Unproven cancer risks diverting focus from real cause: lifestyle

The risk of cancer from air pollution is a fraction of the hazard posed by smoking. EPA/Alex Hofford

The fixation on potentially cancer-causing chemicals in the air, food and consumer products is diverting attention from the real risks, according to a review of global evidence by an Australian cancer researcher.

Writing in the medical journal The Lancet Oncology, Professor Bernard Stewart, from the University of New South Wales, said that lifestyle factors - driven by “personal choices” - were the most significant proven causes of cancer.

“Measures known to prevent cancer include smoking cessation, reducing alcohol intake, curbing obesity and avoiding deliberate sun exposure,” said Professor Stewart, who reviewed medical literature from around the world on known and suspected cancer hazards.

“Diverting attention from these messages threatens to undermine their efficacy to deliver proven benefits.”

Alarmist media reporting had heightened fears about a multitude of possible cancer causes - from widespread and localised pollution, to pesticides, endocrine disrupting chemicals and consumer products such as mobile phones, he said.

Air pollution was the only environmental factor that had conclusively been shown to increase the risk of cancer: The European Prospective Investigation into Cancer and Nutrition found that in one population, the proportion of lung cancers attributable to air pollution was 5-10%.

But the risk was “at least 10 times less than it is for smoking”, Professor Stewart said.

Alcohol, smoking and obesity are among the major causes of cancer. EPA/Alex Hoerhager

Of 32 pesticides reviewed in 2010 for carcinogenic risk, none could be clearly implicated, but some were recommended for further investigation.

Professor Stewart’s report also noted that occupational studies had “not implicated any chemical class as accounting for pollution-associated risk of breast cancer”.

Though exposure to very small amounts of carcinogenic chemicals occurred as a result of food contamination and by using certain consumer products, these circumstances had never been shown to cause cancer in developed countries, he said.

“Cancer has not been shown to have arisen because regulatory authorities overseeing food standards or consumer product safety overlooked the evidence, with the possible exception of quicker action to ban tanning devices.”

Ian Musgrave, a senior lecturer in Pharmacology at University of Adelaide, said the report was a timely reminder that regulatory bodies needed to think carefully about how they allocated limited resources to preventative measures.

“I’m not saying that environmental pollution is not important,” he said. “But people are focusing on the smallest impact with the least evidence rather than those with high impact and the most evidence.”

It would be more useful to contemplate the hazards over which they had immediate control: “We can choose to stop smoking, control our food intake and consume less alcohol.”

Angela Casauay contributed to this report.