New research has linked air pollution nanoparticles to brain cancer for the first time.
The ultra-fine particles (UFPs) are produced by fuel burning, particularly in diesel vehicles, and higher exposures significantly increase people’s chances of getting the deadly cancer. Previous work has shown that nanoparticles can get into the brain and that they can carry carcinogenic chemicals.
Brain cancers are rare, and the scientists have calculated that an increase in pollution exposure roughly equivalent to moving from a quiet city street to a busy one leads to one extra case of brain cancer for every 100,000 people exposed.
“Environmental risks like air pollution are not large in magnitude – their importance comes because everyone in the population is exposed,” said Scott Weichenthal, at McGill University in Canada, who led the study. “So when you multiply these small risks by lots of people, all of sudden there can be lots of cases. In a large city, it could be a meaningful number, particularly given the fact that these tumours are often fatal.”
The new study, published in the journal Epidemiology, found that a one-year increase in pollution exposure of 10,000 nanoparticles per cubic centimetre – the approximate difference between quiet and busy city streets – increased the risk of brain cancer by more than 10%.
The pollution levels in the cities studied – Toronto and Montreal – ranged from 6,000/cm3 to 97,000/cm3. Weichenthal said people living with pollution of 50,000/cm3 have a 50% higher risk of brain cancer than those living with 15,000/cm3.
Prof Jordi Sunyer, at the Barcelona Institute for Global Health in Spain, who was not involved in the new research, said: “This is an important finding, given that UFPs are directly emitted by combustion cars and several studies in animals have shown UFPs could be more toxic than larger particles.”
Prof Barbara Maher, at the University of Lancaster, UK, said iron-rich nanoparticles from traffic pollution were likely to be carcinogenic and were therefore a plausible possible cause of brain cancer. She said nanoparticles were not regulated and were rarely even measured. Maher said, “We have measured these outside primary schools in the UK, where UFP particle numbers regularly exceed 150,000 per cubic centimetre of playground air.”Toxic air has been linked to other effects on the brain, including huge reductions in intelligence, dementia and mental health problems in both adults and children. The World Health Organization says air pollution is a “silent public health emergency”.