Lemon juice spruces up not only exhausted humans but car exhausts too, say researchers from the Institute of Catalysis and Petrochemistry in Madrid, Spain. Their report appeared online in Environmental Science and Technology recently.

Catalytic converters of cars that run on diesel become inefficient after the vehicles are driven for about 80,000 kilometres. This is because of deposition of sulphur (present in the diesel) and phosphorus (from anti-wear oil additives in the engine oil) on the platinum honeycomb structures in the catalytic converter. The platinum acts as a catalyst to convert poisonous carbon monoxide and unburnt hydrocarbons into more benign carbon dioxide.

The scientists found citric acid