This study is focused on the linkage between lung cancer incidence rates and PM2.5 pollution. Researches conducted by leading research organizations in U.S. and Europe were reviewed and analyzed, and strong evidence exists that elevated fine particulate air pollution exposures are associated with significant increases in lung cancer mortality. The linkage between fine particulate air pollution and lung cancer motility is observed even after controlling for cigarette smoking, occupational exposure, and other risk factors. This finding is in alignment with observations in China which show an upward trend of lung cancer incidences coupled with a downward trend in the number of smokers. Currently, China lacks systematic research on the effect of PM2.5 on lung cancer. As a result, this paper investigated studies on the linkage between pollution and lung cancer incidence from decades of research conducted in the U.S. and Europe. One important step in solving this issue in China is through classifying PM2.5 pollution as a human cacinogen. Adequate government regulation, public awareness, regional collaboration and industrial compliance are also key to the successful control of PM2.5 pollution and smog.
Globally, lung cancer is estimated to account for almost 1.4 million cases of cancer each year and has been the most common cancer in the world for more than two decades [
Particulate matter pollutant is composed of a mixture of microscopic solids and liquid droplets suspended in air. These pollutants are made up of a number of components, including SOx, NOx, NH3, organic chemicals, volatile metals, soil or dust particles, and allergens (e.g. pollen or mold spores). When suspended in the atmosphere, PM2.5 particles are the major cause of reduced visibility in major Chinese cities, such as Beijing [
Unlike most air pollutants that consist of only one chemical compound, PM2.5 particles consist of a mixture of compounds and are formed from primary and secondary participles [
The environmental and health impact of PM2.5 is an emerging research topic in China. We have investigated lung cancer rate increase in Beijing area trying to find evidence of linkage between lung cancer and smog issue. We found that systematic research is needed in Beijing area. However, the linkage between lung cancer and fine particulate pollution has been investigated by many research organizations in the U.S. and Europe since the 1970s. For example, a famous study carried out by the American Cancer Society, in collaboration with U.S. universities, concluded that elevated fine particulate air pollution exposures were associated with significant increases in lung cancer mortality [
The objective of this study is to review the linkage between PM2.5 and lung cancer incidence using studies conducted by reputable research organizations in western countries. The goal is to show the Chinese community that while research into the relationship between lung cancer cases and PM2.5 pollution may be new in China, it has been investigated for decades by health organizations in western countries. These research findings can be used as the basis for further research in China and to inform the establishment of national policies for PM2.5 pollution control.
This study is a continuation of our previous research into smog issues in China [
The chemical composition of particulate matter changes with size [
Over the past decade, several studies have demonstrated the linkage between exposure to fine particulate matter and adverse health effects. One study, the 1995 American Cancer Society sponsored study, concluded that annual mortality rates due to cardiopulmonary disease and lung cancer increased alongside an increase in fine particulate matter concentrations [
The results of the 2002 follow-up study (2002 ACS study) showed significant linkage between PM2.5 pollutant levels and elevated risks for cardiopulmonary and lung cancer mortality. The study found that each 10 μg/m3 increase in the long-term average PM2.5 concentrations was associated with an approximately 4% increased risk of death from all natural causes, a 6% increased risk of death from cardiopulmonary disease, and an 8% increased risk of death from lung cancer. The 2002 ACS study concluded that long-term exposure to combustion related fine particulate air pollution is an important environmental risk factor for cardiopulmonary and lung cancer mortality. As shown in
Coal is still used as a major energy source in China, which emits SOx during combustion. Our previous research finding revealed that secondary PM2.5 particles contain significant amounts of SOx [
Furthermore, in the same 2002 study (Ref 2), researchers observed that the lung cancer risk associated with exposure to fine particulate matter was comparable to that from second-hand cigarette smoke. The result is in alignment with recent findings by researchers in China who observed that while the number of smokers has decreased, the lung cancer incidence rate has increased [
Beeson et al. found that there was an increased risk of lung cancer from smoking and occupational exposure if there was also long-term exposure to particulate pollution [
. Lung cancer incidence and mortality rates versus PM2.5 levels for 100 counties in North Carolina
PM2.5 Levels | |||
---|---|---|---|
7 μg/m3 | 12 μg/m3 | 17 μg/m3 | |
Lung Cancer Incidence Rate (per 100,000) | 66 | 72 | 80 |
Lung Cancer Mortality Rate (per 100,000) | 58 | 60 | 62 |
Note: Data cited from reference 13.
. Relative risk of lung cancer mortality associated with 10 μg/m3 change in PM2.5
Data Collection Period | |||
---|---|---|---|
1979-1983 | 1999-2000 | Average of two sets | |
Risk of Lung Cancer Mortality | 8% | 13% | 14% |
Note: Data cited from reference 16.
The International Agency for Research on Cancer (IARC) has evaluated cancer deaths caused by particulate pollution, and the results have shown an increased risk of lung cancer with increasing levels of exposure to particulate matter and air pollution. Although the composition of air pollution and levels of exposure can vary dramatically between locations, IARC indicated that the conclusions apply to all regions of the world [
In the U.S, research on the health effects of particular matter has caused a revision to the National Ambient Air Quality Standards (NAAQS). During this revision, new pollutants with a diameter less than 2.5 μm, commonly called PM2.5, are now regulated. In 2006, the U.S. EPA reissued their fine particle standard to a reduced level of 35 μg/m3 [
An ecologic study performed by Nawrot et al. using data from 15 countries in Europe reported a correlation between PM2.5 and lung cancer mortality among men, but not women [
In a study carried out in the United Kingdom, Harrison et al. tested whether exposure to known chemical carcinogens in the atmosphere was capable of explaining the association between concentrations of PM2.5 and lung cancer mortality observed in the extended ACS Cohort Study [
A recent research carried out by a European consortium reported findings about air pollution and lung cancer incidence in 17 European cohorts. This study showed an association between exposure to particulate matter air pollution and the incidence of lung cancer, in particular adenocarcinoma, in Europe, adding substantially to the weight of the epidemiological evidence [
There is always concern about pollution in the developing world, where data is not comprehensive enough to carry out statistically robust studies. In China, there is a lack of systematic research on the effect of PM2.5 pollutants on lung cancer incidence rates. This is largely because the health impact of PM2.5 pollutants became a concern to the general public only after 2008, when the U.S. Embassy in Beijing began posting PM2.5 data. Most of the studies in China about the risk of exposure to PM2.5 are from data collected in a short period of time. However, studies from western countries suggest that long-term exposure may be more important to analyze to understand the public health implications.
Impact of PM2.5 concentration on lung cancer rate. Note: data cited from reference 20
Average PM2.5 concentration in different cities on April 14, 2014
Experts in China have differing views on the linkage between smog and lung cancer. Some argue that whether the PM2.5 pollution in Beijing is leading to increased lung cancer cases is uncertain because local scientific research is lacking and that at least 10 years of data is needed to prove a causal link to lung cancer. However, this paper believes that evidence from decades of research from western countries can be utilized.
As described in Section 3.1.1, the IARC study showed an increasing risk of lung cancer with increasing levels of exposure to particulate matter and air pollution. Although the composition of air pollution and levels of exposure can vary dramatically between locations, the conclusions of the Working Group apply to all regions of the world [
China has just begun monitoring PM2.5 pollutant levels and currently, there is no research data that correlates PM2.5 pollution with various health issues. However in 2011, the China Daily newspaper reported that the lung cancer rate in Beijing had increased 60% over the past decade, even as levels of smoking had fallen, implying air pollution as a primary culprit for the increased cancer rate [
Beijing health authorities have launched a pilot project to test for the rate of cancers in the city. The project was announced after the Beijing Health Bureau released a list of the top five highest incidence cancers in Beijing. The rate of lung cancer is the highest of all cancer types, and smog and smoking have been specifically cited as causes [
A joint study by Greenpeace East Asia and Beijing University’s School of Public Health estimates that PM2.5 pollution caused the cities of Shanghai, Guangzhou, Xi’an and Beijing a combined total of US $1.1 billion in economic losses over the past year. Greenpeace is calling for an urgent policy adjustment, including capping regional coal consumption, retrofitting De-NOx for existing coal-fired power plants, and shutting down inefficient coal-fired industrial boilers. The report, “PM2.5: Measuring the Human Health and Economic Impacts on China’s Largest Cities”, states that if these cities can effectively lower their PM2.5 levels to meet the World Health Organization’s Air Quality Guidelines, then premature deaths could be reduced by at least 81%, and economic losses for these four cities could be reduced by US $868MM [
PM2.5 has not been limited to China—many other countries have experienced the same set of effects during their industrial growth periods. A research report comparing European and U.S. approaches towards controlling PM2.5 pollution shows that in most western countries in the 1990’s, the main contributors to PM2.5 pollutants were stationary combustion, industrial processes, transportation and agriculture [
Davison et al. reported that concentrations of toxic elements in fly ash from coal fired power stations increased markedly with decreasing particle size [
The extended ACS cohort study provides an unequivocal message that long term exposure to PM2.5 particulate matter leads to increased mortality due to lung cancer [
Many researchers indicate a substantial latency period between commencement of exposure and the expression of cancer. Research on how to prevent the lung infection by PM2.5 pollutants from developing into lung cancer is important. Clinical research has just started in City of Xian in China to understand the mechanistic interaction between particulates and lung diseases [
The findings of this study provide strong evidence from western countries that long-term exposure to fine particulate air pollution is an important risk factor for lung cancer. Evidence from studies in the U.S. and Europe has clearly shown that elevated fine particulate air pollution exposures are associated with an increase in lung cancer
. PM2.5 standard adopted by different countries
Country | Annual Average μg/m3 | 24 hours Average μg/m3 | Date of Implementation |
---|---|---|---|
U.S. | 15 | 35 | December 17, 2006 |
EU | 25 | NA | Issued January 1, 2010. Fully implementation on January 1, 2015 |
Japan | 15 | 35 | September 9, 2009 |
China | 35 | 75 | Effective 2016 (Public hearing period) |
WHO | 10 | 25 | Highly recommended |
mortality. While many uncertainties remain, it appears plausible that known chemical carcinogens are responsible for the lung cancer cases attributed to PM2.5 exposure. Therefore, China should focus efforts not on verifying western countries’ research findings, but on controlling PM2.5 pollutants and conducting research on preventing and curing lung cancers caused by PM2.5 pollution. In China, classifying PM2.5 pollution as carcinogenic to humans is an important first step. There are effective ways to reduce particulate air pollution and, given the scale of the exposure affecting people worldwide, this study suggests that China should take action without further delay.