1. Introduction
Air pollution has a serious impact on human health, in particular the incidence of lung cancer, which is the most common cancer in the world. In 2013, the World Health Organization (WHO) classified outdoor air pollution as carcinogenic to humans (International Agency for Research on Cancer, Group 1) [
1]. Residents exposed to air pollution have shown higher frequencies of mutations in cells, DNA damage and other chromosomal aberrations which lead to increasing the incidence of lung cancer and polycyclic aromatic hydrocarbons (PAHs) is the most important pathogenic factor causing these lesions [
2,
3]. Exposure to PM
10, SO
2, and NO
2 significantly increase the risk of lung cancer [
4]. As a developing country, China has the world’s most serious burden of lung cancer[
5], incidence rate of lung cancer was 50.9 per 100,000 for men and 22.4 per 100,000 for women in 2015 [
6]. Therefore, knowing which pollutant among air pollution factors is most closely related to lung cancer is of great significance.
Scholars have studied the relationship between components of air pollution and lung cancer in many regions of the world. For example, Raaschou-Nielsen et al. [
7] found that between 1985 and 2005, sulfur and nickel pollutants had the most significant effect on lung cancer in Europe. Furthermore, Li et al. [
8] found that in Hong Kong, automobile exhaust and trace metals accounted for most of the PM
10 pollution, and caused lung cancer. Finally, Guo et al. [
9] determined that in China, PM
2.5 and O
3 both had a significant statistic relation with the incidence of lung cancer.
Many studies have explored the potential health risks of PM
10 among residents in China. An et al. [
10] found that in 2009, most of China’s residents were exposed to air with an average annual PM
10 concentration of 40–100 μg/m
3. However, the PM
10 concentration safe limit suggested by WHO is 20 μg/m
3. Shen et al. [
11] found that the majority of the population in Henan Province, China were exposed to toxic air while Zhang et al. [
12] determined that in Beijing, with more city buildings and denser roads, the health risk to local residents increased as the concentration of PM
10 increased.
In recent years, rapid economic development has resulted in deleterious health impacts for the residents of many Asian countries. Many of these health impacts have been attributed to elevated concentrations of PM
10, and hence, there have been several studies focusing on PM
10 induced mortality rates. Chen et al. [
13] found that as the PM
10 concentration in northern China increased by 10 mg/m
3, lung cancer mortality increased by 3.4% to 13.6%. Furthermore, Chen et al. [
14] found that between 2010 and 2014, increased concentrations of PM
10 in Chengdu have resulted in increased mortality. Maleki et al. [
15] found that between2009 and 2014, high concentrations of PM
10 caused 3777 deaths in Ahvaz, Iran. Ho et al. [
16] determined that during 2012, high concentrations of PM
10 in Ho Chi Minh City, Vietnam killed 204 residents. Other scholars have focused on the negative effects of increased PM
10 concentrations on the economy. Hou et al. [
17] determined that in 2009, China’s health related economic losses due to PM
10 reached
$U.S. 106.5 billion, approximately equal to 2.1% of China’s Gross Domestic Product (GDP) in that year. Hou et al. [
18] also found that from 2008 to 2012, the average annual economic loss associated with PM
10 pollution was
$U.S. 9.5 billion.
Developed nations such as the Unites States and those in Europe have already experienced the industrialization process and suffered from the subsequent severe air pollution brought about by this. Consequently, these regions fully recognize the importance of improving air quality and have adopted various measures to reduce pollutant emissions in order to improve the health of the population. As a result of this process, new industries have developed which have helped to boost economic growth. Keuken et al. [
19] found that in Rotterdam, The Netherlands, by applying stringent emission standards to prevent high emitters near residential areas, the concentration of PM
10 was reduced by 18 μg/m
3 during the past 24 years, and the average life expectancy of the residents increased by 13 months over the same period. Carugno et al. [
20] found that between 2003 and 2014, after implementing air quality control policies such as renewal of vehicle exhaust systems and engines, incentives to purchase hybrid and electric vehicles, the decrease in PM
10 concentrations in Lombardy, Italy resulted in a reduction in the number of deaths caused by PM
10; approximately 343 people died during the first 5 years of the study, the number was reduced to 253 between 2007 and 2010, and between 2011 and 2014, the death toll was reduced to 208. Research conducted by Castro et al. [
21] showed that by applying national regulations such as fuel requirements and maximum permitted pollution levels, the decrease of PM
10 concentrations had a positive effect on economic growth, in the Agglomeration of Lausanne-Morges, Switzerland, during 2005 to 2015; health related impacts of the reduction of PM
10 concentration were monetarized at approximately CHF 36 million annually.
Many scholars have conducted air pollution and lung cancer studies in China, but there are few studies related to the air pollution and population health in the middle reaches of the Yangtze River. The aim of this paper was to understand the relationship between the incidence of lung cancer and air pollution in Nanchang, China and explore the characteristics of lung cancer incidence in different population demographics such as residence, gender and smoking history. Nanchang, the capital city of Jiangxi Province, is one of the central cities of the middle reaches of the Yangtze River and the core city of Poyang Lake eco economic zone. Automobile exhaust, soil dust, coal combustion, building dust and metallurgical dust are the major sources of air pollution in Nanchang. The incidence rate of newly diagnosed lung cancer cases was 55.9 per 100,000 for men and 24.8 per 100,000 for women in 2013 [
22]. It is of great practical significance to study the association between air pollution and the incidence of lung cancer, to give scientific countermeasures and suggestions for the protection of public health.
4. Discussion
As far as we know, this study is one of the few to study the relation between air pollution and lung cancer in middle reaches of Yangtze River. By using the grey correlation analysis method and DEA, the relationship between the incidence of lung cancer and air pollution factors in Nanchang city was explored. The results obtained by the two different analysis methods were similar, which reinforces the reliability of the results.
Our study found that, by using grey correlation analysis, among five air pollution factors (annual mean concentration of SO2, NO2, PM10, haze days, and API/AQI), PM10 was the most closely related to the incidence of lung cancer in Nanchang. This result was reinforced by DEA, which showed that PM10 was the most critical air pollution factor for lung cancer.
One interesting finding shows that the DEA effectiveness between air pollution and urban patients was greater than the DEA effectiveness between air pollution and rural patients, which means that air pollution has more impact on urban dwellers as compared to rural dwellers. After related research of pollution sources in Nanchang, we found that automobile exhaust, soil dust, coal-burning dust, building dust and metallurgical dust are the major sources of PM
10 in Nanchang. The main sources of pollution in urban areas are automobile exhaust emissions and industrial pollution. For rural areas, the main sources of pollution are automobile exhaust emissions, industrial pollution and pollution brought by ore (marble and limestone) mining and building stones processing [
44]. Quarries, cement plants and building materials processing plants around Nanchang are some of the traditional industries that brought serious air pollution. In rural development, some out-of-date or heavy polluting industry that unable to meet environmental requirements were relocated from urban areas to rural areas in order to avoid been shut down. Some government officials welcomed these companies in order to raise GDP in their jurisdictions. Another fact that cannot be ignored was that many rural residents actually work in urban areas, they breathed the same air as the urban dwellers. All of these factors greatly increased the incidence rate of lung cancer in rural residents.
Another interesting finding is that the DEA effectiveness between air pollution and female patients was greater than the DEA effectiveness between air pollution and male patients, indicating that women are more susceptible to lung cancer caused by air pollution. For most adult Chinese women, they had to take on the responsibilities of a housewife including cooking. Unlike Western food, Chinese food uses a lot of oil in the cooking process. Hot pots and oil will produce a lot of cooking oil fumes which can potentially cause lung cancer. Several studies have shown that a significant association between cooking oil fumes and lung cancer exists for Chinese women [
45,
46]. Another reason is that due to the female physique is more sensitive to air pollution as compared to the male physique, women are more likely to suffer from passive smoking and cause lung cancer [
45,
47].
The DEA effectiveness between air pollution and smoking patients was greater than the DEA effectiveness between air pollution and non-smoking patients, meaning that smokers are more likely to cause lung cancer due to air pollution.
Industrialisation and urbanisation can promote economic development and increasing GDP growth rate. Between 2003 and 2014, Nanchang’s economy grew rapidly and GDP grew to more than five-fold within twelve years (from 64.1 billion Yuan in 2003, to 336.7 billion Yuan in 2014). However, the development of economy and the rapid growth of population have brought severe pressure to the atmosphere. As the capital city of Jiangxi Province, the problem of atmospheric pollution has become increasingly prominent in recent years. The main causes of air quality pollution are:
- (1)
Many enterprises have entered Nanchang, but the environmental management standards are not perfect, which makes many enterprises choose coal combustion equipment and out-of-date equipment, resulting in an increase in air pollutant emissions.
- (2)
The increase of population makes the real estate industry develop greatly in Nanchang, the construction of buildings blossom everywhere. Lack of dust control measures while demolishing old houses, removing wreckage and constructing new houses result in PM10 increased significantly. The boom in real estate industry also raises demand for more products from cement plants and quarries around Nanchang.
- (3)
Car ownership increased but lack of exhaust control measure. Motor vehicles with black smoke can be seen everywhere in the streets, and motor vehicle exhaust has become a major source of air pollution.
- (4)
The layout of industry zone is unreasonable and cannot match the meteorological condition. North industrial zone of Nanchang is located in the upper wind direction of the city's dominant wind direction, which is one of the direct reasons leading to the decline of air quality in the urban area.
According to our findings, we make the following recommendations:
- (1)
Priority should be given to low polluting industries to reduce the introduction of heavy polluting industries. Heavy polluting industries need to meet the environmental quality standards and pollutant discharge or emission standards before they can resume production. Increasing the usage of clean energy and renewable energy, reducing the usage of coal consumption, therefore the emission of air pollutants can greatly reduce.
- (2)
Strengthen the control of PM10 brought by real estate industry and related industries. Use water mist to reduce dust during demolition and muck trucks have to use dust cap. Encourage the use of environmentally friendly building materials. Trees and grass need to plant on open ground in order to reduce soil exposure. The pits left by quarries need more vegetation cover. By the end of 2016, the urban green coverage rate was 45%, and the greening rate of villages was 32%.
- (3)
The government should increase the proportion of new energy vehicles. More people should be encouraged to use public transport.
- (4)
Industrial areas need scientific planning to avoid areas that can affect the health of residents: an upper wind direction as the city’s dominant wind direction should be avoided, keeping a certain distance keep away from densely populated areas.