IARC finds more cancers linked to tobacco and alcohol

In collaboration with the Press Association

The International Agency for Research on Cancer (IARC) has updated its assessments of several cancer-causing substances and behaviours, which are published in the latest issue of the Lancet Oncology.

A group of 30 leading scientists met at IARC in October 2009 to discuss a number of substances that can cause cancer, including tobacco and alcohol, as well as areca nut and household coal smoke.

This assessment is published as part of the IARC monographs, a series which compiles the available information on all the cancer-causing substances that have been identified so far.

Bowel and ovarian cancers have now been added to the list of cancers caused by tobacco smoking, while recent studies also suggest a small positive association with breast cancer.

Research has also confirmed that parents smoking can cause childhood cancer, with children born to smokers facing a higher risk of a rare form of cancer called hepatoblastoma. There also appears to be an increased risk of leukaemia in children whose fathers smoked before their conception.

Turning to secondhand smoke, the IARC confirms that it can cause lung cancer and notes that there is some evidence for a link between cancers of the larynx and pharynx.

Smokeless tobacco, meanwhile, has now been shown to cause cancers of the oesophagus, as well as mouth and pancreatic cancers.

IARC experts also looked at the cancer-causing potential of betel quid, which is commonly chewed in India and south-east Asia and usually consists of areca nut, betel leaf, catechu, slaked lime, and sometimes tobacco. There is now sufficient evidence that chewing betel quid can cause oesophageal cancer, and limited evidence for an association with liver cancer. It had already been shown that chewing betel quid can cause mouth cancer.

The report finds some evidence that alcohol may cause pancreatic cancer. The existing list of cancers linked to drinking includes cancers of the mouth, pharynx, larynx, oesophagus, bowel, liver and breast. And there's now enough evidence to say that acetaldehyde, a chemical that is produced when alcohol is broken down in the body, can cause cancer. This strengthens the evidence on how alcohol and cancer are linked.

The report also notes that the risk of alcohol-related cancers is particularly high among east Asian populations, many of whom are unable to process it properly because of genetic differences. This leaves them at an increased risk of cancers of the oesophagus, head and neck.

The IARC also looked at the effect of indoor emissions from coal burning on cancer risk. It concluded that in some parts of the world - where coal is regularly used for heating and cooking, often in poorly-ventilated spaces - women and young children who spend more time indoors are particularly at risk.

Jean King, Cancer Research UK's director of tobacco control, said: "Smoking is the single greatest avoidable risk factor for cancer, with the list of cancers caused by tobacco starting at the mouth, moving through and affecting many other parts of the body, including the stomach, pancreas and bladder. This review adds bowel cancer along with a type of ovarian cancer to that list.

"This report also shows just how important it is for parents and expectant parents to quit. Children of parents who smoke may be at greater risk of leukaemia and a type of liver cancer. We hope that more and more parents will ensure that their homes and cars are smokefree.

"Tobacco is a deadly product, and the UK is moving in the right direction of trying to minimise the devastating impact it can have. Ongoing reviews like this highlight the need for other countries to move towards protecting young people and supporting those smokers who are ready to quit."

References

Secretan, B., Straif, K., Baan, R., Grosse, Y., El Ghissassi, F., Bouvard, V., Benbrahim-Tallaa, L., Guha, N., Freeman, C., & Galichet, L. (2009). A review of human carcinogens—Part E: tobacco, areca nut, alcohol, coal smoke, and salted fish The Lancet Oncology, 10 (11), 1033-1034 DOI: 10.1016/S1470-2045(09)70326-2