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Cleaner Air Helping London Cathedral

Building shows less weathering

By Robert Preidt
HealthScout Reporter

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SUNDAY, Dec. 3 (HealthScout) -- Lower air pollution levels in London have
cut in half the rate of weathering on St. Paul's Cathedral, one of the
city's most famous landmarks, says a new study.
The stone surface of the balustrade surrounding the upper level of the
cathedral is losing an average of 0.024 millimeters a year, according to
measurements taken repeatedly since 1990. But from 1980 to 1990, the loss
averaged 0.045 millimeters a year.

"The rates have halved, but of course to the general public, going from half
a millimeter in 10 years to a quarter of a millimeter in 10 years doesn't
sound like very much. But we see it as highly significant," says lead
researcher Steve Trudgill, director of studies in the geography department
at the University of Cambridge.

Still, the cathedral is not safe from deterioration, Trudgill says.

"It's still quite high, so we're not complacent," because he says the
deterioration rate at St. Paul's is still higher than rates measured at some
non-urban sites. Results of the study were presented earlier this fall at a
conference of the British Geomorphological Research Group held at the
University of Sheffield.

The decrease in weathering rates is linked to two things: better pollution
control and a decline in heavy industry in and around London, Trudgill says.
Perhaps most significant, he says, was the 1983 closing of the Battersea
Power Station, located in the center of London, which had been a major
source of sulfur dioxide.

Yearly averages of sulfur dioxide concentrations in London's air decreased
from around 25 parts per billion (ppb) in the early 1980s to 10 ppb in the
1990s.

"I think the air, in terms of sulfur, is lower perhaps now than at any time
since the industrial revolution," Trudgill says.

While there's still cause for concern, he says there's also reason to be
pleased with the reduction in pollution-related weathering on buildings
throughout London, with its treasure trove of historic structures.

"It's a good-news story. It's encouraging," Trudgill says.

But just because buildings are getting some relief doesn't necessarily mean
the same is true for the lungs of London's residents, he says.

"The story has got confused sometimes. It's not the same as issues related
to cars or quality of breathing. Street-level pollution is still there," he
says.

An expert on urban air pollution agrees.

"Yes, levels of sulfur dioxide have declined over the last couple of
decades, and, yes, correspondingly the associated health risks have
diminished," says Dr. Raymond Agius, senior lecturer in occupational and
environmental health at the University of Edinburgh in Scotland.

"Particulate pollution has declined, too, but remains a serious health
concern, while oxides of nitrogen concentrations have not fallen much, if at
all," Agius says.

What To Do

For more information on urban air pollution and health, check information
provided by the Berkeley Lab in California.

And for more on how air pollution affects a city's youngest residents, check
the EcoMall.

Or, you might want to read previous HealthScout articles on air pollution.