Air Pollution: A Major Cause Of Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide, with approximately 1.8 million deaths annually. While smoking is a significant contributor to lung cancer, air pollution is also a critical factor. Outdoor air pollution, particularly particulate matter (PM) with an aerodynamic diameter of less than 2.5 micrometers (PM2.5), has been classified as a Group 1 human carcinogen for lung cancer by the International Agency for Research on Cancer (IARC). These fine particles can enter deep into the lungs and are linked to lung cancer, with increasing PM2.5 levels associated with a higher risk of developing lung cancer. Evidence suggests that air pollution can cause cancerous changes in airway cells, especially in individuals with specific gene mutations. Additionally, indoor air pollution, such as radon and second-hand smoke, also contributes to lung cancer risk. While air pollution levels vary globally, reducing air pollution is crucial to lowering the incidence and mortality of lung cancer.

Particulate matter (PM) in the air increases the risk of lung cancer

Particulate matter (PM) in the air is a human lung carcinogen, and exposure to it increases the risk of lung cancer. PM is a mix of tiny solid and liquid particles in the air, including acids, organic chemicals, metals, soil, and dust particles. These particles are often so small that they are invisible, but when their levels are high, they cause the air to become hazy and thick. PM2.5, which has a diameter of less than 2.5 micrometers, is particularly harmful as it can enter deep into the lungs and carry toxic substances such as sulfates, organic compounds, polycyclic aromatic hydrocarbons, and heavy metals, which are considered major carcinogens.

Studies have shown a positive correlation between increasing PM2.5 concentrations and lung cancer mortality. For every 10 micrograms per cubic meter (µg/m3) of increased exposure to PM2.5, the risk of dying from lung cancer rose by 36%. Long-term exposure to PM2.5, especially in urban areas with high levels of vehicle traffic, has been linked to an increased risk of lung cancer. Traffic-related air pollution (TRAP) is a significant source of ambient PM, and vehicle emissions contain various chemical components, including known or suspected carcinogens such as PAHs, benzene, formaldehyde, and heavy metals.

In addition to vehicle emissions, human activities and natural sources emit gases that react in the air to form particles. For example, the combustion of carbon-based fuels generates most of the fine particles in our atmosphere. Burning wood, wildfires, agricultural fires, and the burning of fossil fuels in factories, power plants, and vehicles all contribute to PM. Even in areas with low air pollution levels, such as the United States, lower levels of particle pollution have been linked to lung cancer.

Certain groups are at higher risk of health problems from breathing in particle pollution, including children, the elderly, people with lung and heart disease, people with low incomes, and those who work or exercise outdoors. To protect themselves, individuals can check the air quality index forecast and limit their activity if pollution levels are high. Additionally, reducing air pollution is crucial to lowering the risk of lung diseases, including cancer. While the specific components of PM responsible for the increased risk of lung cancer have not been definitively identified, the evidence strongly suggests that PM is associated with an increased incidence and mortality of lung cancer.

Exposure to air pollution can cause inflammation in the lungs, leading to cancer

Exposure to air pollution can cause inflammation in the lungs, which can lead to cancer. Fine particles in air pollution can enter deep into the lungs and are linked to lung cancer. Particulate matter (PM), especially PM2.5, is a known cause of non-small cell lung cancer (NSCLC). PM2.5 refers to particulate matter with an aerodynamic diameter of less than 2.5 micrometers, which is approximately 1/30th the width of a human hair.

The World Health Organization (WHO) International Agency for Research on Cancer (IARC) concluded in 2013 that there is sufficient evidence to classify outdoor air pollution and PM in outdoor air pollution as Group 1 human carcinogens for lung cancer. This classification indicates that there is a causal relationship between exposure to these substances and the development of lung cancer. The IARC evaluation considered a broad range of exposures and detailed information on potential confounders, including cigarette smoking.

The mechanisms by which air pollution causes lung cancer are still being investigated. However, it is known that particles linked to climate change can promote cancerous changes in airway cells. Cells with EGFR and KRAS gene mutations are particularly susceptible to turning cancerous when exposed to air pollutants. Additionally, air pollution may spark defects in DNA repair function, alterations in the body's immune response, or inflammation that triggers angiogenesis, the growth of new blood vessels that allow tumors to spread.

The risk of developing lung cancer from air pollution is higher in certain populations, including children, the elderly, people with lung and heart disease and diabetes, people with low incomes, and those who work or exercise outdoors. The number of lung cancer cases attributed to air pollution varies by country, with lower-income countries and countries with large populations often experiencing higher levels of air pollution. For example, in China, air pollution is believed to be responsible for approximately 180,000 lung cancer deaths annually.

While smoking is a more significant risk factor for lung cancer than air pollution, the two factors are synergistic, meaning they can worsen the effects of each other. Therefore, reducing air pollution is crucial in lowering the risk of lung cancer, especially in populations with high smoking rates.

Outdoor air pollution from vehicles, power plants, and industries is linked to lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide, with an estimated 2.1 million new cases and 1.8 million deaths in 2018. Outdoor air pollution, particularly from vehicles, power plants, and industries, is a significant contributor to this alarming statistic.

Vehicle exhaust emissions, coal-fired power plants, and industrial sources release a cocktail of harmful pollutants into the air we breathe. These pollutants include particulate matter (PM), a mix of tiny solid and liquid particles such as acids, organic chemicals, metals, soil, and dust. PM2.5, with an aerodynamic diameter of less than 2.5 micrometers, is of particular concern as it can penetrate deep into the lungs. The health risks associated with PM2.5 exposure are evident, with studies showing that for every 10 micrograms per cubic meter (µg/m3) increase in PM2.5 exposure, the risk of dying from lung cancer rises by 36%.

The link between outdoor air pollution and lung cancer is supported by extensive research. In 2013, the World Health Organization (WHO) International Agency for Research on Cancer (IARC) reviewed the available scientific evidence and concluded that particulate matter, specifically PM2.5, is carcinogenic to humans and a cause of lung cancer. This classification, grouped with other known human carcinogens, underscores the weight of the evidence. The IARC's evaluation was based on informative cohort studies, such as the American Cancer Society (ACS) Cancer Prevention Study-II (CPS-II) and the European Study of Cohorts for Air Pollution Effects (ESCAPE), which provided valuable insights into the long-term effects of outdoor air pollution exposure.

The harmful effects of outdoor air pollution are not limited to lung cancer. Studies have suggested that air pollution is associated with an increased risk of mortality for several other types of cancer, including breast, liver, and pancreatic cancer. Additionally, air pollution can worsen lung cancer survival rates and increase the overall risk of premature death, heart disease, and asthma attacks. It can also interfere with lung development and function, impacting the health and quality of life for people of all ages.

To address these pressing health concerns, it is imperative to advocate for measures that reduce outdoor air pollution. This includes regulating emissions from vehicles, power plants, and industries, as well as promoting sustainable practices and alternative energy sources. Individual actions, such as reducing personal vehicle usage and supporting initiatives to improve air quality, can also contribute to mitigating the harmful impacts of outdoor air pollution on lung cancer incidence and overall public health.

Air pollution interacts with smoking, worsening lung cancer survival rates

Air pollution and smoking are the two leading causes of lung cancer. While the risk of lung cancer from air pollution is lower than from smoking, the former is an issue that is beyond the control of individuals. Globally, more people are exposed to unsafe levels of air pollution than to toxic chemicals in cigarette smoke.

Air pollution is known to cause many health hazards and can contribute to the development of lung cancer and worsen its prognosis. Fine particles from air pollution can enter deep into the lungs and are linked to lung cancer. These particles are typically found in vehicle exhaust and smoke from fossil fuels. They are associated with non-small cell lung cancer (NSCLC) risk, accounting for over 250,000 lung cancer deaths globally per year.

In a study of nearly half a million people living in England, South Korea, and Taiwan, exposure to increasing concentrations of airborne particulate matter (PM) of 2.5 micrometres (PM2.5) in diameter was linked to an increased risk of NSCLC with EGFR mutations. PM2.5 can also come from events worsened by climate change, such as wildfires and sandstorms. PM2.5 from wildfires is up to 10 times more harmful to human health than PM2.5 from other sources due to its higher carbon content and oxidative potential.

The number of estimated attributable lung cancer deaths has increased by nearly 30% since 2007 as smoking has decreased and air pollution has increased. While smoking-related lung cancers are projected to decrease in the next 25 years as smoking rates continue to decline, the proportion of lung cancers in people who have never smoked will continue to increase.

Indoor air pollution, like secondhand smoke and radon, also increases lung cancer risk

While outdoor air pollution from sources such as vehicle exhaust, coal-fired power plants, and industrial sources is a well-known cause of lung cancer, indoor air pollution also plays a significant role in increasing lung cancer risk. Indoor air pollutants like secondhand smoke and radon should not be overlooked, as they can have detrimental effects on the health of individuals, especially those who are frequently exposed to them.

Secondhand smoke, also known as environmental tobacco smoke, is a significant indoor air pollutant that increases the risk of lung cancer in non-smokers. Non-smokers who are regularly exposed to secondhand smoke have a 20-30% higher risk of developing lung cancer. This risk is not limited to adults; even infants and children are susceptible to the harmful effects of secondhand smoke. Infants exposed to secondhand smoke are at an increased risk of sudden infant death syndrome (SIDS), and children may experience respiratory infections, ear infections, and asthma attacks. Moreover, secondhand smoke exposure during pregnancy has been linked to adverse outcomes such as reduced fertility, pregnancy complications, impaired lung development, and low birth weight.

The harmful effects of secondhand smoke are not limited to lung cancer. It also increases the risk of other cancers, including breast cancer, nasal sinus cavity cancer, and nasopharyngeal cancer in adults, as well as leukemia, lymphoma, and brain tumors in children. The immediate impact of secondhand smoke exposure on the body includes airway irritation and detrimental effects on the heart and blood vessels, increasing the risk of heart disease.

Radon is another critical indoor air pollutant that contributes to lung cancer risk. It is a colorless, odorless, and radioactive gas released from soil or rock. Long-term exposure to radon can lead to lung cancer, as the radioactive particles released during its decay can damage the cells lining the lungs. While cigarette smoking is the most common cause of lung cancer, radon is the second leading cause in the United States. Exposure to both radon and cigarette smoke significantly increases the risk of lung cancer compared to exposure to either factor alone. Scientists estimate that lowering radon levels in homes exceeding the EPA's action level of 4 picocuries per liter (pCi/L) could reduce lung cancer deaths by 2 to 4 percent, equivalent to about 5,000 lives saved annually.

The impact of indoor air pollution on lung cancer risk underscores the importance of maintaining good indoor air quality, particularly in homes and public spaces. By understanding the risks associated with indoor air pollutants like secondhand smoke and radon, individuals can take preventive measures to reduce their exposure and mitigate the potential harm to their health.

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