POLLUTION RISK TO SEA AIR

Dirty smoke pouring out of the funnels of ships at sea or in port is having a major impact on the air quality of coastal cities, a study has found.

Researchers used a chemical fingerprinting technique to identify "primary sulphate" in ship emissions. This consists of tiny sulphur particles, less than 1.5 microns across, which can be carried long distances on the wind. Breathed in, they lodge deep inside the lungs and pose a serious health hazard.

It is estimated that ship pollution may be responsible for as many as 60,000 deaths a year worldwide.

The US scientists from the University of California at San Diego (UCSD) found that ships contributed far more of the sulphate in the atmosphere than was previously realised.

Their analysis separated primary sulphate from ship smoke and other sources, such as vehicle exhaust emissions. Air samples showed that 44% of the sulphate polluting coastal California could be traced to ships.

On some days ship sulphate accounted for almost a half of the fine particles in the air. Ships burning high sulphur fuel in the ports of Los Angeles, Long Beach and San Diego were largely to blame, the scientists discovered.

From July next year, all tankers, cargo and cruise ships sailing into Californian ports will have to switch to more expensive, cleaner fuels when they come within 24 miles of the coast. Similar international rules are due to take effect in 2015.

The research was published in the journal Proceedings of the National Academy of Sciences.

Professor Mark Thiemens, who led the scientists, said: "This is the first study that shows the contribution of ships to fine particulates in the atmosphere. Ships are really unregulated when it comes to air pollution standards. What we wanted to find out was the contribution of ships to the air pollution in San Diego. And what we found was a surprise, because no one expected that the contribution from ships of solid sulphur-rich particles, called primary sulphate, would be so high."