Acute effects of black carbon and PM2.5 on children asthma admissions: A time-series study in a Chinese city
Introduction
Short term exposure to ambient air pollution has been linked to adverse health effects, including increased mortality, increased rates of hospital admission and emergency department visit, exacerbated chronic respiratory condition, and decreased lung function (Brunekreef and Holgate, 2002, Dockery et al., 2005, Goldberg et al., 2011, Wang et al., 2013). Among various pollutants in the ambient mixture, fine particle (PM2.5, defined as particle less than 2.5 mm in aerodynamic diameter) shows the most consistent association with adverse health effects (Pope and Dockery, 2006). A number of epidemiologic studies have shown that urban particulate matter (PM) is associated with pulmonary inflammation and increased respiratory symptoms, deterioration of lung function, increased hospital admissions, and mortality from inflammatory lung injury (Pope and Dockery, 2006, Smith et al., 2009, Steerenberg et al., 2001, Suglia et al., 2008). Black carbon (BC) is an important component of PM, which is a traffic-related particle produced as a combustion by-product. It has been associated more strongly than PM2.5 with the adverse health effects. (Gold et al., 2005, O'Neill et al., 2005, Schwartz et al., 2005).
In vitro and in vivo studies have shown that BC stimulates reactive oxygen species production and cytokine-mediated inflammation (Alessandrini et al., 2009, Soto et al., 2008), which may play a major role in adverse health effects related to the exacerbation of cardiopulmonary disease (Pope and Dockery, 2006). Epidemiologic studies using BC as an indicator of traffic-related air pollution suggest that it can increase the risk of acute respiratory inflammation in elderly subjects with asthma (Jansen et al., 2005), decrease lung function (Suglia et al., 2008), and decrease antioxidant activity and induce systemic inflammation and platelet formation in subjects with coronary artery disease (Delfino et al., 2008). Exposure to black carbon was associated with increased nitric oxide in exhaled breath, a marker of airway inflammation (Mar et al., 2005). Fischer et al. (2002) and Steerenberg et al. (2001) reported increases in airway inflammatory markers in schoolchildren exposed to black smoke (BS), and Delfino et al. (2006) reported a robust association between elemental carbon (EC) and airway inflammation in asthmatic children.
Levels of PM2.5 and BC in China are among the highest in the world. The relationship between PM2.5 and adverse health outcome has been examined in several large Chinese cities, including Shanghai (Kan et al., 2007), Chongqing (Venners et al., 2003), Shenyang (Ma et al., 2011) and Guangzhou(Yang et al., 2012). These single-city analyses basically followed the commonly used time-series (Kan et al., 2007, Ma et al., 2011, Venners et al., 2003) and case-crossover (Yang et al., 2012) approaches, and their results were in accordance with those reported from developed countries. PM2.5 has been considered as a criteria pollutant in China since the year of 2012. However, few studies have examined the adverse health effect of BC in China duo to the lacking of monitoring data. To our knowledge, only three studies in China have found the associations of black carbon with acute respiratory inflammation in school-aged children in Beijing (Lin et al., 2011), and with total and cardiovascular mortality (Geng et al., 2013) and hospital visits (Wang et al., 2013) in Shanghai. In the current study, we aimed to conduct a time-series study in China to evaluate the associations of black carbon and PM2.5 with daily asthma admission in Shanghai, the largest city in China.
Section snippets
Data
Our study area involved nine urban districts of Shanghai, covering an area of 279 km2. There are about seven million permanent residents within the area. We obtained daily asthma hospital admission data from Shanghai Children's Medical Center. Since 2006, all hospital authority outpatient and inpatient data, including demographic characteristics (sex, age, and family social-economic status), dates of admission and discharge, and diagnoses using the International Classification of Diseases,
Results
Of 114,673 child asthma admissions from 1 January 2007 to 31 of July 2012 (2040 days), 77,135 (67.3%) were boys and 37,538 (32.7%) were girls. The percentages of total asthma admissions by age group were 65.6% (75274 children) for 0–4 years old and 34.4% (39399 children) for 5–14 years old. The mean daily concentrations of black carbon and PM2.5 were 3.49 μg/m3 and 40.88 μg/m3, respectively. Table 1 showed the summary statistics of asthma admissions, BC and PM2.5 concentrations, and weather
Discussion
Compared with the US National Ambient Air Quality Standards (15 μg/m3 for annual mean and 35 μg/m3 for 24-h mean) (U.S. EPA, 2006), and the Global Air Quality Guidelines (10 μg/m3 for annual mean and 25 μg/m3 for 24-h mean) (World Health Organization, 2006), the PM2.5 levels in Shanghai were higher than the reported levels in western countries. Evidence from this study showed that the current level of PM2.5 and black carbon in Shanghai are associated with children's asthma attacks when adjusting
Conflict of interest
All authors declare that they have no competing interests.
Acknowledgment
The study was supported the Gong-Yi Program of China Meteorological Administration (grant no. GYHY201206027), by the Science and Technology Commission of Shanghai Municipality (grant no. 12DZ1202600), the Health and Family Planning commission of Pudong District, Shanghai (grant no. PW2013D-9), the Health and Family Planning commission of Shanghai (grant nos. 2013HP045 an 20114010), and the Shanghai Key Laboratory of Meteorology and Health (grant no. QXJK201302). The authors declare they have no
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These authors contributed equally to this work.