A 10-year time-series analysis of respiratory and cardiovascular morbidity in Nicosia, Cyprus: the effect of short-term changes in air pollution and dust storms
© Middleton et al; licensee BioMed Central Ltd. 2008
Received: 25 January 2008
Accepted: 22 July 2008
Published: 22 July 2008
To date, a substantial body of research has shown adverse health effects of short-term changes in levels of air pollution. Such associations have not been investigated in smaller size cities in the Eastern Mediterranean. A particular feature in the region is dust blown from the Sahara a few times a year resulting in extreme PM10 concentrations. It is not entirely clear whether such natural phenomena pose the same risks.
The effect of changes in daily levels of particulate matter (PM10) and ozone (O3) on hospitalization for all, cardiovascular and respiratory causes in the two hospitals in Nicosia during 1 January 1995 and 30 December 2004 was investigated using generalized additive Poisson models after controlling for long- and short-term patterns as well as for the effect of weather. Meteorological records were reviewed to identify dust-storm days and analyses were repeated to quantify their effect on cardio-respiratory morbidity.
For every 10 μg/m3 increase in daily average PM10 concentrations, there was a 0.9% (95%CI: 0.6%, 1.2%) increase in all-cause and 1.2% (95%CI: -0.0%, 2.4%) increase in cardiovascular admissions. With respect to respiratory causes, an effect was observed only in the warm months. No lagged effects with levels of PM10 were observed. In contrast, positive associations with levels of ozone were only observed the two days prior to admission. These appeared stronger for cardiovascular causes and independent of the effect of PM. All-cause and cardiovascular admissions were 4.8% (95%CI: 0.7%, 9.0%) and 10.4% (95%CI: -4.7%, 27.9%) higher on dust storm days respectively. In both cases the magnitude of effect was comparable to that seen on the quartile of non-storm days with the highest levels of PM10.
We observed an increased risk of hospitalization at elevated levels of particulate matter and ozone generally consistent with the magnitude seen across several European cities. We also observed an increased risk of hospitalization on dust storm days, particularly for cardiovascular causes. While inference from these associations is limited due to the small number of dust storm days in the study period, it would appear imperative to issue health warnings for these natural events, particularly directed towards vulnerable population groups.
In the last 20 years, evidence on adverse health effects – both increased hospitalization and mortality – of elevated ambient levels of air pollutants has been accumulating [1, 2], more so recently with the use of meta-analyses of single-city time-series analyses [3, 4] or multi-city studies [5, 6]. With the major exception of the APHEA project, a multi-centre European study with a common protocol  in as many as 15 and 29 European cites in its phases I and II respectively [8–10], the majority of evidence comes from US cities e.g. the National Morbidity, Mortality and Air Pollution Study (NMMAPS) [11, 12]. While large cities in the Eastern Mediterranean, such as Athens, Tel Aviv and Istanbul were considered in APHEA, associations have not been investigated in smaller size cities where socio-economic factors (such as driving patterns, time spent outdoors and access to health care) as well as climatic conditions might vary considerably. A particular feature of the Eastern Mediterranean is episodes of re-suspended wind blown dust from desert regions, raising particle concentrations a few times a year considerably above European guidelines . It is not entirely clear whether high levels of particulate matter from such natural phenomena pose the same risks on cardiovascular and respiratory health as particles from anthropogenic sources. With PM10 concentrations comparable to the high levels seen in other much larger Southern European cities as well as frequently affected by dust storms, the capital of Cyprus, Nicosia (population approximately 270,000) offers an opportunity to address this issue. Using a time-series approach, this study investigates associations between daily levels of (a) particulate matter with aerodynamic diameter < 10 μm (PM10) on non-storm and dust storm days separately as well as (b) ozone (O3) on counts of hospital admissions for all, respiratory and cardiovascular causes during the 10-year period 1995–2004.
Data and data sources
Based on ICD code of diagnosis for inpatient admission, all cardiovascular (ICD10 codes I00–I52) and respiratory (ICD10 codes J00–J99) admissions between 1 January 1995 to 30 December 2004 (i.e. a total of 3,652 days) were obtained from the two public hospitals in Nicosia (i.e. Nicosia General and Makarios Hospital) with information on gender, age, date of admission and discharge as well as whether inpatient was resident in the district of Nicosia. The daily volume of all-cause admissions in the same period was obtained from the Cyprus Statistical Services, aggregated in 8 age- and sex-strata – males and females, aged 4 or less, 5–14, 15–64 and 65 or older. Hourly measurements of PM10 and O3 were available from two ambient air quality monitoring stations: (a) a local traffic-representative station located centrally at the Nicosia General Hospital and (b) a station reflecting background levels in the rural location of Ayia Marina, approximately 40 km from Nicosia. Continuous monitoring of coarse particles was performed with TEOM (Tapered Element Oscilling Micro-balance) instruments. Data from the rural station were available only from 1997 for ozone and 1999 for PM10, reducing the study period to 8 and 6 years respectively. Thus, the main analyses presented here were based on a single exposure series as recorded at the traffic-representative station. Completeness of the main data series of air pollutants was generally satisfactory and concurred with previous practice, including the protocol used in APHEA. Commonly, missing values are replaced using a weighted average of values from other monitoring stations on that day. With only one other station, located rurally and thus not necessarily representative of exposure in the capital, imputation of missing values was not considered not least because availability of data did not cover the full period of investigation and would replace only a small fraction of the missing values. The background station was mainly used to aid in the identification of dust-storm days, since due to its rural location it is not affected by local traffic pollution. Nevertheless, the effect on the observed estimates of using the background station to define exposure was considered in sensitivity analyses. Daily averages of air and dew point temperature, relative humidity, wind speed, precipitation and barometric pressure based on hourly measurements of Thermohygrographs (i.e. instantaneous values) were obtained from the Cyprus Meteorological Services.
Identification of dust-storm days
Dust storm events affect Cyprus at least a few days a year resulting in extreme PM concentrations, which sometimes may persist for a few consecutive days. To construct a calendar of such events, an iterative approach was used whereby starting with a pool of days (N = 773) with at least 1 hourly measurement of PM10 higher than 150 μg/m3 recorded at Nicosia Central or higher than 100 μg/m3 at the rural station (in both cases, 2 standard deviations (SD) away from the mean of hourly values on the logarithmic scale), paper-form meteorological records from the main International Airport at Larnaca (50 km from Nicosia) were reviewed to identify those days when a meteorological observer (as part of their hour-by-hour coding of weather and visibility conditions) noted poor visibility due to "dust in suspension" at any part of a given day, which did not refer to hazy conditions or dust from local sources i.e. a result of re-suspension. Candidate days were then cross-checked against a number of data-based criteria to assess the extent to which levels of PM10 on those days where indeed uncharacteristic, including (i) daily average levels of PM10 higher than 2 SDs away from the mean as recorded at the rural station, not as prone to traffic pollution and/or (ii) levels of PM10 higher than 2 SDs away from the mean in the centre of Nicosia after excluding hours of pick traffic and/or (iii) days identified as outliers (2 SDs away from the predicted value) using a predictive model of levels of PM10 based on levels the previous day and adjusting for weather variables including temperature, barometric pressure, precipitation and wind speed. The data-based criteria were not used to identify dust-storm days per se but to correct the original calendar which was based only on meteorological observations (i.e. either confirm, invalidate or propose additional days) with the main aim of categorizing days into confirmed events, where the criteria were in agreement with the meteorological observation and suspected events, where all criteria suggest an event that might have been overlooked or coded otherwise by the observer. Possible markers of dust storm events used in the past, such as low carbon monoxide levels , reduced visibility range , or based on investigation of aerosol optical depth [16, 17], were not electronically available. Finally, in accordance to previous practice [16, 18–20], backwards wind trajectories for up to 4 days ending in Cyprus (35°N, 33°E) on the day and about the time the meteorological observation was made were used to track the possible source of each identified event in the Sahara or Arabian peninsula using the National Oceanic and Atmospheric Administration (NOAA) HYSPLIT model.
Only days with at least 12 hourly measurements were used to calculate daily averages of air pollutants (PM10 and O3) as well as daily 8-hour maximum moving average for O3. The effect of changes in levels of air pollutants on the number of daily admissions was investigated in Poisson regression models (a) as linear terms, expressed as percentage increase in mean number of daily admissions per 10 μg/m3 or 10 ppb increase in levels of PM10 and O3 respectively, (b) across quartiles of increasing levels of PM10 (after including and excluding dust storm days) and O3 to assess non-linearity of effects and (c) to include a categorical variable for dust storm days and restrict the estimation of a linear effect to non-storm days only (i.e. Dust Storm Day (= 0 or 1) + PM10 daily average × [1-Dust Storm Day]). The magnitude of effect on these days was then compared to the effects seen across quartiles of all non-storm days with increasing levels of PM10. In accordance to previous practice, to ensure that extreme values of PM10 (in this case, most likely to be a result of air blown dust) would not influence the estimation of linear effects, the main analyses excluded days with average PM10 concentrations greater than 150 μg/m3 (25 days). Furthermore, to assess the extent to which associations persist at lower ambient levels of air pollution, analyses were repeated restricted to days with daily averages of PM10 less than 100 μg/m3 or 75 μg/m3 (the European standard at the time). Finally, to assess and correct for overdispersion, or extra-Poisson variation in the data, models were repeated using negative Binomial models (i.e. an overdispersed Poisson distribution). Model fit was assessed by inspection of the overdispersion parameter, the model deviance as well as patterns and magnitude of the residuals.
Generalized Additive Models (GAM) with natural splines were used to remove long-term seasonality (starting with the practical choice of 40 degrees of freedom to capture 4 seasons over the 10 year period) and penalized cubic splines to control for possible non-linear effects of the meteorological variables on the outcome (with a maximum of 5 degrees of freedom). In order to control for short-term patterns of admissions, day of the week was included in the models as a categorical variable. Before including the air pollution variables in the model, a base model was constructed to remove seasonality i.e. long-term trend and weekly patterns. Minimising the absolute value of the sum of the partial autocorrelation function was used to assess the appropriateness of the degree of smoothing. To avoid oversmoothing and, thus, eliminating patterns due to the exposure under study, windows below 2 months were generally not considered . The weather variables as well as the appropriate lags for these to include in the models were then chosen by minimizing the Unbiased Risk Estimator (UBRE) and/or the Akaike's Information Criterion (AIC). All models were checked for remaining autocorrelation by examining plots of the partial autocorrelation function and, if necessary, sensitivity of the inferences was assessed in autoregressive Poisson models. The final model controlled for long- and short-term trend, temperature on the same day as well as the two previous days (lags 1 and 2) and relative humidity on the same day. Wind speed, precipitation and barometric pressure were not considered as confounders of the association between air pollutants and hospitalization. The effect of ozone was assessed before and after controlling for the effect of PM10.
Same-day and lagged exposure (up to 2 previous days) were considered. Due to lack of statistical power, distributed lag models were not considered . Similarly, due to the small number of daily cause-specific admissions, analyses were only stratified by gender (all ages combined) or age (i.e. younger/older than 15 years of age). Models were repeated to include interaction terms between levels of pollutants and season to investigate evidence for effect modification either (a) during cold and warm months indexed by monthly average temperature levels or (b) on days when average daily temperature was higher or lower than 20 or 30°. Finally, where possible (i.e. cause-specific investigation), all analyses were repeated to exclude non-Nicosia residents since these may represent transfers from other hospitals and, as such, can dilute any effect since day of admission may not accurately reflect day of exposure. Data manipulation was performed in STATA SE 9.0. Analyses were performed using the MGCV package in the R software (R 2.2.0).
Summary statistics for daily number of admissions, levels of air pollutants and meteorological factors in the 10-year period 1 Jan 1995–30 Dec 2004 (n = 3652 days).
A. Daily number of hospital admissions for all, cardiovascular and respiratory causes
Total number (% Nicosia residents)1
10 896 (75%)
14 827 (86%)
B. Levels of air pollutants, shown separately for cold and warm months 3
Number of Days (% of total days)4
PM10 24-hour average (μg/m3)
O3 8-hour MA max (ppb)
Ayia Marina 5
PM10 24-hour average (μg/m3)
O3 8-hour MA max (ppb)
C. Meteorological factors
Table 1 also shows the distribution of daily 24-hour average concentrations of PM10 and daily maximum 8-hour moving average of O3 as measured at either station as well as daily averages of the meteorological factors considered in the models. In addition to 354 (9.7%) and 387 (10.6%) days for which no PM10 and O3 were recorded at the central station respectively, an additional 81 (2.2%) and 57 (1.6%) days were excluded from the analyses as only fewer than 12 hourly measurements were available. Similarly, for the background station, around 15% of days were excluded. Daily mean levels of PM10 in Nicosia Central ranged from 5.0 to 1370.6 μg/m3 (interquartile range: 40.0–64.1) with, as expected, slightly higher concentrations during the colder months. In the rural station, levels of PM10 ranged from 6.3 to 952.4 μg/m3 (interquartile range: 17.0–36.3) and, in contrast to the pattern observed in the central station, appeared lower during the cold season since winter levels are mainly influenced by local sources. With the exception of extreme values thought to be the result of dust storms, levels of air pollutants in Nicosia were comparable to those seen in many southern European cities and exceeded the European standard of 75 μg/m3 (at the time) between 11–57 days a year. The maximum 8-hour moving average for ozone ranged between 3.7 and 71.1 ppb (interquartile range: 26.0–48.0) in Nicosia and 28.9 and 78.7 ppb (interquartile range: 43.2–57.0) in Ayia Marina.
Percentage increase (and 95% CI) in admissions after adjusting for long- and short-term patterns as well as the effect of weather per 10 μg/m3 increase in PM10 and 10 ppb increase in O3 concentrations in Nicosia Central.
A. Per 10 μg/m3increase in daily 24-hour average PM10 4
Cardiovascular + Respiratory
All age/sex groups
B. Per 10 ppb increase in daily maximum 8-hour moving average O 3
Cardiovascular + Respiratory
All age/sex groups
Differential effects of a 10 μg/m3 increase in PM10 on respiratory admissions during the cold and warm season after adjusting for long- and short-term patterns as well as the effect of weather.
Percentage increase (and 95% CI) per 10 μg/m3 increase in PM10 1
P-value for effect modification
All age/sex groups
Calendar of confirmed and suspected dust-storm events as identified by either a meteorology observer at Larnaca airport and/or uncharacteristic levels of PM10.
Number of days
Max number of consecutive days
7 Feb#, 8 Feb, 9 Feb
22 Apr*, 8 Dec
16 Mar, 27 Mar, 28 Mar, 5 Jul
17 Feb*, 19 Mar, 30 Mar, 7 May
4 Apr#, 5 Apr#, 6 Apr#, 13 Apr, 18 Apr, 19 Apr, 18 Nov, 30 Dec*
27 Feb*, 28 Feb*, 1 Mar, 18 Apr, 19 Apr, 22 Apr, 1 May, 13 May
31 Mar*, 5 Apr, 6 Apr, 15 Apr, 1 Oct*, 19 Oct, 20 Oct, 10 Nov
13 Jan, 2 Feb, 18 Feb*, 2 Mar*, 18 Mar, 19 Mar, 3 Apr, 4 Apr, 5 Apr, 6 Apr, 17 Apr*, 24 Apr, 29 May, 30 May, 11 Sept, 17 Sept
16 Jan, 22 Jan#, 5 Mar, 27 Mar, 7 May, 10 May, 26 Oct#, 27 Oct#
For comparison purposes, figure 5 also presents the percentage increase in admissions across quartiles of non-storm days with increasing levels of PM10 after adjustments for seasonality and the confounding effect of weather. Stepwise increases were observed for all and cardiovascular causes, with 5.4% (95%CI: 3.6%, 7.2%) and 7.1% (95%CI 0.1%, 14.6%) increased admissions respectively in the quartile of days with the highest levels of PM10 (>64 μg/m3) compared to the quartile of days with the lowest levels (PM10 < 40 μg/m3); in both cases, p-value for linear trend < 0.01. This was not the case with respiratory admissions, where the risk of admissions rose by 2.4% (95%CI: -3.0%, 8.2%), 4.2% (95%CI: -1.5%, 10.2%) and 2.8% (95%CI: -2.8%, 8.8%) across quartiles, at least partly explaining the lack of an overall linear association. In all cases, however, the magnitude of effects on dust-storm days appeared at least comparable to the effects seen on non-storm days with the highest PM levels.
Short-term changes in PM10 increase the risk of same-day hospitalization for all-cause and cardiovascular causes in Nicosia hospitals. An effect on respiratory health was observed only during the warm season. In contrast to the effects seen with same-day levels of PM10, only lagged effects were observed with levels of ozone. These associations appeared independent of the effect of levels of PM10 and, perhaps, stronger for cardiovascular causes. More interestingly, there was also evidence to suggest that risk of hospitalization was higher on dust storm days. While a statistically significant association was observed only for overall admissions, in all cases, effects were at least comparable in magnitude to those seen on non-storm days with the highest levels of PM10, particularly for cardiovascular causes.
Several studies have shown that the effect of air pollution on hospitalization is stronger for certain cardio-respiratory conditions  and among certain sub-groups of the population, such as children, the elderly or people with a recent history [25–28]. The small number of daily events in a city the size of Nicosia provides limited statistical power to permit a finer age-, sex, or cause-specific analysis. This is, in fact, portrayed in the often low precision of the estimates and, thus, wide confidence intervals. Furthermore, multiple testing across sub-groups or different lags might produce some spurious associations. For this reason, the sub-group analyses were a priori restricted to gender (only)- and age (only)-specific comparisons and lagged exposure for up to 2 days. Due to lack of statistical power in a small sample, distributed lag models were not considered. Models investigating effect modification and non-linear effects across quartiles are only complimentary to the main analysis, nevertheless necessary, in the first case to highlight important differences by season and, in the case of the latter, to provide a basis of comparison (and a similar unit of measurement) between dust storm and non-storm days. The observed patterns appear not only internally consistent but, as a result of the long period of investigation (i.e. 10-years), the magnitude of estimates in a small city the size of Nicosia seem to be in agreement with those observed in large studies elsewhere.
As with all hospital data, there might be to some extent misclassification of the cause of admission, particularly in people with both respiratory and cardiovascular pathologies. However, it is unlikely that such misclassification is temporally related to levels of air pollutants and, thus, can only bias our estimates towards the null. With only one air quality station in Nicosia in operation for the full 10-year period of investigation, the analyses presented here are based on a single exposure series. Thus, replacing missing values in about 10% of days (and an additional 2–3% days purposefully excluded due to availability of less than 12 hourly measurements) was not possible. Nevertheless, the data series is generally longer than in similar time-series studies. Furthermore, similar patterns were observed when analyses were repeated for the reduced period for which data were available from the background station. Finally, identification of dust-storm days was mainly based on visibility observations and coding practices of a meteorological observer. Subjective in nature as it may be, a series of data-based criteria were used to validate the observations. It is likely that some dust storms, especially those of milder intensity, might have been missed out. However, it is unlikely that days with high levels of PM solely due to traffic sources were considered as dust-storm days. At any rate, the observed effect persisted when restricting inferences to the group of days for which meteorological observations and measurements at the three sites were in agreement.
The effect of short-term changes in air pollutants on hospitalisation
Even though at limited power due to the small number of daily events in a city the size of Nicosia, the long period of investigation has allowed for some positive (and statistically significant) associations between levels of particulate matter and risk of hospitalization to be observed. Estimates seem consistent with the size of effects seen across several European cities, particularly for cardiovascular causes (i.e. 0.4%–1.4% per 10 μg/m3 increase in PM) [29, 30]. Surprisingly, other than the warm season, no overall effect was observed with respiratory admissions. While several studies have shown associations between levels of PM and respiratory mortality [6, 10], there have been some inconsistent results in the case of hospital admissions , with some studies only showing associations in certain sub-groups  or for certain respiratory causes, such as COPD and asthma . Furthermore, admissions during the colder months are mainly driven by viral respiratory infections. Even though models adjusted for the observed seasonal pattern with higher respiratory admissions in the colder season, it is possible that not explicitly controlling for these causes (due to lack of data) has masked a possible effect in the colder months, particularly in children (aged less than 15). It is also important to note that, in the case of respiratory admissions, a striking weakly pattern was observed with a large dip in admissions on Tuesdays (2 daily admissions on average) on either side of high volume on Mondays and Wednesdays (9 daily admissions). With the exception of the elderly (aged 65+), similar patterns were observed in all age and sex groups. While it was not clear whether this was due to reduced bed availability, there was some indication that people admitted on Monday were more likely to be discharged before Wednesday (42.5%) while those admitted on Wednesday were more likely to be kept until the following Monday (as many as 37% and only 13% for any longer). The extent to which this atypical weekly pattern has produced a discrepancy between actual need and admission and, thus, contributed to the lack of any strong association with overall respiratory admissions is not known.
No positive effects were observed with levels of PM10 the 2 previous days. While lagged or cumulative effects have commonly been observed between levels of PM and mortality in several studies , it is not uncommon for the strongest associations to be observed with same-day levels in the case of hospital admissions [12, 35]. Perhaps, even more so in the case of Cypriot cities where, with no referral system, direct access to specialist health care may be considerably easier than in larger European or US cities. A number of person-based studies have now used average levels of air pollutants the 24 hours preceding an event (rather than same calendar day which would include hours after as well as before the event) and, at least amongst susceptible populations, have shown effects in as little as 6 hours prior to an arrhythmia and even 2 hours prior to a myocardial infarction [36–39].
In contrast to the same-day association with levels of PM, only effects of lagged exposure to ozone were observed. Negative associations with same-day levels of ozone have previously been observed in several of the 23 APHEA cities, an effect which persisted even in the summer period in at least 4 of the cities, namely Rome, Paris, Tel Aviv and Valencia . While explanations for this are not clear, it is thought to be a product of the relationship between ozone (a secondary pollutant produced by photochemical reactions) and traffic-related primary pollutants such as nitrogen oxides (NO) and volatile organic compounds (VOC) which can reduce ozone concentrations at least at the local scale. Thus, high ozone concentrations in stations located in central parts of cities, such as in this case, may reflect low levels of local traffic pollutants or good dispersion conditions, which can lead to negative associations with health indicators, at least in the short-run, whereas it is common for stronger associations with ozone to be subsequently observed at lagged intervals. A similar pattern of negative same-day associations, albeit much weaker, was observed with levels of ozone as recorded at the rural station, not influenced by local pollution. Finally, while, there have generally been some inconsistent findings for the association between cardiovascular morbidity and levels of ozone, with some reporting positive , no or even negative associations , effects of a similar magnitude have been previously reported between levels of ozone two days before admission for cardiovascular causes in London . In general, neither the fact that stronger associations with lagged rather than concurrent exposure nor that stronger effects for cardiovascular than respiratory admissions were observed seem inconsistent with previous findings [43–45].
Effect modification by season
Seasonal differential effects of changes in levels of air pollution on the risk of hospitalization have been previously reported, particularly with respects to stronger effects of PM on respiratory health during the warm season such as those observed here [32, 43, 46]. Other studies, however, have found little evidence of differential effects by season [47, 48]. It is uncertain whether such differential effects carry biological plausibility, i.e. a synergistic effect of air pollution and temperature amplifying people's response to lower levels of air pollutants than normally, or it simply, reflects an increased proportion of time spent outdoors, and thus higher exposure, on warm days . In APHEA, for instance, the stronger effects of PM10 on total mortality observed in the warmer than colder cities persisted when latitude was used instead of actual temperature, thus, it was proposed that ambient measurements in warmer places may represent the average population exposure more accurately than in colder places where people do not spend as much time outdoors . Here, other than some weak evidence of strongest effects on cardio-respiratory morbidity on the warmest days (>30°), generally, more pronounced differential effects were observed across cold-warm months rather than across cold-warm days (based on daily mean temperature).
In the light of evidence of ozone effects on mortality restricted to the warm season across 23 APHEA cities, the stronger association between cardiovascular admissions and ozone during the colder season observed here appears surprising . However, some similar patterns have been observed elsewhere, particularly amongst the elderly ; possible explanations for this pattern are unclear and it might simply be a chance finding. Nonetheless, in a recent cross-sectional study in Korea, it was reported that measures of blood pressure, a risk factor for cardiovascular disease, were significantly associated with PM10 levels only in the warm season while the reverse was true for O3, with associations only during the cold season .
The effect of dust storms
Long-range transport of Saharan dust across the Mediterranean into southern Europe [52, 53], and less frequently as far north as the British Isles , is well established. Consistent with a recent examination of these events , our analysis also suggests that there has been a rise in their frequency, at least half of which seem to occur during the spring months and can last for as many as four consecutive days. Unlike the mineral and chemical composition as well as transport patterns of Saharan dust, the possible health effects of these natural events have not been extensively studied. There is some modest evidence from Taiwan and Korea of adverse effects of wind-blown dust from the Mongolia/China desert on both cardiovascular and respiratory health, some times lasting for up 3 days after the event [55–57]; reported associations were, however, not always statistically significant.
In contrast, a study of 17 episodes with a high concentration of coarse (crustal-derived) but not fine particles during a six-year period in Spokane, Washington, revealed no evidence of an increased risk of death on dust days . Similarly, an investigation into an unusual event of transported dust over the Atlantic to Greater Vancouver, Canada, has shown no effect on hospital admissions . Some studies have, in fact, reported strengthening of the observed health effects when windblown dust days were excluded from the analyses  or reduced health effects on windy days , in both cases suggestive that crustal-derived particles are more benign that those from anthropogenic processes. In our analyses, we have not observed an attenuation of effects by including dust-storm days. On the contrary, we found evidence of increased admissions on dust-storm days of similar magnitude to the effects seen on non-storm days with the highest concentrations. Of course, the possibility of air-borne dust containing particles of anthropogenic sources can not be excluded since mega-cities, such as Cairo, are commonly on the path of these events. Alternatively, some support for the adverse effects of particles due to natural sources observed here comes from a recent study of the biological content in dust transferred to Haifa, Israel during similar events in 2004–2005 that revealed both an increase in the concentration of airborne microorganisms and a change in the usual content of fungal population in PM samples, both which are thought to affect human health . Similar findings have been reported from aeromicrobiological analyses of samples on the Turkish coastal town of Erdemli .
We observed an increased risk of hospitalization at elevated levels of particulate matter and ozone generally consistent with the magnitude seen across several European cities. Interestingly, we also observed an increased risk of hospitalization on dust storm days, particularly for cardiovascular causes. While inference from these associations is limited due to the small number of dust storm days in the study period, these effects did not appear to be an artifact of including days of high traffic pollution. While these represent non-preventable events, with a magnitude of effects at least comparable to those on days with the highest levels of PM10 from traffic sources, such events may merit special health warnings directed to the most vulnerable population groups.
List of abbreviations
- μg/m3 :
Micrograms per cubic metre
Akaike information criterion
The Air Pollution and Health: a European Approach Project
International Classification of Diseases
Hybrid Single-Particle Lagrangian Integrated Trajectory
Generalized Additive Models
The National Morbidity, Mortality and Air Pollution Study
National Oceanic and Atmospheric Administration
- O3 :
- PM10 :
Particulate matter with aerodynamic diameter less than 10 microns
parts per billion
Tapered Element Oscilling Micro-balance
Unbiased Risk Estimator.
We wish to acknowledge the Cyprus Ministry of Health for financial assistance for this project. Also, the Cyprus Statistical Services, the Air Quality Section (Cyprus Ministry of Labour) and the Meteorological Services of Cyprus for providing us with the admissions, air pollution and meteorological data respectively. In particular, Mr Stelios Pashiardis (Meteorological Services) for the support and helpful discussions. Finally, Dr Meredith Franklin for advice on statistical matters.
- Wilson AM, Salloway JC, Wake CP, Kelly T: Air pollution and the demand for hospital services: A review. Environ Int. 2004, 30 (8): 1109-1118. 10.1016/j.envint.2004.01.004.View ArticleGoogle Scholar
- Pope CA, Dockery DW: Health effects of fine particulate air pollution: Lines that connect. J Air Waste Manage Assoc. 2006, 56 (6): 709-742.View ArticleGoogle Scholar
- Levy JI, Hammitt JK, Spengler JD: Estimating the mortality impacts of particulate matter: What can be learned from between-study variability?. Environ Health Perspect. 2000, 108 (2): 109-117. 10.2307/3454508.View ArticleGoogle Scholar
- Bell ML, Dominici F, Samet JM: A meta-analysis of time-series studies of ozone and mortality with comparison to the national morbidity, mortality, and air pollution study. Epidemiology. 2005, 16 (4): 436-445. 10.1097/01.ede.0000165817.40152.85.View ArticleGoogle Scholar
- Ballester F, Saez M, Perez-Hoyos S, Iniguez C, Gandarillas A, Tobias A, Bellido J, Taracido M, Arribas F, Daponte A, Alonso E, Canada A, Guillen-Grima F, Cirera L, Perez-Boillos MJ, Saurina C, Gomez F, Tenias JM: The EMECAM project: a multicentre study on air pollution and mortality in Spain: combined results for particulates and for sulfur dioxide. Occup Environ Med. 2002, 59 (5): 300-308. 10.1136/oem.59.5.300.View ArticleGoogle Scholar
- Le Tertre A, Quenel P, Eilstein D, Medina S, Prouvost H, Pascal L, Boumghar A, Saviuc P, Zeghnoun A, Filleul L, Declercq C, Cassadou S, Le Goaster C: Short-term effects of air pollution on mortality in nine French cities: A quantitative summary. Arch Environ Health. 2002, 57 (4): 311-319.View ArticleGoogle Scholar
- Katsouyanni K, Zmirou D, Spix C, Sunyer J, Schouten JP, Ponka A, Anderson HR, Lemoullec Y, Wojtyniak B, Vigotti MA, Bacharova L: Short-Term Effects of Air-Pollution on Health - a European Approach Using Epidemiologic Time-Series Data - the Aphea Project - Background, Objectives, Design. Eur Respir J. 1995, 8 (6): 1030-1038.Google Scholar
- Aga E, Samoli E, Touloumi G, Katsouyanni K: Ambient particulate matter (PM10) concentrations and cause-specific mortality in 28 European cities: Results from the APHEA2 project. Epidemiology. 2001, 12 (4): S71-S71.Google Scholar
- Touloumi G, Atkinson R, Le Tertre A, Samoli E, Schwartz J, Schindler C, Vonk JM, Rossi G, Saez M, Rabszenko D, Katsouyanni K: Analysis of health outcome time series data in epidemiological studies. Environmetrics. 2004, 15 (2): 101-117. 10.1002/env.623.View ArticleGoogle Scholar
- Analitis A, Katsouyanni K, Dimakopoulou K, Samoli E, Nikoloulopoulos AK, Petasakis Y, Touloumi G, Schwartz J, Anderson HR, Cambra K, Forastiere F, Zmirou D, Vonk JM, Clancy L, Kriz B, Bobvos J, Pekkanen J: Short-term effects of ambient particles on cardiovascular and respiratory mortality. Epidemiology. 2006, 17 (2): 230-233. 10.1097/01.ede.0000199439.57655.6b.View ArticleGoogle Scholar
- Dominici F, McDermott A, Daniels M, Zeger SL, Samet JM: Revised analyses of the National Morbidity, Mortality, and Air Pollution Study: Mortality among residents of 90 cities. J Toxicol Environ Health Part A. 2005, 68 (13-14): 1071-1092. 10.1080/15287390590935932.View ArticleGoogle Scholar
- Dominici F, Peng RD, Bell ML, Pham L, McDermott A, Zeger S, Samet JM: Fine particulate air pollution and hospital admissions for cardiovascular and respiratory diseases. JAMA. 2006, 295 (10): 1127-1134. 10.1001/jama.295.10.1127.View ArticleGoogle Scholar
- Goudie AS, Middleton NJ: Saharan dust storms: nature and consequences. Earth Sci Rev. 2001, 56 (1-4): 179-204. 10.1016/S0012-8252(01)00067-8.View ArticleGoogle Scholar
- Schwartz J, Norris G, Larson T, Sheppard L, Claiborne C, Koenig J: Episodes of high coarse particle concentrations are not associated with increased mortality. Environ Health Perspect. 1999, 107 (5): 339-342. 10.2307/3434536.View ArticleGoogle Scholar
- Gyan K, Henry W, Lacaille S, Laloo A, Lamsee-Ebanks C, McKay S, Antoine RM, Monteil MA: African dust clouds are associated with increased paediatric asthma accident and emergency admissions on the Caribbean island of Trinidad. Int J Biometeorol. 2005, 49 (6): 371-376. 10.1007/s00484-005-0257-3.View ArticleGoogle Scholar
- Balis D, Amiridis V, Kazadzis S, Papayannis A, Tsaknakis G, Tzortzakis S, Kalivitis N, Vrekoussis M, Kanakidou M, Mihalopoulos N, Chourdakis G, Nickovic S, Perez C, Baldasano J, Drakakis M: Optical characteristics of desert dust over the East Mediterranean during summer: a case study. Ann Geophys. 2006, 24 (3): 807-821.View ArticleGoogle Scholar
- Toledano C, Cachorro VE, de Frutos AM, Sorribas M, Prats N, de la Morena BA: Inventory of African desert dust events over the southwestern Iberian Peninsula in 2000-2005 with an AERONET Cimel Sun photometer. J Geophys Res [Atmos]. 2007, 112 (D21):
- Lee BK, Lee HK, Jun NY: Analysis of regional and temporal characteristics of PM10 during an Asian dust episode in Korea. Chemosphere. 2006, 63 (7): 1106-1115. 10.1016/j.chemosphere.2005.09.001.View ArticleGoogle Scholar
- Schlesinger P, Mamane Y, Grishkan I: Transport of microorganisms to Israel during Saharan dust events. Aerobiologia. 2006, 22 (4): 259-273. 10.1007/s10453-006-9038-7.View ArticleGoogle Scholar
- Zabalza J, Ogulei D, Elustondo D, Santamaria JM, Alastuey A, Querol X, Hopke PK: Study of urban atmospheric pollution in Navarre (Northern Spain). Environ Monit Assess. 2007, 134 (1-3): 137-151. 10.1007/s10661-007-9605-6.View ArticleGoogle Scholar
- Katsouyanni K, Touloumi G, Samoli E, Gryparis A, Le Tertre A, Monopolis Y, Rossi G, Zmirou D, Ballester F, Boumghar A, Anderson HR, Wojtyniak B, Paldy A, Braunstein R, Pekkanen J, Schindler C, Schwartz J: Confounding and effect modification in the short-term effects of ambient particles on total mortality: Results from 29 European cities within the APHEA2 project. Epidemiology. 2001, 12 (5): 521-531. 10.1097/00001648-200109000-00011.View ArticleGoogle Scholar
- Schwartz J: The distributed lag between air pollution and daily deaths. Epidemiology. 2000, 11 (3): 320-326. 10.1097/00001648-200005000-00016.View ArticleGoogle Scholar
- Middleton NJ, Goudie AS: Saharan dust: sources and trajectories. Trans Inst Br Geogr. 2001, 26 (2): 165-181. 10.1111/1475-5661.00013.View ArticleGoogle Scholar
- Zanobetti A, Schwartz J: The effect of particulate air pollution on emergency admissions for myocardial infarction: A multicity case-crossover analysis. Environ Health Perspect. 2005, 113 (8): 978-982.View ArticleGoogle Scholar
- Morgan G, Corbett S, Wlodarczyk J: Air pollution and hospital admissions in Sydney, Australia, 1990 to 1994. Am J Public Health. 1998, 88 (12): 1761-1766.View ArticleGoogle Scholar
- Zanobetti A, Schwartz J, Gold D: Are there sensitive subgroups for the effects of airborne particles?. Environ Health Perspect. 2000, 108 (9): 841-845. 10.2307/3434991.View ArticleGoogle Scholar
- Sunyer J, Ballester F, Le Tertre A, Atkinson R, Ayres JG, Forastiere F, Forsberg B, Vonk JM, Bisanti L, Tenias JM, Medina S, Schwartz J, Katsouyvanni K: The association of daily sulfur dioxide air pollution levels with hospital admissions for cardiovascular diseases in Europe (The Aphea-II study). Eur Heart J. 2003, 24 (8): 752-760. 10.1016/S0195-668X(02)00808-4.View ArticleGoogle Scholar
- Arena VC, Mazumdar S, Zborowski JV, Talbott EO, He S, Chuang YH, Schwerha JJ: A retrospective investigation of PM10 in ambient air and cardiopulmonary hospital admissions in Allegheny County, Pennsylvania: 1995-2000. J Occup Environ Med. 2006, 48 (1): 38-47. 10.1097/01.jom.0000183096.20678.f1.View ArticleGoogle Scholar
- Le Tertre A, Medina S, Samoli E, Forsberg B, Michelozzi P, Boumghar A, Vonk JM, Bellini A, Atkinson R, Ayres JG, Sunyer J, Schwartz J, Katsouyanni K: Short-term effects of particulate air pollution on cardiovascular diseases in eight European cities. J Epidemiol Community Health. 2002, 56 (10): 773-779. 10.1136/jech.56.10.773.View ArticleGoogle Scholar
- Larrieu S, Jusot JF, Blanchard M, Prouvost H, Declercq C, Fabre P, Pascal L, Le Tertre A, Wagner V, Riviere S, Chardon B, Borrelli D, Cassadou S, Eilstein D, Lefranc A: Short term effects of air pollution on hospitalizations for cardiovascular diseases in eight French cities: The PSAS program. Sci Total Environ. 2007, 387 (1-3): 105-112. 10.1016/j.scitotenv.2007.07.025.View ArticleGoogle Scholar
- Fusco D, Forastiere F, Michelozzi P, Spadea T, Ostro B, Arca M, Perucci CA: Air pollution and hospital admissions for respiratory conditions in Rome, Italy. Eur Respir J. 2001, 17 (6): 1143-1150. 10.1183/09031936.01.00005501.View ArticleGoogle Scholar
- Anderson HR, Bremner SA, Atkinson RW, Harrison RM, Walters S: Particulate matter and daily mortality and hospital admissions in the west midlands conurbation of the United Kingdom: associations with fine and coarse particles, black smoke and sulphate. Occup Environ Med. 2001, 58 (8): 504-510. 10.1136/oem.58.8.504.View ArticleGoogle Scholar
- Atkinson RW, Anderson HR: Acute effects of particulate air pollution on respiratory admissions - Results from the APHEA 2 project. Epidemiology. 2001, 12 (4): S54-S54.Google Scholar
- Zanobetti A, Schwartz J, Samoli E, Gryparis A, Touloumi G, Peacock J, Anderson RH, Le Tertre A, Bobros J, Celko M, Goren A, Forsberg B, Michelozzi P, Rabczenko D, Hoyos SP, Wichmann HE, Katsouyanni K: The temporal pattern of respiratory and heart disease mortality in response to air pollution. Environ Health Perspect. 2003, 111 (9): 1188-1193.View ArticleGoogle Scholar
- Schwartz J: Air pollution and hospital admissions for heart disease in eight US counties. Epidemiology. 1999, 10 (1): 17-22.View ArticleGoogle Scholar
- Luttmann-Gibson H, Rich D, Link M, Gold D, Mittleman M, Schwartz J, Verrier R, Dockery D: Risk of cardiac arrhythmias among implanted cardioverter defibrillator patients associated with six-hour air pollution exposures. Epidemiology. 2003, 14 (5): S41-S42.View ArticleGoogle Scholar
- Peters A, Dockery DW, Muller JE, Mittleman MA: Increased particulate air pollution and the triggering of myocardial infarction. Circulation. 2001, 103 (23): 2810-2815.View ArticleGoogle Scholar
- Dockery DW, Luttmann-Gibson H, Rich DQ, Link MS, Mittleman MA, Gold DR, Koutrakis P, Schwartz JD, Verrier RL: Association of air pollution with increased incidence of ventricular tachyarrhythmias recorded by implanted cardioverter defibrillators. Environ Health Perspect. 2005, 113 (6): 670-674.View ArticleGoogle Scholar
- Rich DQ, Schwartz J, Mittleman MA, Link M, Luttmann-Gibson H, Catalano PJ, Speizer FE, Dockery DW: Association of short-term ambient air pollution concentrations and ventricular arrhythmias. Am J Epidemiol. 2005, 161 (12): 1123-1132. 10.1093/aje/kwi143.View ArticleGoogle Scholar
- Gryparis A, Forsberg B, Katsouyanni K, Analitis A, Touloumi G, Schwartz J, Samoli E, Medina S, Anderson HR, Niciu EM, Wichmann HE, Kriz B, Kosnik M, Skorkovsky J, Vonk JM, Dortbudak Z: Acute effects of ozone on mortality from the "Air pollution and health: A European approach" project. Am J Respir Crit Care Med. 2004, 170 (10): 1080-1087. 10.1164/rccm.200403-333OC.View ArticleGoogle Scholar
- Koken PJM, Piver WT, Ye F, Elixhauser A, Olsen LM, Portier CJ: Temperature, air pollution, and hospitalization for cardiovascular diseases among elderly people in Denver. Environ Health Perspect. 2003, 111 (10): 1312-1317.View ArticleGoogle Scholar
- Prescott GJ, Cohen GR, Elton RA, Fowkes FGR, Agius RM: Urban air pollution and cardiopulmonary ill health: a 14.5 year time series study. Occup Environ Med. 1998, 55 (10): 697-704.View ArticleGoogle Scholar
- Atkinson RW, Bremner SA, Anderson HR, Strachan DP, Bland JM, de Leon AP: Short-term associations between emergency hospital admissions for respiratory and cardiovascular disease and outdoor air pollution in London. Arch Environ Health. 1999, 54 (6): 398-411.View ArticleGoogle Scholar
- Bell ML, McDermott A, Zeger SL, Samet JM, Dominici F: Ozone and short-term mortality in 95 US urban communities, 1987-2000. JAMA. 2004, 292 (19): 2372-2378. 10.1001/jama.292.19.2372.View ArticleGoogle Scholar
- Ballester F, Rodriguez P, Iniguez C, Saez M, Daponte A, Galan I, Taracido M, Arribas F, Bellido J, Cirarda FB, Canada A, Guillen JJ, Guillen-Grima F, Lopez E, Perez-Hoyos S, Lertxundi A, Toro S: Air pollution and cardiovascular admissions association in Spain: results within the EMECAS project. J Epidemiol Community Health. 2006, 60 (4): 328-336. 10.1136/jech.2005.037978.View ArticleGoogle Scholar
- Ren CZ, Tong SL: Temperature modifies the health effects of particulate matter in Brisbane, Australia. Int J Biometeorol. 2006, 51 (2): 87-96. 10.1007/s00484-006-0054-7.View ArticleGoogle Scholar
- Samet J, Zeger S, Kelsall J, Xu J, Kalkstein L: Does weather confound or modify the association of particulate air pollution with mortality? An analysis of the Philadelphia data, 1973-1980. Environ Res. 1998, 77 (1): 9-19. 10.1006/enrs.1997.3821.View ArticleGoogle Scholar
- Schwartz J: Assessing confounding, effect modification, and thresholds in the association between ambient particles and daily deaths. Environ Health Perspect. 2000, 108 (6): 563-568. 10.2307/3454620.View ArticleGoogle Scholar
- Katsouyanni K: Health-Effects of Air-Pollution in Southern Europe - Are There Interacting Factors. Environ Health Perspect. 1995, 103: 23-27. 10.2307/3432445.View ArticleGoogle Scholar
- Anderson HR, Atkinson RW: Ozone and daily respiratory hospital admissions in 8 European cities. Results from APHEA 2. Epidemiology. 2001, 12 (4): S56-S56.Google Scholar
- Choi JH, Xu QS, Park SY, Kim JH, Hwang SS, Lee KH, Lee HJ, Hong YC: Seasonal variation of effect of air pollution on blood pressure. J Epidemiol Community Health. 2007, 61 (4): 314-318. 10.1136/jech.2006.049205.View ArticleGoogle Scholar
- Rodriguez S, Querol X, Alastuey A, Kallos G, Kakaliagou O: Saharan dust contributions to PM10 and TSP levels in Southern and Eastern Spain. Atmos Environ. 2001, 35 (14): 2433-2447. 10.1016/S1352-2310(00)00496-9.View ArticleGoogle Scholar
- Gerasopoulos E, Kouvarakis G, Babasakalis P, Vrekoussis M, Putaud JP, Mihalopoulos N: Origin and variability of particulate matter (PM10) mass concentrations over the Eastern Mediterranean. Atmos Environ. 2006, 40 (25): 4679-4690. 10.1016/j.atmosenv.2006.04.020.View ArticleGoogle Scholar
- Ryall DB, Derwent RG, Manning AJ, Redington AL, Corden J, Millington W, Simmonds PG, O'Doherty S, Carslaw N, Fuller GW: The origin of high particulate concentrations over the United Kingdom, March 2000. Atmos Environ. 2002, 36 (8): 1363-1378. 10.1016/S1352-2310(01)00522-2.View ArticleGoogle Scholar
- Kwon HJ, Cho SH, Chun Y, Lagarde F, Pershagen G: Effects of the Asian dust events on daily mortality in Seoul, Korea. Environ Res. 2002, 90 (1): 1-5. 10.1006/enrs.2002.4377.View ArticleGoogle Scholar
- Chen YS, Sheen PC, Chen ER, Liu YK, Wu TN, Yang CY: Effects of Asian dust storm events on daily mortality in Taipei, Taiwan. Environ Res. 2004, 95 (2): 151-155. 10.1016/j.envres.2003.08.008.View ArticleGoogle Scholar
- Chen YS, Yang CY: Effects of Asian dust storm events on daily hospital admissions for cardiovascular disease in Taipei, Taiwan. J Toxicol Environ Health Part A. 2005, 68 (17-18): 1457-1464. 10.1080/15287390590967388.View ArticleGoogle Scholar
- Bennett CM, McKendry IG, Kelly S, Denike K, Koch T: Impact of the 1998 Gobi dust event on hospital admissions in the Lower Fraser Valley, British Columbia. Sci Total Environ. 2006, 366 (2-3): 918-925. 10.1016/j.scitotenv.2005.12.025.View ArticleGoogle Scholar
- Pope CA, Hill RW, Villegas GM: Particulate air pollution and daily mortality on Utah's Wasatch Front. Environ Health Perspect. 1999, 107 (7): 567-573. 10.2307/3434399.View ArticleGoogle Scholar
- Ostro BD, Broadwin R, Lipsett MJ: Coarse and fine particles and daily mortality in the Coachella Valley, California: a follow-up study. J Exposure Anal Environ Epidemiol. 2000, 10 (5): 412-419. 10.1038/sj.jea.7500094.View ArticleGoogle Scholar
- Griffin DW, Kubilay N, Kocak M, Gray MA, Borden TC, Shinn EA: Airborne desert dust and aeromicrobiology over the Turkish Mediterranean coastline. Atmos Environ. 2007, 41 (19): 4050-4062. 10.1016/j.atmosenv.2007.01.023.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.