A recent global study reveals that individuals who have never smoked are now responsible for a higher number of lung cancer diagnoses compared to those who have a smoking history.

Researchers from around the world have discovered that the predominant form of the disease is currently adenocarcinoma – a kind of lung cancer that develops in the linings of the organs and is predominantly seen in individuals who do not smoke.

This type of cancer has surpassed other lung cancer variations like squamous cell carcinoma and small-cell carcinoma, which are usually brought on by the carcinogenic substances in cigarettes, including tar.

The experts behind the research, from China and France, believe increasing exposure to air pollution could be responsible. 

They estimated that around a third of the 600,000 adenocarcinoma cases diagnosed each year globally could be attributed to air pollution.

The scientists said even a small amount of exposure to pollution from traffic and burning fossil fuels could increase the risk of adenocarcinoma by over 50 per cent.

The experts also noted that as per 2019 reports, 99 per cent of the global population live in areas where air quality doesn’t meet World Health Organisation (WHO) standards. 

Examining lung cancer trends across the globe, they found the risk of air pollution-related adenocarcinoma is particularly high in China, which is famous for its cities blanketed by smog. 

Patients who have never smoked now make up an increasing number of global lung cancer cases, and air pollution may be to blame, a global analysis suggests 

While men still accounted for the majority of lung cancer cases, the authors noted adenocarcinoma was more prevalent among women.

The experts suggested this may be due to increased exposure to the pollution caused by indoor cooking. In countries such as China, women are frequently exposed to the effects of solid cooking fuels, including coal. 

They concluded that that as smoking rates decline, examining how lung cancer emerges among never-smokers becomes increasingly important.

Only about a fifth adults worldwide now use tobacco products like cigarettes, compared to a third in 2020 according to WHO estimates. 

The researchers called for further research to examine exactly how air pollution may trigger changes in the cells of the lungs that go on to become cancer. 

Some experts theorise that microscopic particles of pollution enter the lungs where they damage cells’ DNA, leading to the rapid division of cells that causes cancerous tumours to form.

Lung cancer kills some 35,000 Brits each year, about four every hour. However, rates of the disease have declined some 9 per cent since 90s across the population as a whole 

Others suggest it could be due to the body’s reaction to pollution particles, such as inflammation, which activates dormant mutations within cells that go on to cause the disease. 

The study, published in The Lancet Respiratory Medicine, has some limitations which the authors acknowledged.

Firstly, their data was collated from national cancer registries meaning there may be some inconsistencies in lung cancer diagnoses between different nations.

Their findings come as the UK has seen its own rise in lung cancer cases among young women and girls.

Figures from Cancer Research UK (CRUK) show cases of the disease has risen by 130 per cent in females under 24-years-old over the past few decades.

This makes them the fastest growing group at risk of the disease — although over-70s are still most likely to be diagnosed. 

In contrast, rates among men of the same age have barely budged from the early 90s, for reasons that medics say are simply unknown. 

Cancer experts have warned against viewing lung cancer as ‘an old person’s disease’ — as it was previously seen. 

Young women were also urged not to dismiss a persistent cough — the main symptom of the disease — at this time of year, when colds are rife.  

Experts told MailOnline one of the reasons for alarm, and as identified in the recent study, is that many of these cases are among women who have never smoked. 

Cancer experts have now warned against viewing lung cancer as ‘an old person’s disease’ — as it was previously seen. Young women were also urged not to dismiss a persistent cough — the main symptom of the disease — at this time of year, when colds are rife

This means it is almost impossible for medics to provide any advice on how younger women can minimise their risk. 

Lung cancer kills some 35,000 patients in Britain each year, about four every hour, making it the largest cause of cancer death in the UK.

Symptoms of lung cancer include a persistent cough that doesn’t go away after three weeks, repeated chest infections, coughing up blood, pain while breathing, persistent breathlessness and fatigue, and unexpected weight loss.  

Other, more unusual signs of lung cancer include change in the appearance of your fingers, difficulty or pain swallowing, wheezing, changes in your voice, and swelling of the face or neck.

Anyone with any of these signs is urged to see their GP.