Lung hot spots concentrate carcinogensComputer model highlights
cells at cancer risk.
Certain spots in the lungs may accumulate massively more cancer-causing airborne particles than was previously thought, according to a new model1. It suggests that some safe limits for pollutants could be underestimates. Cells on the spurs between airways build up inhaled carcinogens to concentrations at least 100 times higher than elsewhere in the lung, says Thomas Heistracher of the Polytechnical University of Salzburg, Austria. Heistracher and his colleagues used a computer model to simulate the breathing lung - and the hundreds of millions of dust, smoke and other particles that are sucked in and out with each breath. Some current pollution regulations ignore local lung buildups that could spawn cancer, says team member, Werner Hofmann of the University of Salzburg. "It means you should reduce your [allowable] concentrations," he says. But the modeling method needs to be confirmed with further experiments before regulatory agencies - such as the US Environmental Protection Agency - take it into account says Michael Oldham, who studies lung pollution at the University of California at Irvine. "[The method] is still relatively new," he explains. Heistracher's team is one of several that are developing simulations of airflow during breathing, using a technology also employed in aircraft design. "It gives precise predictions of where particles will land in 3D space," says Oldham. The work supports the long-held idea that that forks in the lung catch crud. Before computer models, researchers puffed fumes into plastic or rubber lungs and watched debris collect.
But exactly how these hotspots harm lung tissue is unclear. Some particles are washed away by mucus and coughing; others - such as tobacco smoke - are not, hence the dry, hacking cough of a smoker. Other factors - such as how a pollutant is inhaled - also affect its distribution, points out Naiyer Rizvi, who works on lung cancer at the Memorial Sloan-Kettering Cancer Center in New York. High-tar cigarettes leave deposits high up in the lungs, lower-tar ones stain deeper in the lungs because smokers suck on them harder. Some studies have found a correlation between the sites of lung cancer and the pollutant hotspots. But Rizvi points out that a tumour's origin can be tough to pin down, as tumours often reach several centimetres in diameter before they are found. "I don't think there's a magic spot you can look for," he says. |
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© Nature News Service / Macmillan Magazines Ltd 2003 |
