Lung Cancer in Non-Smokers: Air Pollution as a Trigger

Before we look into air pollution as a trigger for lung cancer in non-smokers, it’s important to differentiate between the types of lung cancer.

The distinction between the main types of cancer is made under the microscope, examining the cellular characteristics that differentiate them. Small-cell lung cancer is characterized by smaller cells that grow and spread quickly. The non-small cell type has larger cells that slowly grow and comprise about 85% of all lung cancers. A subtype of non-small cell cancer is adenocarcinoma which represents 35-40% of all lung cancers.

Adenocarcinoma in non-smokers

Adenocarcinoma is typically found in non-smokers. Usually, it is located in a peripheral location within the lung, usually around the edges. It arises from the bronchial mucosal glands or the lining of the bronchi - the tubes which connect your windpipe to your lungs. Adenocarcinoma can also occur at the site of previous scars, wounds, or inflammation. Hence, it is often called “scar carcinoma.”

Surprisingly, 20% of people in the United States who die from lung cancer - roughly 30,000 people each year - have never smoked.

Main causes of lung cancer other than smoking

The American Cancer Society lists the following environmental risk factors which could contribute to a lung cancer diagnosis in non-smokers:

Radon exposure

This exposure can cause lung cancer in non-smokers. It accounts for close to 21,000 lung cancer deaths per year. The gas is invisible and doesn’t have a smell but is naturally occurring and its levels are usually higher in basements, cellars, and grounded living spaces.

Secondhand smoke

Inhaling the smoke of others has been linked to an estimated 7,000 lung cancer deaths each year in the United States.

Cancer-causing agents at work

These include asbestos, heavy metals, inorganic arsenic, and diesel fumes. They are especially concerning to those regularly exposed to workplace carcinogens.

Atmospheric pollution

There are strong links between air pollution (indoor and outdoor) and lung cancer. Many countries, such as the U.S., have strict air pollution regulations, but there are plenty of places worldwide that are unregulated.

Are lung cancer diagnoses on the rise?

In a United States study, rates of lung cancer in non-smokers increased from 8.9% in the period 1990-95 up to 19.5% in 2011-13. Another study conducted in the United Kingdom reported an increase from 13% to 28% during 6 years.

Because not all smokers develop lung cancer and not all lung cancer patients have a history of smoking, other factors are often implicated. Genetic susceptibility, carcinogen exposure, and other environmental risk factors are thought to play a role independently or in conjunction with smoking.

Genetic factors likely contribute to all lung cancers, but the susceptibility to factors other than smoking is population-specific. Some areas of the world have higher exposure rates to air and environmental pollutants than others.

Symptoms of lung cancer in people who have never smoked

Most people who develop lung cancer have similar symptoms whether they smoke or not. Unfortunately, many who have these symptoms let their disease progress to more advanced stages since they have never smoked, and lung cancer is not something they think could affect them.

Symptoms that are not lung related could indicate a local or regional spread of the disease so it’s important to consider them. Noting that people with adenocarcinoma who were non-smokers tend to develop cancer at the edges of their lungs, and may be more likely to display non-lung related ailments.

Also, it’s important to acknowledge the vast array of neurologic signs which may include any or all of the following:

What is the screening process for lung cancer?

Screening is the means of testing for lung cancer when there are no symptoms or history of the disease. A recommended screening test for lung cancer is a low-dose computed tomography (CT scan).

Surprisingly, the U.S. Preventive Services Task Force does not recommend lung cancer screening for people who have never smoked. There are possible harms of screening which include:

A false positive result

This means the test suggests that the person has lung cancer when no cancer is present.

Overdiagnosis

This means the test finds cases of cancer that may never have caused a problem for the patient.

Radiation exposure

Repeated tests such as X Rays can cause cancer in otherwise healthy people.

How can I help lower my risk of getting lung cancer?

The most helpful advice is to not smoke (or stop smoking) and avoid secondhand smoke as much as possible.

Other risk factors to avoid include:

• Diesel exhaust.
• Air pollution.
• Radon - assess your home for radon levels.

Another factor to consider is genetics. Personal or family history of lung cancer can be a factor in developing lung cancer. People who develop lung cancer and have never smoked may have a genetic or DNA mutation. These genetic mutations must be treated with targeted therapy, meaning that the treatment must be specifically aimed at the cause.

What affects the prognosis or chance of recovery in people with lung cancer?

The prognosis and treatment options depend on the following:

The stage of cancer (the size of the tumor and whether it is in the lung only or has spread to other places in the body).

The type of lung cancer.

Whether cancer has mutations (changes) in certain genes, such as the epidermal growth factor receptor (EGFR) gene or the anaplastic lymphoma kinase (ALK) gene.

Whether there are signs and symptoms such as coughing or trouble breathing.

The patient’s general health.

The latest evidence that air pollution contributes to lung cancer

Researchers attending the recent European Society of Medical Oncology Congress in September 2022 presented some alarming findings. They studied the effects of pollution on 400,000 people from the UK and Asia to investigate the association between lung cancers and the mutant EGFR gene in those who had never smoked.

The research found that air pollution may cause other cancers to develop as well as mesothelioma or cancer of the lining of the lungs. These findings have global implications as almost 99% of the world’s population lives in areas that may exceed acceptable levels of air pollution.

The researchers are currently studying the mechanisms by which genetic mutations lead to cancer in people exposed to air pollutants. It is believed that there will be new ways to prevent and treat lung cancer in patients who have never smoked. The goal of new cancer therapy is to stop the cells from growing in response to air pollution and therefore reduce the risk of lung cancer.

The most urgent preventative measure suggested by the study findings is to reduce air pollution on a global scale to safeguard public health.