Air pollution and hospital admissions for respiratory diseases in Lanzhou, China
Introduction
A number of epidemiological studies have observed associations between air pollutants, including particulates, SO2, CO, NO2 and O3, and negative health effects, such as higher mortality levels, greater hospital admissions and increased outpatient visits (Dockery et al., 1994, Kan et al., 2007, Lee et al., 2000, Schwartz, 1999, Yang et al., 2004, Zeka et al., 2005).
The relationship between hospital admissions for respiratory diseases and air pollution has been assessed in the developed countries of Europe and in the United States (Atkinson et al., 2001, Medina-Ramón et al., 2006, Schwartz, 1994, Schwartz, 1996, Wilson et al., 2005, Zanobetti et al., 2000). For example, the study evaluated the effect of PM10 on respiratory hospital admissions in 36 US cities, finding that a 10 μg/m3 increase in PM10 during the warm season resulted in a 1.47% increase in chronic obstructive pulmonary disease admissions and a 0.84% increase in pneumonia admissions (Medina-Ramón et al., 2006). The APHEA 2 project investigated the short-term health effects of particulates in eight European cities. When PM10 increased by 10 μg/m3, admissions for chronic obstructive pulmonary disease plus asthma and total respiratory diseases in patients ≥65 yrs increased by 1.0% and 0.9%, respectively (Atkinson et al., 2001). Positive associations between air pollutants and respiratory disease hospital admissions have also been reported in Asia (Chang et al., 2003, Wong et al., 1999, Xu et al., 1995, Zhou et al., 1997). For example, in Hong Kong, NO2, SO2 and PM10 increases of 10 μg/m3 were associated with total respiratory disease hospitalization increased by 2.0%, 1.3% and 1.6%, respectively, and chronic obstructive pulmonary disease increased by 2.9%, 2.3% and 1.9%, respectively (Wong et al., 1999).
Lanzhou (102°35′55″–104°34′29″E, 35°34′20″–37°07′N) is located in the semi-arid region of northwest China, situated in a typical valley basin with low rainfall, high evaporation, low wind speeds, high calm wind frequency and a thick inversion layer (An et al., 2006). Lanzhou is also an industrial city with significant petrochemical, metallurgical and mechanical sectors. These factors combine to make Lanzhou one of the most seriously air-polluted cities in China and the world as a whole, and top PM10-contaminated city in China (WHO, 2011). The objective of our time-series analysis was to assess the acute effects of air pollutants on total respiratory diseases hospital admissions, upper respiratory tract infection, pneumonia and chronic obstructive pulmonary disease in Lanzhou, by using day-to-day air pollutants concentrations after controlling long-term trends and confounding effects of weather. We performed the study on the daily hospital admissions of 4 major hospitals and the air pollutant concentrations from 3 air quality monitoring stations from 2001 to 2005. The total of respiratory hospital admissions were 28,057.
Section snippets
Hospital admissions
We obtained admission records for respiratory diseases (from 1 January 2001 to 31 December 2005) from 4 general hospitals, representing the majority of hospital admissions in Lanzhou. These records contain the date of admission, age, gender, and discharge diagnosis from the tenth revision of the international classification of diseases (ICD-10, Ministry of Health Statistical Information Center, 2001) for each patient. The following disease categories were analyzed separately: total respiratory
Results
No air pollutant's daily mean, with the exception of PM10, exceeded that of China's national air quality secondary standards (PM10:150 μg/m3, SO2: 150 μg/m3, NO2: 80 μg/m3) (Table 1). The PM10 and SO2 concentrations both exceeded the 24-h means of the WHO air quality guidelines (PM10 IT-1: 70 μg/m3, SO2: 20 μg/m3), and the NO2 concentrations exceeded the annual mean of the WHO guidelines (NO2: 40 μg/m3).
A certain degree of positive correlation did exist among the pollutants, especially between
Discussion
Since the 1990s, time series analysis based on the generalized additive model (GAM) has been widely used to study the health effects of acute exposure to air pollution. Close relationships have been confirmed between air pollution and mortality rates, the number of outpatient visits and the amount of hospital admissions for heart and lung disease. Previous studies have obtained similar results despite being conducted in different locations with different atmospheric pollution backgrounds
Conclusions
Associations between air pollutants and respiratory hospitalizations do exist with a lag effect in Lanzhou, which is one of the most seriously air-polluted cities in the world. The lag was 3–5 days for PM10, 1–3 days for SO2 and 1–4 days for NO2, and the aged and female patients are shown to be more vulnerable to air pollutants.
Acknowledgments
This study was supported by the National Natural Science Foundation of China (41075102; 41005087), the Fundamental Research Funds for the Central Universities (lzujbky-2013-m03; lzujbky-2012-135) and the Public Welfare Project of the China Meteorological Administration (GYHY201106034).
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