London, Oct 31 : Researchers have for the first time found that phenanthrene -- one of the most common byproducts of the burning of fossil fuels -- causes heart arrhythmias in mice, proving that it is toxic to mammals. Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) that is present in crude oil and is emitted into the air when fossil fuels are burnt. Previous studies have established phenanthrene's toxicity to the hearts of fish and crustaceans. But now researchers from the University of Manchester in the UK have discovered the change also occurs in healthy mouse hearts when directly exposed to phenanthrene, mimicking what happens when humans breathe in pollution. 'We've known that phenanthrene is causally linked to cardiotoxicity in fish for many years ' scientists recognised this following the disastrous impact of the Exxon Valdez oil disaster in Alaska in 1989,' said Professor Holly Shiels from the varsity. 'But we now know this same effect occurs in mammals, and we are also able to show its causal mechanism. It is widely known that PAH's in general are bad for human health, but no one really studied the impact of the lower molecular weight PAH's, Shiels said. In the study, when phenanthrene was applied to an isolated mouse heart, it caused monophasic tachycardia, which is when the heart starts to beat too quickly. Tachycardia is a form of arrhythmia common in people who have scarring caused by a heart attack or past heart disease. The researchers were able isolate single heart muscle cells known as myocytes to understand how electrical dysfunction arrhythmias were achieved. They showed that phenanthrene disrupts the contractile and electrical function of the mouse heart by blocking ion channels required for synchronous beating of the heart. 'Similar effects in humans could have serious health consequences which is why we need greater regulatory attention of this ubiquitous pollutant generated from fossil-fuel combustion,' added lead author Dr Sana Yaar, from the varsity. /IANS