Air Pollution's Cancerous Impact: Understanding The Risk

Air pollution is a significant and far-reaching threat to public health, with 99% of the world's population breathing unhealthy air, according to the World Health Organization (WHO). Exposure to air pollution can lead to lung cancer, stroke, respiratory and cardiovascular diseases, and other health issues. While cigarette smoking accounts for more than 80% of lung cancers, a substantial number of lung cancer cases are observed among non-smokers, and air pollution is the second-leading cause of lung cancer. Studies have also found links between air pollution and other types of cancer, including breast, liver, and pancreatic cancer. Overall, air pollution causes up to 29% of all lung cancer deaths and is estimated to cause nearly seven million deaths per year.

Lung cancer

Air pollution is a significant contributor to lung cancer cases and deaths worldwide. Fine particulate matter, known as PM2.5, is a mix of solid particles and liquid droplets with a diameter of less than 2.5 micrometers. These particles can penetrate deep into the lungs and even enter the bloodstream, causing inflammation and damage that can lead to lung cancer. According to the World Health Organization (WHO), nearly half of lung cancer cases in non-smokers are related to air pollution. Additionally, air pollution is estimated to cause nearly seven million deaths per year, with low- and middle-income countries bearing the heaviest toll.

In 2013, the International Agency for Research on Cancer (IARC) classified outdoor air pollution and particulate matter (PM) as Group 1 human carcinogens for lung cancer. This classification was based on extensive research and evidence from studies of humans and experimental animals. The Global Burden of Disease 2019 study estimated that 15% of global lung cancer deaths were attributable to PM2.5 in outdoor air. This percentage is even higher in certain countries, such as China, where air pollution is a significant concern due to industrialization and a large population.

The sources of air pollution contributing to lung cancer vary and include vehicle exhaust, coal-fired power plants, industrial sources, wildfires, wood-burning stoves, and construction sites. These sources release harmful pollutants such as acids, heavy metals, and organic chemicals into the air, which can have detrimental effects on human health. While the use of personal respirators and household filtration systems can help reduce exposure to PM2.5, more comprehensive interventions are needed to address this global health issue.

It is important to note that air pollution not only contributes to lung cancer but also interferes with cancer treatments. It can reduce the effectiveness of chemotherapy drugs, increase surgical complications, and negatively impact immunotherapies. The global cost of health damages associated with air pollution is estimated at USD 8.1 trillion, emphasizing the urgency of addressing this public health crisis.

Outdoor air pollution

Numerous epidemiological studies have investigated the link between outdoor air pollution and cancer. The International Agency for Research on Cancer (IARC) classified outdoor air pollution and PM2.5 as Group 1 human carcinogens for lung cancer in 2013. This classification was based on extensive evidence from human and animal studies, as well as strong mechanistic insights. Large-scale cohort studies, such as the American Cancer Society's Cancer Prevention Study-II (CPS-II) and the European Study of Cohorts for Air Pollution Effects (ESCAPE), provided valuable insights by evaluating a broad range of exposures and potential confounders, including cigarette smoking.

The association between outdoor air pollution and lung cancer has been observed in Europe, North America, Asia, and Oceania. People living in highly polluted areas have a higher risk of dying from lung cancer. Outdoor air pollution increases the risk of lung cancer in both sexes and across all geographic regions. Additionally, it has been linked to approximately 1% of all cancer cases in Europe and causes about 2% of cancer-related deaths. For lung cancer specifically, outdoor air pollution contributes to around 9% of deaths in Europe.

The health impacts of outdoor air pollution are not limited to lung cancer. Studies suggest that air pollution is associated with an increased risk of mortality for various cancer types, including breast, liver, and pancreatic cancer. Furthermore, air pollution may interfere with cancer treatments, reducing the effectiveness of chemotherapy drugs and complicating surgeries and targeted therapies. Overall, outdoor air pollution is a significant contributor to cancer cases and deaths worldwide, underscoring the urgent need for preventive measures and interventions.

Indoor air pollution

Air pollution is a significant public health concern, causing nearly seven million deaths per year. According to the World Health Organization (WHO), 99% of the world's population breathes unhealthy air. While outdoor air pollution is a major contributor to this issue, indoor air pollution also poses serious risks, especially in households that rely on solid fuels for cooking and heating.

Particulate matter, specifically PM2.5, has been a focus of concern in indoor air pollution. PM2.5 refers to tiny airborne particles with an aerodynamic diameter of less than 2.5 micrometres, small enough to penetrate deep into the lungs and even enter the bloodstream. Sources of indoor PM2.5 can include cooking fumes, smoke from solid fuel combustion, second-hand tobacco smoke, and emissions from unvented or inefficient heating sources. High levels of PM2.5 exposure have been linked to an increased risk of lung cancer, as well as other types of cancer, including breast, liver, and pancreatic cancer.

The use of solid fuels for cooking and heating is a significant contributor to indoor air pollution, particularly in low- and middle-income countries. Women and children, who typically spend more time indoors and are often responsible for cooking, are disproportionately affected by this type of pollution. The World Health Organization (WHO) has developed tools to address indoor air pollution, such as the AirQ+ software, which assesses health risks associated with air pollution, and the Carbon Reduction Benefits on Health (CaRBonH) tool, which helps governments quantify the benefits of improving air quality.

Reducing indoor air pollution is crucial to mitigate its adverse health effects. This can be achieved through various interventions, including improved ventilation, the use of cleaner fuels, and the adoption of household filtration systems. Additionally, behavioural changes, such as avoiding indoor smoking and ensuring proper maintenance of combustion appliances, can also help reduce exposure to indoor air pollutants. By addressing indoor air pollution, we can decrease the cancer risk associated with this preventable environmental factor.

Air pollution and cancer treatment

Air pollution is a significant and far-reaching public health threat, with 99% of the world's population breathing unhealthy air, according to the World Health Organization (WHO). It is a major contributor to the global disease burden, causing nearly seven million deaths per year, a figure comparable to excess mortality from COVID-19 in 2020 and 2021. Low- and middle-income countries bear the brunt of these premature deaths, with nearly 90% occurring in these regions.

Outdoor air pollution, particularly particulate matter (PM), has been linked to lung cancer incidence and mortality. In 2013, the International Agency for Research on Cancer (IARC) classified outdoor air pollution and PM as Group 1 human carcinogens for lung cancer. This classification was based on extensive evidence from human and animal studies, as well as mechanistic insights. Lung cancer is the most commonly diagnosed cancer globally, with an estimated 2.1 million new cases and 1.8 million deaths in 2018. While cigarette smoking accounts for over 80% of lung cancers, a substantial number of cases occur in non-smokers, and air pollution is a significant factor. Air pollution alone causes up to 29% of all lung cancer deaths, and nearly half of lung cancer cases in non-smokers are attributed to it.

In addition to lung cancer, air pollution is associated with an increased risk of other types of cancer. A 2020 study found a link between long-term exposure to ambient fine particulate matter (PM2.5) and higher mortality rates from breast, liver, and pancreatic cancer. Another study suggested that air pollution could affect gut microbiota, influencing the development of cancers in the digestive organs. While pollution is one risk factor, others like diet and exercise may have a more significant impact on cancer risk.

Air pollution also negatively impacts the quality of life for people living with cancer. It exacerbates respiratory symptoms, increases fatigue, reduces physical activity, and worsens treatment side effects. Additionally, it may interfere with cancer treatments, reducing chemotherapy drug effectiveness, increasing surgical complications, and potentially interacting with targeted and immunotherapies. The global health damages associated with air pollution exposure are estimated at USD 8.1 trillion, equivalent to 6.1% of global GDP, according to the World Bank.

To address this pressing issue, governments worldwide have recognized the adverse effects of household and ambient air pollution. However, progress in reducing air pollution has been uneven. While 6,000 cities in 117 countries now monitor air quality, none of the world's 100 largest cities meet WHO air pollution guidelines. Individual-level interventions, such as the use of personal respirators and avoidance behaviours, can help reduce exposure to PM2.5, but the overall evidence for their effectiveness is still inadequate.

Air pollution and genetics

Air pollution is a significant and far-reaching threat to public health, with 99% of the world's population breathing unhealthy air. It has been linked to lung cancer and is also associated with an increased risk of mortality from other types of cancer, including breast, liver, and pancreatic cancer. Outdoor air pollution and fine particulate matter (PM2.5) have been classified as Group 1 human carcinogens for lung cancer.

Genetic susceptibility is likely a factor in the response to air pollution exposure. Some individuals may be genetically predisposed to the adverse effects of air pollutants due to variations in genes involved in the biological response to these toxins. For example, studies have identified genes such as tumor necrosis factor-α (TNF) and Toll-like receptor 4 (TLR4) that play a role in respiratory responses to ozone, a component of air pollution.

Additionally, air pollution has been linked to epigenetic modifications, which are heritable changes in gene expression that do not alter the DNA sequence. These modifications can influence the regulation of different genomic functions and may impact an individual's vulnerability to environmental insults or genetic variants. For instance, air pollution exposure has been associated with DNA methylation (DNAm) changes, which could influence inflammation, disease development, and exacerbation risk.

While the exact number of cancer cases directly attributed to air pollution may be challenging to determine due to various confounding factors, the available evidence suggests a significant association between air pollution and cancer risk. Further research and interventions are necessary to address this global health concern effectively.

In summary, air pollution poses a severe threat to public health, and its link to cancer development is well-established. Genetic factors play a crucial role in determining individual responses to air pollution exposure, and epigenetic modifications induced by air pollutants can have intergenerational impacts. Understanding the complex interaction between air pollution and genetics is essential for developing effective prevention strategies and interventions to mitigate the adverse effects of air pollution on human health.

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