According to Eric Johnson, a scientist at Swiss-based agency Atlantic Consulting, a shift to LPG from diesel would cut particulate emissions by 7%.
Johnson's report, published in the journal Impact Assessment and Project Appraisal, looked at the Government's UK Air Quality Strategy and its goal of cutting particle emissions.
In his report, Johnson concluded: 'One aim of the UK Government's Air Quality Strategy is to reduce emissions of particles. To this end, one policy option currently under consideration is to encourage diesel light duty vehicles to be sold with factory equipped particle traps.
However, there is a better option that is more immediate, lower cost and more effective – switching to LPG-fuelled vehicles.'
Johnson added that if such a move was made, by 2010 vehicle owners could be saving between £173 to £406 per year in expenses and particulate emissions in the UK could be cut by 2% to 7%, or 125 to 538 tonnes. It must be noted, though, that Johnson's calculations are worked out on the hypothesis that by 2010 LPG-powered cars will cost the same as petrol-powered versions, when currently there is about a £2,000 premium before grants. Figures were worked out assuming an annual mileage of 9,866 and an LPG fuel cost of 37.1 pence per litre.
Johnson said: 'A key aim of the Government's air quality strategy is the reduction of particulates. Road transport, primarily diesel engines, is the largest emitter in populated areas, where airborne particulates do the most damage.
'There is currently a debate surrounding the formation of the smallest particulates with evidence that many of these are actually formed post-emission.'
The research has buoyed the LPG industry, which has been concerned that the Government will bring taxation on the fuel closer to that of petrol or diesel.
Calor's Andrew Ford said: 'To focus solely on CO2 ignores the Government's targets on air quality, which aim to address pollutants, including particulates. As Fleet NewsNet has pointed out recently, to pull the rug away at this moment would penalise fleet managers and bode ill for the development of other environmental fuel options.'
However, Citroen, which fits particulate traps to many of its HDi diesel cars, defended their use. A spokesman said: 'Under certain circumstances the emissions from the exhausts of vehicles equipped with particulate filters are actually cleaner than the air taken into the engine in the first place, a clear indication of how clean Citroen's latest diesels are.'