Before we begin looking into how air pollution can be a trigger for lung cancer in non-smokers, it’s important to differentiate between the types of lung cancer.
The distinction between the two types is made under the microscope, examining the clinical 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 are slow growing and comprise about 85% of all lung cancers.
One of the subtypes of non-small cell cancer is adenocarcinoma. Adenocarcinoma is the subtype that represents 35-40% of all lung cancers.
Adenocarcinoma in non-smokers
Adenocarcinoma is typically the lung cancer found in non-smokers. Usually, it occurs in a peripheral location within the lung, meaning out at 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 the “scar carcinoma.”
The surprising statistic is that 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: Exposure to radon 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 usually found outdoors.
Second hand 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, and are of special concern to those who are regularly exposed to carcinogens in the workplace.
Atmospheric pollution: There are strong links between indoor and outdoor air pollution 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% from 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 a 6-year period.
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 causative role, either independently or in conjunction with smoking.
Genetic factors probably contribute to all lung cancers, but the addition of 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 smoked 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 possibly affect them.
Some symptoms are not lung related, and could indicate a local or regional spread of the disease. It’s important to take all symptoms into consideration. 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.
- General fatigue
- Cough, sometimes with blood (hemoptysis)
- Shortness of breath
- Chest pain
- Stridor (upper airway obstruction)
- Heart palpitations
- Weight loss (unexplained)
It’s important to acknowledge the vast array of neurologic signs which may include any or all of the following:
- Arm weakness or numbness
- Eye symptoms like pupil dilation
- Dyspnea (difficult or labored breathing)
- Altered mental status
- Stiff neck
- Nausea and vomiting
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. The only 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 actually cause cancer in otherwise healthy people.
How can I help lower my risk of getting lung cancer?
The most obvious way 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
The other factor is genetic. Personal or family history of lung cancer can be a factor in developing lung cancer.
In fact, people who develop lung cancer and have never smoked may have a genetic or DNA mutation. These types of 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 the 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 the 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 mesothelioma or cancer of the lining of the lungs. These findings have global implications as almost 99% of the world’s population live in areas which may exceed acceptable levels of air pollution.
The researchers are currently studying the mechanisms at which the 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.
Atmospheric pollution has been found to be a causative factor in lung cancer of non-smokers.
Adenocarcinoma is the type of lung cancer typically found in non-smokers.
Reducing exposure to environmental toxins such as second hand smoke is a key preventative measure.
Genetics also play a part in lung cancer susceptibility.
There is new research into treatments aimed at cancer caused by air pollution.
Mayo Clinic. Lung Cancer
Yale Medicine. Lung Cancer in Non-Smokers
MD Anderson Cancer Center. Lung Cancer
MD Anderson Cancer Center. Lung Cancer in Non-smokers: The Latest Research
U.S. Preventative Task Force. Lung Cancer: Screening
National Service Center for Environmental Publications (NSCEP). A Citizen's Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon