serial correlation. plots and plots of residuals over time. We had decided in advance that the smoothing window should not be [is less than] 2 months in order to avoid eliminating short-term patterns, which may actually be due to the exposure under study. After controlling for seasonal and long-term trends, we incorporated temperature into the model. We investigated smoothed functions of the same day and of lags up to 2 days or those averaged over 1-3 days of daily mean temperature. Temperature on the same day was always included. The inclusion of lagged temperature variables and the choice of smoothing parameters were based on minimizing Akaike's information criterion There are a number of statistics that can act as an information criterion. They include:
In regression analysis, a dummy variable to the model to control for day of the week. Finally, we included dummy variables for the synoptic and mesoscale categories alternatively. Because of the seasonal patterns displayed, the analysis was conducted for the synoptic categories, both for the whole period and separately by season. For the mesoscale categories we conducted analysis only by season. Finally, BS concentration was included as a linear term (average of lags 0 and 1) in the model to adjust for the potential confounding effects of air pollution. Results In Figures 1 and 2 we present the frequency of occurrence of synoptic and mesoscale categories by season over the study period. Several synoptic categories display a seasonal pattern: dosed cyclone cyclone, atmospheric pressure distribution in which there is a low central pressure relative to the surrounding pressure. The resulting pressure gradient, combined with the Coriolis effect, causes air to circulate about the core of lowest pressure in a (CC), southwesterly south·west·er·ly adj. 1. Situated toward the southwest. 2. Coming or being from the southwest. south·west flow (SW), and zonal flow (ZN) occur more often during winter; high-low pressure system (HL) occurs more often during summer; whereas northwesterly flow (NW), open anticyclone (OA), and open cyclone (OC) display limited seasonality and dosed anticyclone (CA) is equally distributed between seasons. The mesoscale categories have a stronger seasonal pattern: categories b (easterly flow), c1-c2 (strong or weak northerly flow during cold period), and d4 (very weak southerly flow) are only defined during winter; c3-c4 (strong or weak northerly flow during warm period), d2 (pure sea breeze sea breeze n. A cool breeze blowing from the sea toward the land. sea breeze Noun a breeze blowing inland from the sea Noun 1. ) and d3 (weak sea breeze) are only defined during summer; and only f (flow without main component) and d1 (strong southerly flow) appear in both seasons. [GRAPHS OMITTED] Table 3 shows the frequency of occurrence, the mean daily number of deaths, and the average BS concentrations for each synoptic weather category by season. There are seasonal differences in mortality and BS levels as well as differences among the different synoptic categories. The category most often observed in both seasons is OA, an extended anticyclone covering the eastern Mediterranean, which is typical for the area of interest; other often observed categories are SW, CC, and OC in the winter and HL in the summer.
Table 3. Daily total number of deaths and airborne particulate
matter concentrations (as indicated by BS measurements) by
synoptic weather categories and season.
Winter
No. of Daily no. BS ([micro]g/
Synoptic type days (%) of deaths [m.sup.3])
CA 23 (2) 38.1 106.0
CC 108 (12) 39.4 66.6
HL 82 (9) 35.9 76.6
NW 79 (9) 39.3 103.4
OA 339 (37) 39.4 108.3
OC 93 (10) 40.0 89.2
SW 114 (13) 40.1 93.5
ZN 73 (8) 41.4 121.8
Total 911 (100) 39.8 94.5
Summer
No. of Daily no. BS ([micro]g/
Synoptic type days (%) of deaths [m.sup.3])
CA 22 (2) 35.5 96.9
CC 41 (5) 35.9 54.9
HL 174 (20) 33.7 59.6
NW 63 (7) 33.8 66.9
OA 408 (46) 34.6 79.3
OC 79 (9) 34.8 61.0
SW 48 (5) 36.4 64.5
ZN 49 (6) 33.4 73.6
Total 884 (100) 34.1 74.1
Table 4 shows the frequency of occurrence, the mean daily number of deaths, and the average BS concentrations for the mesoscale categories. The categories most often observed are c1 and c2 in the cold season and c3 and c4 in the warm season. These categories are associated with a prevailing northern flow (strong or moderate), which is the wind flow most often observed in Athens. In winter, this is followed by the occurrence of f, whereas in the summer it is followed by d2 and d3.
Table 4. Daily number of deaths and airborne particulate matter
concentrations (as indicated by BS measurements) by mesoscale
categories and season.
Winter
No. of Daily no BS ([micro]g/
Mesoscale type days (%) of deaths [m.sup.3])
a 34 (4) 38.3 76.5
b 19 (3) 41.1 74.0
c1,c2 303 (39) 40.6 76.6
c3,c4
d1 61 (8) 40.2 87.7
d2
d3
d4 114 (15) 39.4 118.6
f 239 (31) 39.3 117.4
Total 770 (100) 39.9 96.3
Summer
No. of Daily no BS ([micro]g/
Mesoscale type days (%) of deaths [m.sup.3])
a 40 (5) 32.1 65.9
b 3 (0.5) 34.7 75.9
c1,c2
c3,c4 346 (41) 33.8 62.8
d1 45 (5) 36.6 72.2
d2 147 (18) 35.4 91.4
d3 151 (18) 34.1 81.6
d4
f 101 (12) 33.4 79.0
Total 837 (100) 34.2 73.9
Table 5 shows the cross-classification of synoptic and mesoscale categories. Although there is considerable association, there is also a degree of independence in the two classifications. This is probably due to the fact that a synoptic system is larger than a mesoscale and the projection of this system to smaller scales could lead to more than one mesoscale system.
Table 5. Cross-classification of synoptic and mesoscale categories.
Synoptic category
Mesoscale
category CA CC HL NW OA OC SW ZN
a 1 7 4 8 20 11 10 13
b 0 4 2 3 6 1 3 3
c1,c2 5 68 37 32 103 36 11 12
c3,c4 5 25 140 18 135 17 1 5
d1 1 3 2 3 44 3 42 8
d2 6 3 9 12 67 15 11 24
d3 6 3 17 14 85 16 3 7
d4 0 5 4 13 54 10 18 13
f 13 17 19 23 165 41 39 23
Tables 6 and 7 show the relative risks for daily mortality for each synoptic weather category for the time period and separately by season. The smallest number of daily deaths after adjusting for season, long-term trends, temperature, and day of the week was observed during days with weather characterized by HL (reference category) and NW synoptic weather categories. The highest number of daily deaths was observed during days with SW [increase in the daily number of deaths 10%; 95% confidence interval (CI), 6.1-13.9%, compared to the reference], followed by ZN (increase 5.8%; 95% CI, 1.8-10%), OC (increase 5.3%; 95% CI, 1.7-9%), and finally CC, CA, and OA categories. In seasonal analysis during the cold period, a similar pattern was observed, with days characterized by the SW category displaying the highest mortality, followed by ZN, CC, and OA and days with HL displaying the lowest. During the warm period, days with HL and NW had the lowest mortality and days with SW the highest, but days with ZN did not display increased mortality, whereas days with OC do (increase 6.6%; 95% CI, 1.3-12.2%).
Table 6. Relative risks (RRs) and associated 95% CIs for mortality
from generalized additive Poisson models, for each synoptic weather
category, for the whole year, before and after adjusting for ambient
BS concentrations.
Base model(a) Adjusted also for BS
Synoptic category RR (95% CI) RR (95% CI)
HL Reference Reference
SW 1.100 (1.061-1.139) 1.098 (1.060-1.138)
CC 1.035 (0.997-1.075) 1.038 (1.000-1.078)
CA 1.044 (0.987-1.104) 1.028 (0.971-1.087)
ZN 1.058 (1.018-1.100) 1.044 (1.004-1.085)
OC 1.053 (1.017-1.090) 1.046 (1.010-1.083)
OA 1.034 (1.008-1.062) 1.022 (0.996-1.049)
NW 0.998 (0.961-1.036) 0.994 (0.958-1.033)
(a) Adjusting for season, long-term trends, temperature,
and day of the week.
Table 7. Relative risks (RRs) and associated 95% CIs for mortality
from generalized additive Poisson models, for each synoptic weather
category, separately by season, before and after adjusting for
ambient BS concentrations.
Cold period
Synoptic Base model(a) Adjusted also for BS
category RR (95% CI) RR (95% CI)
HL Reference Reference
SW 1.102 (1.044-1.164) 1.104 (1.046-1.165)
CC 1.059 (1.004-1.118) 1.067 (1.011-1.126)
CA 1.083 (0.993-1.182) 1.072 (0.982-1.169)
ZN 1.089 (1.028-1.154) 1.081 (1.020-1.145)
OC 1.053 (0.997-1.112) 1.050 (0.994-1.109)
OA 1.056 (1.007-1.107) 1.048 (1.000-1.099)
NW 1.016 (0.960-1.075) 1.015 (0.959-1.074)
Warm period
Synoptic Base model(a) Adjusted also for BS
category RR (95% CI) RR (95% CI)
HL Reference Reference
SW 1.104 (1.034-1.178) 1.096 (1.027-1.169)
CC 1.025 (0.962-1.091) 1.021 (0.959-1.087)
CA 1.016 (0.942-1.095) 1.003 (0.930-1.081)
ZN 1.011 (0.952-1.074) 1.002 (0.944-1.064)
OC 1.066 (1.013-1.122) 1.057 (1.005-1.112)
OA 1.017 (0.985-1.050) 1.007 (0.975-1.039)
NW 0.998 (0.943-1.056) 0.993 (0.939-1.050)
(a) Adjusting for season, long-term trends, temperature,
and day of the week.
After adjusting for ambient particulate levels, the relative risks for some synoptic categories remained practically identical (SW, CC, and NW). For other categories there was some indication of confounding and the relative risks decreased slightly, but the same pattern was preserved (CA, ZN, OC, OA). In seasonal analysis, there is no confounding by pollution levels. Table 8 presents the relative risks for daily mortality for the mesoscale categories for each season. The differences in mortality for mesoscale categories are not as evident as for synoptic categories. In the cold period the highest daily number of deaths was observed for days in category b (increase 9.4%; 95% CI, 1.0-18.5%), especially after adjusting for BS (increase 11.1%; 95% CI, 2.6-20.3%); this is followed by days in category d1 (the increase becomes greater and statistically significant after adjusting for BS: 5.3%; 95% CI, 0.3-10.6%). During the warm period, days in category d1 also display higher relative risks (increase 8.5%; 95% CI, 2.0-15.4%). Adjustment for BS levels tends to increase the relative risks for mesoscale categories, especially during the winter period.
Table 8. Relative risks (RRs) and associated 95% CIs for mortality
from generalized additive Poisson models for each mesoscale
category by season, before and after adjusting for ambient BS
concentrations.
Cold period
Mesoscale Base model(a) Adjusted also for BS
category RR (95% CI) RR (95% CI)
f Reference Reference
a 1.007 (0.946-1.071) 1.025 (0.963-1.092)
b 1.094 (1.010-1.185) 1.111 (1.026-1.203)
c1,c2 1.004 (0.971-1.039) 1.017 (0.983-1.052)
c3,c4 -- --
d1 1.039 (0.990-1.091) 1.053 (1.003-1.106)
d2 -- --
d3 -- --
d4 1.020 (0.981-1.060) 1.020 (0.982-1.060)
Warm period
Mesoscale Base model(a) Adjusted also for BS
category RR (95% CI) RR (95% CI)
f Reference Reference
a 0.994 (0.929-1.063) 1.006 (0.940-1.076)
b -- --
c1,c2 -- --
c3,c4 0.993 (0.954-1.035) 1.009 (0.968-1.051)
d1 1.085 (1.020-1.154) 1.094 (1.028-1.164)
d2 1.036 (0.988-1.086) 1.039 (0.992-1.089)
d3 1.019 (0.973-1.066) 1.023 (0.977-1.070)
d4 -- --
(a) Adjusted for season, long-term trends, temperature,
and day of the week.
Table 9 shows the relative risks associated with a 10-[micro]g/[m.sup.3] increase in daily BS concentrations in the different models, including synoptic and mesoscale categories. The risks for BS remain statistically significant in all models and are slightly higher during the summer compared to the winter season.
Table 9. Relative risks (RRs) and associated 95%
CIs from generalized additive Poisson models for
BS, adjusted for synoptic or mesoscale weather
categories.
RR (95% CI)
Adjusted for per 10 [micro]g/[m.sup.3]
Synoptic categories
All year 1.008 (1.006-1.010)
Cold period 1.005 (1.002-1.012)
Warm period 1.008 (1.003-1.012)
Mesoscale categories
Cold period 1.006 (1.003-1.009)
Warm period 1.008 (1.003-1.012)
Discussion In this study we observed associations of daily synoptic and mesoscale weather conditions with the daily number of deaths in Athens, Greece, an area with typical Mediterranean climate. We also adjusted for confounding by air pollution using ambient particles concentrations. We found that both atmospheric circulation classifications and air pollution have independent effects on mortality. In this analysis we adjusted for seasonal patterns using LOESS smoothers to ensure adequate control of seasonality in annual and seasonal models. Synoptic circulation systems. We used the HL synoptic type as the baseline or reference category to which all the risks for mortality for the other synoptic categories were compared. This category induces strong northeasterly north·east·er·ly adj. 1. Situated toward the northeast. 2. Coming or being from the northeast. north·east flow known as Etesians over the Aegean Sea Aegean Sea, Gr. Aigaion Pelagos, Turkish Ege Denizi, arm of the Mediterranean Sea, c.400 mi (640 km) long and 200 mi (320 km) wide, off SE Europe between Greece and Turkey; Crete and Rhodes mark its southern limit. and consequently over Athens, (18), mainly during the warm period of the year. This type of flow contributes significantly to the ventilation of the atmosphere over Athens and is associated with decreased mortality. We found that the most unfavorable synoptic circulation type was the SW type. This weather system is combined with southerly (especially southwesterly) flow. This flow is associated with a rapid increase of both temperature and relative humidity in the lower troposphere over the Aegean Sea due to the difference between the warm and moist air masses coming from North Africa, through the Mediterranean, and then through the relatively dry and cool air masses over the Greek mainland. The resulting high temperature (for the season) and humidity lead to intense thermal discomfort conditions. Especially during winter, the warm and moist weather of the SW type is very different from the normally expected weather conditions. The second most unfavorable synoptic type is the zonal flow (the normal westerly Westerly, town (1990 pop. 21,605), Washington co., extreme SW R.I., between the Pawcatuck River and Block Island Sound; inc. 1669. Its textile industry dates from 1814, and granite has been quarried there since c.1850. flow). This type of circulation results in usually weak westerlies The Westerlies or the Prevailing Westerlies are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. over the Athens area and is mostly combined with surface anticyclonic circulation and warm air in the south. However, when the zonal flow is intense, it seems to contribute to the establishment of pleasant weather conditions. This is usually the case during the warm period. The cyclonic cy·clone n. 1. Meteorology a. An atmospheric system characterized by the rapid inward circulation of air masses about a low-pressure center, usually accompanied by stormy, often destructive weather. synoptic types CC and OC, characterized by strong winds and bad weather conditions, are also shown to result in unfavorable conditions for human health. The anticyclonic types, OA and CA, result on persistent weak flows and temperature extremes and are also associated with increases in mortality. The estimated relative risks for CA and CC are not statistically significant although they are comparable to those of OA and CA, but this could be due to the very limited number of occurrences of these types. Overall, these categories are more favorable fa·vor·a·ble adj. 1. Advantageous; helpful: favorable winds. 2. Encouraging; propitious: a favorable diagnosis. 3. compared to the SW type; this is due to the lower humidity levels during the warm period. During the cold period, the anticylconic systems result in cold--sometimes very cold--and rather dry weather, which is more or less in line with the overall winter weather pattern. The only type of circulation that is comparable to HL, as far as the associated mortality level is concerned, is the NW type. This type is characterized by strong cold advection ad·vec·tion n. 1. The transfer of a property of the atmosphere, such as heat, cold, or humidity, by the horizontal movement of an air mass: from the north and northwest while the relative humidity remains quite low. Thus, the NW flow favors the development of good weather conditions. The seasonal variations of the relative risks associated to each synoptic category are a result of differences in frequency, persistence, and intensity of occurrence. The SW type presents the same relative risk during the two seasons. The zonal flow presents higher relative risks during the cold period than during the warm period. This circulation type is more frequent but less intense during the cold period compared to the warm period. A combination of weak wind flow, increased humidity, and increased temperature is responsible for unpleasant weather conditions during the cold period. The medium flow intensity during the warm period allows for local flows of reduced humidity and moderate temperature levels, leading to pleasant weather conditions over Athens, which may be the cause of the marked change of the associated relative risk. The anticyclonic types, CA and OA, conserve the meteorologic conditions. During the cold period, they are mostly associated with low intensity winds and temperature extremes. Temperature can be high or low depending on the previous synoptic conditions. Especially unfavorable conditions are developed when the Siberian anticyclone extends southerly over the Balkans, and extremely low temperatures are established for significant time periods. During the warm period, the very high temperatures are usually combined with moderate humidity levels, resulting in moderately unpleasant conditions. In the cold period, the NW type is frequently associated with very strong advection of polar air masses over Greece and the occurrence of cold outbreaks that produce health problems. During the warm period, the NW type is combined with pleasant weather conditions characterized by a medium intensity NW flow that ventilates the basin. The synoptic classification used here differs from that employed by Kalkstein (12). Kalkstein (12) used an air-mass objective classification scheme based on surface meteorologic data. The number of distinct categories and the actual classification were derived using principal component analysis and clustering techniques, and weather maps were used only to further illustrate differences between the identified categories. The classification scheme used by Kalkstein (12) in St. Louis, Missouri, resulted in 10 synoptic categories. The classification that we used in this paper is based on the position and orientation of synoptic scale geopotential height Geopotential height is a vertical coordinate referenced to Earth's mean sea level — an adjustment to geometric height (elevation above mean sea level) using the variation of gravity with latitude and elevation. Thus it can be considered a "gravity-adjusted height. patterns with respect to the area of interest (Athens) (15). Although it is a subjective scheme, two researchers performed the classification independently using the 850 and 700 hPa synoptic weather maps to assign each day into 1 of the 8 predefined categories; there was good agreement (80%) between results of both researchers. The categories were later shown to be statistically distinct by discriminant dis·crim·i·nant n. An expression used to distinguish or separate other expressions in a quantity or equation. analysis (15). The classification used by Kalkstein (12) is directly related to the surface thermohygrometric (TH) conditions of a large area around the point of interest, whereas our classification is based on the atmospheric circulation patterns resulting from the vertical TH structure of the atmosphere, which in turn is inter-linked with the surface conditions. A unique relationship between synoptic category and surface weather conditions, as is the case with Kalkstein's classification (12), is possible only under strong synoptic flows (e.g., SW, NW, CC). Under weak synoptic conditions, local circulations become the dominant factors that shape surface weather conditions. Observed synoptic weather systems are not the same all over the world, so it is expected that the weather systems identified for the central United States The Central United States is sometimes conceived as between the Eastern United States and Western United States as part of a three-region model, roughly coincident with the Midwestern United States plus the western and central portions of the Southern United States; the term is will be quite different from those identified for Greece. This is especially true because both the land-sea distribution and the physiographical characteristics of the two areas are very different, despite the fact that they lay in similar latitudes. In contrast, similar surface weather conditions are expected to produce similar effects on human health. Athens is a city built on the Mediterranean coastline close to the Sahara desert; as a result, air masses coming from the south are very warm and wet because they have to cross the Mediterranean before reaching Athens. It is therefore expected that the southwestern flow is the most unfavorable category for human health because it is also combined with an abrupt temperature change. For St. Louis, the worst categories are also characterized by winds from the southern sector. These wind flows have their origin in the Caribbean, but in order to reach St Louis, they have to cross an extended land mass, losing significant amounts of water yet remaining wet. These categories appear with similar frequencies (7-10%) in both cities. The synoptic category characterized with the lowest risk of death both in Athens and in St. Louis is Louis I, king of Bavaria Louis I, 1786–1868, king of Bavaria (1825–48), son and successor of King Maximilian I. He was chiefly responsible for transforming Munich into one of the handsomest capitals of Europe and for making it a center of the associated with NW wind combined with cold northern flows. The frequency of occurrence of this synoptic category is about 6% for St. Louis and a little higher (8-9%) for Athens. The anticyclonic categories, which represent a moderate risk for mortality, occur in Athens on more than 40% of the days, but in St. Louis they occur on about 30% of days. Mesoscale circulation systems. As outlined above, the synoptic systems are closely associated to surface weather only when they represent intense flows. The mesoscale atmospheric circulation patterns correspond to smaller areas and thus are directly related to surface weather. We used these circulation patterns to better illustrate the effect of local flows (dominant under weak synoptic conditions) on health. To study the association between mesoscale circulation patterns and mortality, we used the flow without main component (f) as a baseline because it occurs frequently in both seasons. This mesoscale pattern is characterized by low intensity winds blowing from various directions, and moderate temperature and humidity. Due to the slight movement of the air, the meteorologic conditions associated with it are pleasant. Among the mesoscale circulation patterns, the one associated with the highest relative risk for mortality in the summer in Athens is d1. This pattern is associated with strong southerly winds responsible for the transportation of warm and moist air masses from the Aegean Sea over Athens. The increased temperature combined with the moist air masses create uncomfortable conditions in Athens. The mesoscale weather type associated with the highest relative risks in the winter is type b, representing easterly winds. The easterly winds are a very rare pattern appearing during the cold period of the year and are associated with cold outbreaks, very low temperatures, rather weak wind, and snow. Type d4 is also associated with elevated relative risks in the winter, and d2 is associated with elevated relative risks in the summer, d4 is a cold period circulation pattern combined with southern winds of low intensity, which carry moist air masses from the sea. During the winter there is increased humidity in the air compared to the summer, so relative humidity reaches high values. The increased relative humidity in association with very low intensity of winds and the increased temperature (for the season) creates unpleasant weather conditions, d2 is a circulation pattern, characterized by southern winds, that appears during the warm period and is associated with moderately unpleasant conditions. The mesoscale patterns a and c are not associated with elevated relative risks. The c1 and c2 types occur only during cold months. They are associated with good ventilation of the atmosphere in Athens and they result in the formation of pleasant weather conditions. The only difference between them is the intensity of the northern flow. Circulation pattern a is associated with western winds of medium intensity and reduced humidity; the temperature remains moderate and results in rather pleasant weather conditions. Although the mesoscale circulation types refer to a layer closer to the ground, they do not appear to improve our understanding of the association between weather types and mortality. This is probably because the local circulation is frequently associated with more than one synoptic condition. Although some intense synoptic categories successfully transfer their characteristics to some of the associated mesoscale categories (e.g., SW to d1), this is not generally the case. Further investigation is needed to obtain a better understanding. Ambient particle levels. The relative risks for mortality associated with exposures are comparable (or slightly higher) to the ones reported before in studies where control of confounding for weather variables was done using the mean daily levels of temperature and relative humidity (9,13). Thus, on the basis of an analysis of 12 European cities, Katsouyanni et al. (9) reported an increase of 0.6% in the daily number of deaths associated with a change of 10 [micro]g/[m.sup.3] in BS levels. In seasonal analysis, the summer relative risks were reported to be higher (9). This is not due to the actual pollutant pol·lut·ant n. Something that pollutes, especially a waste material that contaminates air, soil, or water. concentration (as BS measurements peak during the cold period in Athens), but a likely explanation may be that summer BS levels affect the average population exposure more because people spend more time outdoors and tend to keep the windows open. It seems that using the synoptic or mesoscale categories to control for weather does not affect, to any considerable extent, the estimated relative risks found for particle exposures. This is consistent with the findings of Pope and Kalkstein (13). In conclusion, in this paper we provide evidence that synoptic and mesoscale weather classification is a useful tool for studying the weather--health associations in a warm Mediterranean climate situation. The correlation between the two types of classification used here and the interactions involved need to be further investigated. REFERENCES AND NOTES (1.) Kilbourne EM. Illness due to thermal extermes. In: Maxcy-Rosenau Public Health and Preventive Medicine preventive medicine, branch of medicine dealing with the prevention of disease and the maintenance of good health practices. Until recently preventive medicine was largely the domain of the U.S. (Last JM, ed). 12th ed. New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of :Appleton-Century-Crofts, 1986;703-714. (2.) Handley BA, Webster AJ. Some factors affecting the airborne survival of bacteria outdoors. J Appl Bacteriol 79:368-378 (1995). (3.) The Eurowinter Group. Cold exposure and winter mortality from ischaemic heart disease Ischaemic (or ischemic) heart disease, or myocardial ischemia, is a disease characterized by reduced blood supply to the heart. It is the most common cause of death in most western countries. Ischaemia means a "reduced blood supply". , cerebrovascular disease cerebrovascular disease Neurology Any vascular disease affecting cerebral arteries–eg ASHD, diabetic vasculopathy, HTN, which may cause a CVA or TIA with neurologic sequelae–speech, vision, movement of variable duration. , respiratory disease, and all causes in warm and cold regions of Europe Europe is often divided into regions due to geographical, cultural or historical criteria. Some common divisions are as follows. Directional divisions Groupings by compass directions are the hardest to define in Europe, since (among other issues) the pure geographical criteria . Lancet lancet /lan·cet/ (lan´set) a small, pointed, two-edged surgical knife. lan·cet n. 349:1341-1346 (1997). (4.) Katsouyanni K, Trichopoulos D, Zavitsanos X, Touloumi G. The 1987 Athens heat wave [Letter]. Lancet 2:573 (1988). (5.) Stewart SE, Gibson B, Land G, Rackers D, Donnell HD, Grauman A. Heat-related deaths heat-related death Forensic medicine A death with a core body temperature ≥ 40.6ºC/105ºF with no other reasonable explanation of death At-risk groups Elderly, those living alone, alcoholics. See Heat wave. . Missouri 1979-1988. Morb Mortal Wkly Rep 38:437-439 (1989). (6.) Rooney C, McMichael AJ, Kovats RS, Coleman M. Excess mortality in England and Wales England and Wales are both constituent countries of the United Kingdom, that together share a single legal system: English law. Legislatively, England and Wales are treated as a single unit (see State (law)) for the conflict of laws. and in greater London Greater London: see London. during the 1995 heatwave heatwave n → ola de calor heatwave n → vague f de chaleur heatwave n → ondata di caldo . J Epidemiol Community Health 52:482-486 (1998). (7.) Kunst AE, Looman CWN CWN Catholic World News CWN Clean Water Network CWN Commonwealth Women’s Network (UK) CWN Children's Workforce Network CWN Call When Needed (helicopter services) , Mackenbach JP. Outdoor air temperature and mortality in the Netherlands: a time-series analysis Time-series analysis Assessment of relationships between two or among more variables over periods of time. . Am J Epidemiol 137:331-341 (1993). (8.) Touloumi G, Pocock SJ, Katsouyanni K, Trichopoulos D. Short-term effects of air pollution on daily mortality in Athens: a time-series analysis. Int J Epidemiol 23:957-967 (1994). (9.) Katsouyanni K, Touloumi G, Spix C, Schwartz J, Balducci F, Medina S, Rossi G, Wojtyniak B, Sunyer J, Bacharova L, et al. Short-term effects of ambient sulphur dioxide sulphur dioxide Noun Chem a strong-smelling colourless soluble gas, used in the manufacture of sulphuric acid and in the preservation of foodstuffs Noun 1. and particulate matter particulate matter n. Abbr. PM Material suspended in the air in the form of minute solid particles or liquid droplets, especially when considered as an atmospheric pollutant. Noun 1. on mortality in 12 European cities: results from time series data from the APHEA APHEA Australasian and Pacific Hansard Editors Association project. Br Med J 314:1658-1663 (1997). (10.) Steadman, RC. A universal scale of apparent temperature. J Clim Appl Meteorol 23:1674-1687 (1984). (11.) Jendritzki G, Sievers U. Human biometeorological approaches with respect to human planning. In: Proceedings of the Xth Congress of the International Society of Biometeorology The International Society of Biometeorology (ISB) is a professional society for scientists interested in biometeorology, specifically environmental and ecological aspects of the interaction of the atmosphere and biosphere. ((Driscoll D, Box EO, eds). The Hague, the Hague, The (hāg), Du. 's Gravenhage or Den Haag, Fr. La Haye, city (1994 pop. 445,279), administrative and governmental seat of the Kingdom of the Netherlands, capital of South Holland prov., W Netherlands, on the North Sea. Netherlands:SPB SPB Spb Software House SPB Saint Petersburg SPB State Personnel Board SPB Southern Pine Beetle SPB Spindle Pole Body (biology, biochemistry) SPB Special Pathogens Branch (Centers for Disease Control) Academic Publishing, 1989;25-39. (12.) Kalkstein LS. A new approach to evaluate the impact of climate on human mortality. Environ Health Perspect 96:145-150 (1991). (13.) Pope CA III CA III Challenge Athena version III (Navy SATCOM link) , Kalkstein LS. Synoptic weather modelling and estimates of the exposure-response relationship between daily mortality and particulate air pollution. Environ Health Perspect 104:414-420 (1996). (14.) Samet J, Zeger S, Kelsall J, Xu J, Kalkstein L. Does weather confound con·found tr.v. con·found·ed, con·found·ing, con·founds 1. To cause to become confused or perplexed. See Synonyms at puzzle. 2. or modify the association of particulate air pollution with mortality? Environ Res 77:9-19 (1998). (15.) Kassomenos P, Flocas HA, Lykoudis S, Petrakis M. Analysis of mesoscale patterns in relation to synoptic conditions over an urban Mediterranean basin The Mediterranean Basin refers to the lands around and surrounded by the Mediterranean Sea. In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which . Theor Appl Clim 59:215-229 (1998). (16.) Kassomenos P, Flocas HA, Lykoudis S, Skouloudis AN. Spatial and temporal characteristics of the relationship between air quality status and mesoscale atmospheric circulation over an urban Mediterranean basin. Sci Total Environ 217:37-57 (1998). (17.) Kassomenos P, Kotroni V, Kallos G. Analysis of climatological cli·ma·tol·o·gy n. The meteorological study of climates and their phenomena. cli ma·to·log and air quality observations from the greater Athens area. Atmos Environ
29B:3671-3688 (1995).(18.) Maheras P. Le Problem des Etesiens. Mediterranee 4: 57-66 (1980). (19.) Lykoudis S, Kassomenos P, Petrakis M. A method to estimate the onset of the warm period of the year. In: Proceeding of the 3rd Conference on Meteorology meteorology, branch of science that deals with the atmosphere of a planet, particularly that of the earth, the most important application of which is the analysis and prediction of weather. , Climatology climatology Branch of atmospheric science concerned with describing climate and analyzing the causes and practical consequences of climatic differences and changes. Climatology treats the same atmospheric processes as meteorology, but it also seeks to identify slower-acting and Physics of the Atmospheric Environment The envelope of air surrounding the Earth, including its interfaces and interactions with the Earth's solid or liquid surface. . Athens:National Meteorological Service, 1996;260-263. (20.) Ministry of the Environment, Planning and Public Works. Program for Air Pollution Control. Technical Report. Athens:Ministry of the Environment, Planning and Public Works, 1989. (21.) WHO. Air Quality Guidelines guidelines, n.pl a set of standards, criteria, or specifications to be used or followed in the performance of certain tasks. for Europe. Geneva Geneva, canton and city, Switzerland Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva. :World Health Organization, 1987. (22.) Katsouyanni K, Schwartz J, Spix C, Touloumi G, Zmirou D, Zanobetti A, Wojtyniak B, Vonk JM, Tobias A, Ponka A, et al. Short-term effects of air pollution on health: a European approach using epidemiologic ep·i·de·mi·ol·o·gy n. The branch of medicine that deals with the study of the causes, distribution, and control of disease in populations. [Medieval Latin epid time-series data: the APHEA protocol. J Epidemiol Community Health 50:S12-S18 (1996). (23.) Schwartz J, Spix C, Touloumi G, Bacharova L, Barumamdzadeh T, Le Tertre A, Piekarksi T, Ponce de Leon Ponce de Le·ón , Juan 1460-1521. Spanish explorer who sailed with Columbus on his second voyage (1493-1494) and discovered Florida (1513) while looking for the legendary Fountain of Youth. Noun 1. A, Rossi G, Saez M, et al. Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions. J Epidemiol Community Health 50:S3-S11 (1996). Pavlos Kassomenos,(1) Alexandros Gryparis,(2) Evangelia Samoli,(2) Klea Katsouyanni,(2) Spyros Lykoudis,(1) and Helena A. Flocas(3) (1) Laboratory of Meteorology, Department of Astrogeophysics, University of Ioannina The University of Ioannina (Greek: Πανεπιστήμιο Ιωαννίνων, Panepistimio Ioanninon) is a university lying in the plains 5 km southwest of Ioannina, Greece. , Ioannina, Greece; (2) Department of Hygiene and Epidemiology epidemiology, field of medicine concerned with the study of epidemics, outbreaks of disease that affect large numbers of people. Epidemiologists, using sophisticated statistical analyses, field investigations, and complex laboratory techniques, investigate the cause , University of Athens, Athens, Greece; (3) Laboratory of Meteorology, Department of Applied Physics, University of Athens, Athens, Greece Address correspondence to K. Katsouyanni, Department of Hygiene and Epidemiology, University of Athens, Medical School, 75 Mikras Asias Str, Athens 115 27, Greece. Telephone: 30-1-7470577. Fax: 30-1-7704225. E-mail: kkatsoug@ cc.uoa.gr Received 27 July 2000; accepted 11 December 2000. |
|
Printer friendly
Cite/link
Email
Feedback
Reader Opinion