Even low level exposure to traffic fumes can increase the risk of lung cancer, a large study has found.

Air pollution may have to be added to smoking as a recognised cause of the disease, it is claimed.

Lung cancer is the biggest cancer killer in the UK, claiming almost 35,000 lives in 2010. In the same year, 42,000 Britons were diagnosed with the disease.

An estimated 86% of cases are believed to be a direct result of smoking. Other potential triggers include exposure to natural radioactive gas from the ground and toxic substances in the work place, such as asbestos.

The new research, jointly led by experts at Edinburgh University, reported in the journal The Lancet Oncology, analysed pooled information from 17 studies in nine European countries.

Air pollution levels were estimated at people's home addresses and cancer diagnosis rates obtained from national and local registries. Over an average 13 year follow-up period, 2095 study participants developed lung cancer.

People's chances of having the disease rose with greater exposure to small sooty particles generated by diesel exhausts which are known to lodge in the lungs.

Traffic pollution was mostly linked to adenocarcinoma lung cancer, the only form of the disease to affect significant numbers of non-smokers.

Commenting in the journal, Japanese expert Dr Takashi Yorifuji from Okayama University wrote: "At this stage, we might have to add air pollution, even at current concentrations, to the list of causes of lung cancer and recognise that air pollution has large effects on public health."