If all the nation's vehicles were powered by hydrogen fuel cells rather than fossil fuels, the drop in pollutants that cause asthma, respiratory problems and other potentially life-threatening conditions could reduce deaths by over 6,000 a year. So says a study in Science conducted by Mark Jacobson and colleagues at Stanford University, California1.

"That's a tremendous health benefit," says Jacobson.

The work challenges a common objection to working towards a 'hydrogen economy', in which hydrogen replaces oil as the main fuel source. Many people argue that because hydrogen will probably be generated by burning fossil fuels, a hydrogen system is no better for our planet than oil. Both produce the greenhouse gas carbon dioxide, although at different points in the cycle of fuel production and use.

However, the problem with the internal combustion engine is not just its carbon dioxide emissions. It also produces poisonous carbon monoxide, smog-inducing nitrogen oxides, and ozone, an eye and respiratory irritant. Worst of all, it creates microscopic soot particles that cause a host of health risks and affect climate. Moreover, fossil-fuel vehicles tend to concentrate these pollutants in areas of high population density.

Healthy approach

Focusing on the health issues of hydrogen vehicles might convey their benefits to policy-makers in a better way than more general talk about emissions and pollution, says Ralph Cicerone, president-elect of the US National Academy of Sciences and an atmospheric chemist at the University of California, Irvine. "It's an interesting angle," Cicerone says.

Jacobson and his colleagues considered the effects of replacing all fossil-fuel vehicles in the United States with ones powered by hydrogen fuel cells, which burn hydrogen in air to produce electricity and water. Such vehicles exist already, although not in large numbers.

The team then considered different ways in which the United States might obtain this hydrogen, including extraction from natural gas or coal, or electrolysis of water (which requires electricity, perhaps generated from fossil fuels).

They ran computer simulations to determine the state of the atmosphere for each scenario. They also calculated what it would be like if all vehicles were converted to fossil-fuel/electric hybrids, of which there are various models on the market.

Regardless of the hydrogen or electricity source, air quality improved in all cases. There was less carbon monoxide, ozone, nitrogen oxides and the eye irritant peroxyacetyl nitrate, as well as fewer sooty carbon particles.

Fewer headaches

This would bring substantial health benefits. The incidence of minor ailments such as headaches, sore throats and eye irritation drops by tens of millions a year in all the scenarios. The number of mortalities caused by air-quality problems falls by up to 6,400 a year with hydrogen cars. Hybrids would save fewer lives than that, but would be better for health than today's fossil-fuel burning cars.

Unsurprisingly, Jacobson and colleagues find that the best-case scenario is that in which hydrogen is produced from water using electricity generated by wind turbines.

The problem, however, is determining whether these scenarios are feasible. Producing hydrogen from water through wind power is expensive. And there are problems with storing, transporting and distributing hydrogen fuels.

Still, Jacobson says he hopes that focusing on the health effects will help to make the case for hydrogen and renewable energy. "It's not that nobody cares about these things," he says, "it's just that nobody knows about them."