Comparing ozone metrics on associations with outpatient visits for respiratory diseases in Taipei Metropolitan area

Comparison of the association between different ozone indicators and daily respiratory hospitalization in Guangzhou, China

Background

Epidemiological studies have widely proven the impact of ozone (O₃) on respiratory mortality, while only a few studies compared the association between different O₃ indicators and health.

Methods

This study explores the relationship between daily respiratory hospitalization and multiple ozone indicators in Guangzhou, China, from 2014 to 2018. It uses a time-stratified case-crossover design. Sensitivities of different age and gender groups were analyzed for the whole year, the warm and the cold periods. We compared the results from the single-day lag model and the moving average lag model.

Results

The results showed that the maximum daily 8 h average ozone concentration (MDA8 O₃) had a significant effect on the daily respiratory hospitalization. This effect was stronger than for the maximum daily 1 h average ozone concentration (MDA1 O₃). The results further showed that O₃ was positively associated with daily respiratory hospitalization in the warm season, while there was a significantly negative association in the cold season. Specifically, in the warm season, O₃ has the most significant effect at lag 4 day, with the odds ratio (OR) equal to 1.0096 [95% confidence intervals (CI): 1.0032, 1.0161]. Moreover, at the lag 5 day, the effect of O₃ on the 15-60 age group was less than that on people older than 60 years, with the OR value of 1.0135 (95% CI: 1.0041, 1.0231) for the 60+ age group; women were more sensitive than men to O₃ exposure, with an OR value equal to 1.0094 (95% CI: 0.9992, 1.0196) for the female group.

Conclusion

These results show that different O₃ indicators measure different impacts on respiratory hospitalization admission. Their comparative analysis provided a more comprehensive insight into exploring associations between O₃ exposure and respiratory health.

Associations between Different Ozone Indicators and Cardiovascular Hospital Admission: A Time-Stratified Case-Crossover Analysis in Guangzhou, China

Epidemiological studies reported that ozone (O₃) is associated with cardiovascular diseases. However, only few of these studies examined the impact of multiple O₃ indicators on cardiovascular hospital admissions. This study aimed to explore and compare the impacts of different O₃ indicators on cardiovascular hospital admissions in Guangzhou, China. Based upon the data on daily cardiovascular hospital admissions, air pollution, and meteorological factors in Guangzhou from 2014 to 2018, a time-stratified case-crossover design model was used to analyze the associations between different O₃ indicators and cardiovascular hospital admissions. Moreover, the sensitivities of different age and gender groups were analyzed for the whole year and different seasons (i.e., warm and cold). During the warm season, for the single-pollutant model, the odds ratio (OR) value of cardiovascular hospital admissions was 1.0067 (95% confidence interval (CI): 1.0037, 1.0098) for every IQR increase in MDA8 O₃ at a lag of five days. The effect of O₃ on people over 60 year was stronger than that on the 15-60 years age group. Females were more sensitive than males to O₃ exposure. These results provided valuable references for further scientific research and environmental improvement in Guangzhou. Given that short-term O₃ exposure poses a threat to human health, the government should therefore pay attention to prevention and control policies to reduce and eliminate O₃ pollution and protect human health.

Overview of the Mechanisms of Oxidative Stress: Impact in Inflammation of the Airway Diseases

Inflammation of the human lung is mediated in response to different stimuli (e.g., physical, radioactive, infective, pro-allergenic or toxic) such as cigarette smoke and environmental pollutants. They often promote an increase in inflammatory activities in the airways that manifest themselves as chronic diseases (e.g., allergic airway diseases, asthma, chronic bronchitis/chronic obstructive pulmonary disease (COPD) or even lung cancer). Increased levels of oxidative stress (OS) reduce the antioxidant defenses, affect the autophagy/mitophagy processes, and the regulatory mechanisms of cell survival, promoting inflammation in the lung. In fact, OS potentiate the inflammatory activities in the lung, favoring the progression of chronic airway diseases. OS increases the production of reactive oxygen species (ROS), including superoxide anions (O₂^-), hydroxyl radicals (OH) and hydrogen peroxide (H₂O₂), by the transformation of oxygen through enzymatic and non-enzymatic reactions. In this manner, OS reduces endogenous antioxidant defenses in both nucleated and non-nucleated cells. The production of ROS in the lung can derive from both exogenous insults (cigarette smoke or environmental pollution) and endogenous sources such as cell injury and/or activated inflammatory and structural cells. In this review, we describe the most relevant knowledge concerning the functional interrelation between the mechanisms of OS and inflammation in airway diseases.

Nonlinear effect of air pollution on adult pneumonia hospital visits in the coastal city of Qingdao, China: A time-series analysis

Many studies have illustrated adverse effects of short-term exposure to air pollution on human health, which usually assumes a linear exposure-response (E-R) function in the delineation of health effects due to air pollution. However, nonlinearity may exist in the association between air pollutant concentrations and health outcomes such as adult pneumonia hospital visits, and there is a research gap in understanding the nonlinearity. Here, we utilized both the distributed lag model (DLM) and nonlinear model (DLNM) to compare the linear and nonlinear impacts of air pollution on adult pneumonia hospital visits in the coastal city of Qingdao, China. While both models show adverse effects of air pollutants on adult pneumonia hospital visits, the DLNM shows an attenuation of E-R curves at high concentrations. Moreover, the DLNM may reveal delayed health effects that may be missed in the DLM, e.g., ozone exposure and pneumonia hospital visits. With the stratified analysis of air pollutants on adult pneumonia hospital visits, both models consistently reveal that the influence of air pollutants is higher during the cold season than during the warm season. Nevertheless, they may behave differently in terms of other subgroups, such as age, gender and visit types. For instance, while no significant impact due to PM_2.5 in any of the subgroups abovementioned emerges based on DLM, the results from DLNM indicate statistically significant impacts for the subgroups of elderly, female and emergency department (ED) visits. With respect to adjustment by two-pollutants, PM₁₀ effect estimates for pneumonia hospital visits were the most robust in both DLM and DLNM, followed by NO₂ and SO₂ based on the DLNM. Considering the estimated health effects of air pollution relying on the assumed E-R functions, our results demonstrate that the traditional linear association assumptions may overlook some potential health risks.

Relationship between exposure to ozone and exacerbation requiring hospital admission among patients with asthma: a case-control study in central Taiwan

OBJECTIVE

The convergence of asthma and air pollutants in ageing populations is currently a growing health issue worldwide, and hence there is an essential need to investigate the association between exposure to air pollution, particularly ozone (O₃), and exacerbation requiring admission in patients with asthma.

SETTING

A case-control study at a tertiary referral hospital in central Taiwan.

PARTICIPANTS

We used an asthma cohort, which included 11 400 patients with asthma, for the period 2006-2018 at Taichung Veterans General Hospital.

PRIMARY AND SECONDARY OUTCOME MEASURES

We identified patients who had admitted for exacerbation as cases and selected patients with asthma without exacerbation, matching (1:4) the cases for age, gender and season of exacerbation, as controls. Data on hourly level of air pollutants were obtained from the Taiwan Environmental Protection Administration. We used conditional logistic regression and calculated adjusted ORs (adjORs) with 95% CIs.

RESULTS

We enrolled 11 400 participants with asthma, and 4.4% (501) of them had been admitted for exacerbation. Participants with asthma with exacerbation requiring hospitalisation were exposed to a higher level of O₃ 8-hour daily maximum (adjOR 1.009, 95% CI 1.001 to 1.016) and were more likely to have high Charlson Comorbidity Index (CCI ≥3; adjOR 2.198, 95% CI 1.729 to 2.794) and asthma-chronic obstructive pulmonary disease overlap (adjOR 4.542, 95% CI 3.376 to 6.611) compared with those without exacerbation. The aforementioned associations between exacerbation of asthma requiring hospitalisation and exposure to O₃ were similar when defined by either O₃ 1-hour daily maximum or O₃ 24-hour average. Moreover, the O₃ relevant exacerbation of asthma mainly existed in those aged older than 65 years and patients with medical comorbidities, including gastrointestinal diseases, cardiovascular diseases, neurological diseases, diabetes and renal disease.

CONCLUSIONS

Our findings highlight the need for vigilance of exposure to O₃ among elderly with asthma, particularly those with medical comorbidities. Further studies are warranted to investigate the underlying mechanisms.

Effects of Air Pollutants on Airway Diseases

Air pollutants include toxic particles and gases emitted in large quantities from many different combustible materials. They also include particulate matter (PM) and ozone, and biological contaminants, such as viruses and bacteria, which can penetrate the human airway and reach the bloodstream, triggering airway inflammation, dysfunction, and fibrosis. Pollutants that accumulate in the lungs exacerbate symptoms of respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Asthma, a heterogeneous disease with complex pathological mechanisms, is characterized by particular symptoms such as shortness of breath, a tight chest, coughing, and wheezing. Patients with COPD often experience exacerbations and worsening of symptoms, which may result in hospitalization and disease progression. PM varies in terms of composition, and can include solid and liquid particles of various sizes. PM concentrations are higher in urban areas. Ozone is one of the most toxic photochemical air pollutants. In general, air pollution decreases quality of life and life expectancy. It exacerbates acute and chronic respiratory symptoms in patients with chronic airway diseases, and increases the morbidity and risk of hospitalization associated with respiratory diseases. However, the mechanisms underlying these effects remain unclear. Therefore, we reviewed the impact of air pollutants on airway diseases such as asthma and COPD, focusing on their underlying mechanisms.

Prospects for ozone pollution control in China: An epidemiological perspective

Severe surface ozone pollution has become widespread in China. To protect public health, Chinese scientific communities and government agencies have striven to mitigate ozone pollution. However, makers of pollution mitigation policies rarely consider epidemiological research, and communication between epidemiological researchers and the government is poor. Therefore, this article reviews the current mitigation policies and the National Ambient Air Quality Standard (NAAQS) for ozone from an epidemiological perspective and proposes recommendations for researchers and policy makers on the basis of epidemiological evidence. We review current nationwide ozone control measures for mitigating ozone pollution from four dimensions: the integration of ozone and particulate matter control, ozone precursors control, ozone control in different seasons, and regional cooperation on the prevention of ozone pollution. In addition, we present environmental and epidemiological evidence and propose recommendations and discuss relevant ozone metrics and the criteria values of the NAAQS. We finally conclude that the disease burden attributable to ozone exposure in China may be underestimated and that the epidemiological research regarding the health effects of integrating ozone and particulate matter control is insufficient. Furthermore, atmospheric volatile organic compounds are severely detrimental to health, and related control policies are urgently required in China. We recommend a greater focus on winter ozone pollution and conclude that the health benefits of regional cooperation on ozone control and prevention are salient. We argue that daily average ozone concentration may be a more biologically relevant ozone metric than those currently used by the NAAQS, and accumulating epidemiological evidence supports revision of the standards. This review provides new insight for ozone mitigation policies and related epidemiological studies in China.

Mortality and morbidity of asthma and chronic obstructive pulmonary disease associated with ambient environment in metropolitans in Taiwan

Background

This study investigated risks of mortality from and morbidity (emergency room visits (ERVs) and outpatient visits) of asthma and chronic obstructive pulmonary disease (COPD) associated with extreme temperatures, fine particulate matter (PM_2.5), and ozone (O₃) by sex, and age, from 2005 to 2016 in 6 metropolitan cities in Taiwan.

Methods

The distributed lag non-linear model was employed to assess age (0–18, 19–39, 40–64, and 65 years and above), sex-cause-specific deaths, ERVs, and outpatient visits associated with extreme high (99^th percentile) and low (5^th percentile) temperatures and PM_2.5 and O₃ concentrations at 90^th percentile. Random-effects meta-analysis was adopted to investigate cause-specific pooled relative risk (RR) and 95% confidence intervals (CI) for the whole studied areas.

Results

Only the mortality risk of COPD in the elderly men was significantly associated with the extreme low temperatures. Exposure to the 90^th percentile PM_2.5 was associated with outpatient visits for asthma in 0–18 years old boys [RR = 1.15 (95% CI: 1.09–1.22)]. Meanwhile, significant elevation of ERVs of asthma for females aged 40–64 years was associated with exposure to ozone, with the highest RR of 1.21 (95% CI: 1.05–1.39).

Conclusions

This study identified vulnerable subpopulations who were at risk to extreme events associated with ambient environments deserving further evaluation for adaptation.

Short-term effects of ambient temperature and pollutants on the mortality of respiratory diseases: A time-series analysis in Hefei, China

BACKGROUND

The air pollution has become an important environmental health problem due to its adverse health effect. The objective of this study was to investigate the effects of ambient temperature and pollutants on mortality of respiratory diseases (RD) in Hefei, China, a typical inland city.

METHODS

Nonlinear exposure-response dependencies and delayed effects of urban daily mean temperature (DMT) and pollutants were evaluated by distributed lag non-linear models (DLNM). To further explore this effect, different genders and ages were also examined by stratified analysis.

RESULTS

A total of 12876 deaths from RD were collected from January 1, 2014 to December 31, 2018 in Hefei, China. There was a U-shaped correlation between DMT and RD mortality, and the RD mortality rised by 11.6% (95% CI: 2.2-22.0%) when the DMT was 35.8 °C (reference temperature is 20 °C). The results show that risk of death with short-term exposure to elevated concentrations of PM₁₀ and SO₂ was not significant. The maximum hysteresis and cumulative relative risk (RR) of RD mortality were 1.012 (95% CI: 1.003 ~ 1.021, lag 0 day) and 1.072 (95% CI: 1.014 ~1.133, lag 10 days) for each 10 μg/m³ augment in NO₂; 1.005 (95% CI: 1.001-1.009, lag 0 day) and 1.027 (95% CI: 1.004-1.051, lag 10 days) for each 10 μg/m³ augment in O_3; a negative association between CO exposure and the cumulative risk of death was observed (RR = 0.964, 95% CI: 0.935-0.993, lag 07 days). Subgroup analysis showed the effect of high temperatures, NO_2, O₃ and CO exposure was still statistically significant for the elderly and male.

CONCLUSION

The present study found that short-term exposure to high temperature, NO_2, O₃ and CO were significantly associated with the risk of RD mortality and male as well as elderly are more susceptible to these factors.

[Research on the correlation between otorhinolaryngologic diseases and environmental meteorological factors in children]

Objective:To explore the correlation between acute otitis media（AOM）, acute pharyngitis（AP） and allergic rhinitis（AR） and environmental-meteorological factors in children in Lanzhou. Method:Data were collected in 2015-2017 from the outpatient department and emergency department of Otolaryngology of one hospital in Lanzhou. The association between clinical data and the environmental meteorological factors during the same period, including the air quality index（AQI）, PM2.5, PM10, CO, NO₂, SO₂, O3, average temperature, average air pressure, average wind speed, average humidity in Lanzhou, was analyzed. Result:The incidence of AOM was positively correlated with AQI, PM2.5, PM10, CO, NO₂, SO₂, average air pressure, and was negatively correlated with O3, average wind speed and average air temperature, but not correlated with average humidity. The incidence of AP was positively correlated with average temperature and average humidity, and not correlated with other 9 factors. The incidence of AR was correlated with all 10 environmental meteorological factors except for O3.The number of children with AOM, AP and AR varied with different seasons. Environmental meteorological factors have single lag and cumulative lag effects on the incidence of children with AOM, AP and AR, and difference between the single lag and cumulative lag time was observed. Conclusion:There may be some correlation between the environmental meteorological factors and the incidence of AOM, AP, AR in children, and there is a lag effect. The incidence of pediatric AOM, AP and AR is affected by seasonal factors.

Analysis of related factors and disease costs of respiratory infection and environmental pollution in children

BACKGROUND

In recent years, air pollution and the number of children with respiratory tract infections increased. This also increased the burden related to the treatment of disease, so the government and relevant departments need to strengthen their management.

OBJECTIVE

The aim of the present study was to quantitatively analyze the relationship between respiratory infection and air quality in children and gain insight into the burden of related diseases.

METHODS

Data regarding outpatient and emergency department visits in children of 14 years or younger in 16 public and private medical institutions were collected for four months. Routine air quality monitoring data in Shanghai from the same period were correlated with these medical data by descriptive statistics, Pearson's correlation analysis and multivariate linear regression analysis.

RESULTS

There was a positive correlation between respiratory tract infections in 73376 children and Air Quality Index (AQI), PM2.5, SO2 and NO2 levels. The total medical expense per patient was 80.22 yuan, and the average compensation ratio of medical insurance per patient was 18.95%. The increase in AQI and the concentration of major air pollutants will lead to increased medical treatment for children with respiratory diseases.

CONCLUSION

It is suggested that the intensity of air pollution control should be increased, so that the special period of childhood respiratory protection is strengthened. Moreover, child medical insurance coverage should also be moderately increased to safeguard the rights and interests of children's health.

Short-term effect of relatively low level air pollution on outpatient visit in Shennongjia, China

BACKGROUND

Many cities in China are currently experiencing severe air pollution due to modernization. Previous studies investigating the effects of air pollutants exposure were particularly conducted in severe air polluted area and studies in low pollution areas were sparse.

METHODS

To quantitatively assess the short-term effects of ambient air pollutants (PM_2.5, PM₁₀, SO₂, NO₂, CO and O₃) on outpatient visits in low pollution area, we conducted a time-series analysis from Jan 1, 2015 to Dec 31, 2016 in Shennongjia, China. Generalized additive model (GAM) was used to evaluate the influence of PM_2.5 on daily hospital outpatient visits with different lag structures. We also conducted stratified analysis to explore the association between PM_2.5 concentration and outpatient visits in different seasons.

RESULTS

In the present study, per IQR increment of PM_2.5, PM₁₀, NO₂, CO and O₃ were related with 1.92% (0.76%-3.09%), 1.92% (0.77%-3.07%), 2.74% (95% CI: 1.65%-3.83%), 1.89% (95% CI: 0.68%-3.10%) and 2.30% (95% CI: 0.65%-3.95%) increase on respiratory outpatient visits. Significant associations were found between PM_2.5, PM₁₀, NO₂ and respiratory outpatient visits at lag0:1, lag0:2 days. The effects of PM_2.5 were more evident in the cool season than in the warm season.

CONCLUSIONS

Our study showed that short-term exposures to PM_2.5, PM₁₀, NO₂, CO and O₃ were related with increased risk of outpatient visits of respiratory diseases, and highlighted the adverse effect of air pollutants exposure, especially PM_2.5 exposure in cool season on health in low pollution area.

The Association between Air Pollution and Outpatient and Inpatient Visits in Shenzhen, China

Nowadays, air pollution is a severe environmental problem in China. To investigate the effects of ambient air pollution on health, a time series analysis of daily outpatient and inpatient visits in 2015 were conducted in Shenzhen (China). Generalized additive model was employed to analyze associations between six air pollutants (namely SO₂, CO, NO₂, O₃, PM₁₀, and PM_2.5) and daily outpatient and inpatient visits after adjusting confounding meteorological factors, time and day of the week effects. Significant associations between air pollutants and two types of hospital visits were observed. The estimated increase in overall outpatient visits associated with each 10 µg/m³ increase in air pollutant concentration ranged from 0.48% (O₃ at lag 2) to 11.48% (SO₂ with 2-day moving average); for overall inpatient visits ranged from 0.73% (O₃ at lag 7) to 17.13% (SO₂ with 8-day moving average). Our results also suggested a heterogeneity of the health effects across different outcomes and in different populations. The findings in present study indicate that even in Shenzhen, a less polluted area in China, significant associations exist between air pollution and daily number of overall outpatient and inpatient visits.

Major air pollutants and risk of COPD exacerbations: a systematic review and meta-analysis

Background

Short-term exposure to major air pollutants (O₃, CO, NO₂, SO₂, PM₁₀, and PM_2.5) has been associated with respiratory risk. However, evidence on the risk of chronic obstructive pulmonary disease (COPD) exacerbations is still limited. The present study aimed at evaluating the associations between short-term exposure to major air pollutants and the risk of COPD exacerbations.

Methods

After a systematic search up until March 30, 2016, in both English and Chinese electronic databases such as PubMed, EMBASE, and CNKI, the pooled relative risks and 95% confidence intervals were estimated by using the random-effects model. In addition, the population-attributable fractions (PAFs) were also calculated, and a subgroup analysis was conducted. Heterogeneity was assessed by I².

Results

In total, 59 studies were included. In the single-pollutant model, the risks of COPD were calculated by each 10 μg/m³ increase in pollutant concentrations, with the exception of CO (100 μg/m³). There was a significant association between short-term exposure and COPD exacerbation risk for all the gaseous and particulate pollutants. The associations were strongest at lag0 and lag3 for gaseous and particulate air pollutants, respectively. The subgroup analysis not only further confirmed the overall adverse effects but also reduced the heterogeneities obviously. When 100% exposure was assumed, PAFs ranged from 0.60% to 4.31%, depending on the pollutants. The adverse health effects of SO₂ and NO₂ exposure were more significant in low-/middle-income countries than in high-income countries: SO₂, relative risk: 1.012 (95% confidence interval: 1.001, 1.023); and NO₂, relative risk: 1.019 (95% confidence interval: 1.014, 1.024).

Conclusion

Short-term exposure to air pollutants increases the burden of risk of COPD acute exacerbations significantly. Controlling ambient air pollution would provide benefits to COPD patients.

The Effects of Air Pollution on Ischemic Stroke Admission Rate

The present study aimed to determine the relationship between the level of air pollutants and the rate of ischemic stroke (IS) admissions to hospitals. In this retrospective cross-sectional study, stroke admissions (January-March 2012 and 2013) to an emergency department and air pollution and meteorological data were gathered. The relationship between air pollutant levels and hospital admission rates were evaluated using the generalize additive model. In all 379 patients with IS were referred to the hospital (52.5% male; mean age 68.2±13.3 years). Both transient (p<0.001) and long-term (p<0.001) rises in CO level increases the risk of IS. Increased weekly (p<0.001) and monthly (p<0.001) average O₃ levels amplifies this risk, while a transient increase in NO₂ (p<0.001) and SO₂ (p<0.001) levels has the same effect. Long-term changes in PM₁₀ (p<0.001) and PM_2.5 (p<0.001) also increase the risk of IS. The findings showed that the level of air pollutants directly correlates with the number of stroke admissions to the emergency department.

Temperature effects on outpatient visits of respiratory diseases, asthma, and chronic airway obstruction in Taiwan

This study evaluated the risk of outpatient visits for respiratory diseases, asthma, and chronic airway obstruction not elsewhere classified (CAO) associated with ambient temperatures and extreme temperature events from 2000 to 2008 in Taiwan. Based on geographical and socioeconomics characteristics, this study divided the whole island into seven areas. A distributed lag non-linear model was used to estimate the area-disease-specific cumulative relative risk (RR), and random-effect meta-analysis was used to estimate the pooled RR of outpatient visits, from lag 0 to lag 7 days, associated with daily temperature, and added effects of prolonged extreme heat and cold for population of all ages, the elderly and younger than 65 years. Pooled analyses showed that younger population had higher outpatient visits for exposing to low temperature of 18 °C, with cumulative 8-day RRs of 1.36 (95% confidence interval (CI) 1.31-1.42) for respiratory diseases, 1.10 (95% CI 1.03-1.18) for asthma, and 1.12 (95% CI 1.02-1.22) for CAO. The elderly was more vulnerable to high temperature of 30 °C with the cumulative 8-day RR of 1.08 (95% CI 1.03-1.13) for CAO. Elevated outpatient visits for all respiratory diseases and asthma were associated with extreme heat lasting for 6 to 8 days. On the contrary, the extreme cold lasting more than 8 days had significant negative association with outpatient visits of all respiratory diseases. In summary, elderly patients of respiratory diseases and CAO are vulnerable to high temperature. Cold temperature is associated with all types of respiratory diseases for younger patients.

The Effects of Air Pollution on Cardiovascular and Respiratory Causes of Emergency Admission

INTRODUCTION

Today, air pollution is one of the critical problems in metropolitans and necessary preparations are needed for confronting this crisis. The present study was based on the goal of determining the relationship of air pollutant levels with the rate of emergency admissions for respiratory and cardiovascular patients.

METHODS

In the present retrospective cross-sectional study, all respiratory and cardiovascular patients, referred to emergency department during 2012, were assessed. The meteorological and air pollution data were collected. Information regarding the numbers and dates (month, day) of admission for respiratory and cardiovascular diseases was achieved from the hospital's electronic registration system. The relation of air pollution and respiratory and cardiovascular admissions were analyzed by generalize additive model (GAM).

RESULTS

5922 patients were assessed which included 4048 (68.36%) cardiovascular and 1874 (31.64%) respiratory. Carbon monoxide (CO) level was an independent risk factor of cardiovascular disease on the same day (RR=1.49; 95% CI: 1.25- 1.77; P<0.001), the day before (RR=1.22; 95% CI: 1.02- 1.45; P=0.03), and the last two days (RR=1.3; 95% CI: 1.09- 1.54; P<0.001). The same process was repeated for ozone (O3). In addition, the O3 level on the same day (RR=1.49; 95% CI: 1.25- 1.77; P<0.001), the day before (RR=1.22; 95% CI: 1.02- 1.45; P=0.03), the last two days (RR=1.3; 95% CI: 1.09- 1.54; P<0.001), and the last week (RR=1.004; 95% CI: 1.0007-1.008; P=0.02) were independent risk factors of respiratory admissions. The increased level of particulate matter less than 2.5 micrometers in diameter (PM2.5) like O3 led to growth in the admissions to emergency department.

CONCLUSION

The findings of the present study suggested that rising levels of CO and O3 during two days leads to a significant increase in cardiovascular admission on the third day. Furthermore, increase in O3, PM2.5, nitrogen dioxide (NO2), and CO levels causes a rise in respiratory admissions to emergency department.