Air Pollution's Cancerous Impact: Australian Insights

Air pollution is a major contributor to the global burden of disease, with 99% of the world's population breathing unhealthy air. Outdoor air pollution is a significant cause of lung cancer, with fine particulate matter (PM2.5) from sources such as vehicle exhaust, coal-fired power plants, and industrial emissions penetrating deep into the lungs and even entering the bloodstream. While smoking remains the biggest risk factor for lung cancer, air pollution is the second leading cause, and in 2017, it was responsible for approximately 265,267 lung cancer deaths worldwide. In Australia, a study in Perth, Western Australia, found positive associations between air pollution and lung cancer, suggesting that there is no safe level of air pollution when it comes to carcinogenic risk.

Air pollution and smoking are synergistic

Air pollution and smoking are two of the leading preventable causes of death globally. While smoking remains the biggest risk factor for lung cancer, outdoor air pollution causes roughly 1 in 10 cases of lung cancer in the UK. In Australia, a study in Perth found positive associations between air pollution and lung cancer, observing 692 (6.0%) lung cancer events during the study period.

Several studies have investigated the synergistic effects of air pollution and smoking on pulmonary function. One such study in Beijing examined a random sample of 3287 adults aged 40-69 who lived in residential, industrial, and suburban areas. The study found that long-term exposure to high levels of particulate matter and sulfur dioxide was associated with significantly reduced pulmonary function in both smokers and never-smokers. However, the associations were significantly greater among smokers, indicating a synergistic effect of air pollution and smoking on adult pulmonary function.

Another study in Hong Kong found that ever-smokers were more susceptible to excess mortality risk associated with daily air pollution, especially males, overweight or obese elders, and those with poor health conditions or lower educational attainment. Tobacco control measures can help reduce the health burdens attributable to air pollution, as smoking history has been shown to modify the association between short-term exposure to air pollution and mortality.

While the exact mechanisms of the synergistic effects of air pollution and smoking are still being elucidated, it is clear that the combination of these two factors poses a significant risk to respiratory health and mortality. Further research is needed to fully understand the carcinogenic potential of ambient air pollution, especially at low concentrations, and to develop effective strategies to mitigate its impact on public health.

Outdoor air pollution

Advocating for lower sources of exposure to air pollution is crucial. Healthcare institutions, for instance, can reduce their environmental footprint and become more sustainable, thus lowering their impact on air pollution. Additionally, organisations like the International Association for the Study of Lung Cancer can actively engage in raising awareness and driving change on this topic.

Scientific studies have provided valuable insights into the relationship between outdoor air pollution and lung cancer. Research has identified a link between fine particulate matter (PM2.5), nitrogen dioxide, and black carbon (BC) and lung cancer. These pollutants are known to cause inflammation in the lungs, which can lead to cancer. It is important to note that the risk of lung cancer from air pollution is not limited to smokers; even individuals who have never smoked can develop lung cancer due to air pollution exposure.

In 2013, the International Agency for Research on Cancer classified outdoor air pollution as carcinogenic to humans, specifically highlighting particulate matter with an aerodynamic diameter of less than 2.5 microns. This classification further emphasises the role of outdoor air pollution in causing lung cancer. The number of estimated lung cancer deaths attributed to air pollution has been increasing, with a nearly 30% rise since 2007, while smoking rates have been decreasing during the same period.

While the exact mechanisms by which air pollution triggers lung cancer are still being investigated, studies have revealed that air pollution can activate cancer-causing mutations in lung cells, encouraging the growth and potential formation of tumours. Additionally, higher rates of EGFR mutant lung cancer have been observed in individuals living in areas with elevated levels of PM2.5 pollution. This knowledge underscores the urgent need to address outdoor air pollution and implement preventive measures to protect public health.

Indoor air pollution

While outdoor air pollution is a well-known cause of lung cancer, indoor air pollution also plays a significant role in increasing lung cancer risk. Household air pollution (HAP) from the use of solid fuels for cooking and heating is a major concern, with about half of the world's population exposed to it. In 2012, HAP was estimated to have caused 4.3 million deaths, accounting for 7.7% of global mortality.

Studies have found a strong link between indoor air pollution and lung cancer, especially in never-smoking women. In Xuanwei County, China, where lung cancer rates among never-smoking women are among the highest globally, the use of smoky coal instead of smokeless coal was associated with a 99-fold increase in lung cancer risk. This is one of the most striking examples of the impact of indoor air pollution on cancer risk.

In Australia, studies have focused on the impact of indoor and outdoor air pollution on lung cancer risk in older men in Perth, Western Australia. While the relationship between air pollution and lung cancer in low-pollution regions is not yet clear, positive associations have been observed between lung cancer and exposure to PM2.5 and BC. These studies highlight the need for accurate air pollution monitoring and tighter air quality management to reduce the risk of lung cancer associated with indoor air pollution.

PM2.5 and lung cancer

Outdoor air pollution is a cause of lung cancer, and it is estimated to be responsible for roughly 1 in 10 cases of lung cancer in the UK. In 2013, the International Agency for Research on Cancer classified outdoor air pollution and particulate matter with an aerodynamic diameter of less than 2.5 microns as carcinogenic to humans and a cause of lung cancer.

PM2.5, or fine particulate matter, is a type of air pollution with particles that are around 3% of the width of a human hair. It is released from vehicles, industrial processes, and household sources. While smoking remains the biggest risk factor for lung cancer, air pollution is also a significant contributor, and studies have found higher rates of EGFR mutant lung cancer in people living in areas with higher levels of PM2.5 pollution.

One theory suggests that PM2.5 causes inflammation in the lungs, which can lead to cancer. Cells with cancer-causing mutations accumulate naturally as we age but remain inactive. Air pollution is believed to activate these cells, encouraging them to grow and potentially form tumours.

Several studies have investigated the impact of PM2.5 exposure on the survival of lung cancer patients after lobectomy, the primary treatment for early-stage lung cancer. These studies found that an increase in monthly PM2.5 concentration in the months after lobectomy was associated with an increased risk of death. Patients living in areas with high PM2.5 levels should be offered the opportunity to relocate to areas with better air quality after surgery to prolong their survival.

Lung cancer statistics in Australia

While smoking remains the biggest risk factor for lung cancer, air pollution is also a contributing factor. Outdoor air pollution causes roughly 1 in 10 cases of lung cancer in the UK, and an estimated 6,000 people who have never smoked die from lung cancer each year in the UK due to air pollution exposure. In Australia, a study in Perth found that there were 692 (6.0%) lung cancer events identified during the study period, with a total follow-up time of 158,479 person-years. Positive associations between the pollutants and lung cancer were observed, suggesting that there is no known safe level of air pollution as a carcinogen.

The International Agency for Research on Cancer classified outdoor air pollution and particulate matter with an aerodynamic diameter of less than 2.5 microns as carcinogenic to humans and a cause of lung cancer. This particulate matter, known as PM2.5, is believed to cause inflammation in the lungs, which can lead to cancer. Higher rates of EGFR mutant lung cancer have been found in people living in areas with higher levels of PM2.5 pollution.

While the risk of lung cancer from air pollution is lower than from smoking, it is still a significant concern. Lung cancer is the leading cause of cancer mortality worldwide, with more than 1.8 million deaths each year. The five-year net survival rate for lung cancer is also low, ranging from 10% to 20%. As smoking rates decrease, the proportion of lung cancers in people who have never smoked is expected to increase.

In Australia, lung cancer is a significant cause of mortality and morbidity. While specific statistics on the impact of air pollution on lung cancer in Australia are limited, it is clear that air pollution contributes to the overall incidence and mortality of the disease. Further studies are needed to fully understand the carcinogenic potential of ambient air pollution, especially in regions with low pollution levels.

Frequently asked questions