It’s one of the stranger approaches to reducing air pollution, but it just might work.
Transport for London, the city’s municipal transportation agency, has announced a new $310,000 trial of a "pollution glue" that will be sprayed on 15 separate stretches of road in areas with especially bad air quality and, in theory, trap certain pollutants so that they don’t float around and into people’s lungs.
The so-called "glue" (more formally known as a dust suppressant) is a non-toxic, biodegradable saline solution with calcium magnesium acetate. It will be sprayed on the street at night by winter service trucks modified with sprinklers. Harmful particles stick to the glue, preventing, as Mayor Boris Johnson put it, "their dastardly escape back into the air we breathe." Eventually the particles are washed away into drains or tracked away by traffic.
The dust suppressant isn’t made to trap gaseous pollutants like carbon monoxide but rather small particulate matter that’s produced by diesel vehicles and industrial processes and is especially bad to breathe. The aim is more to improve air quality and public health than combat climate change.
This suppressant has already been tested on a small scale. In November, TfL started applying it in two locations in central London: Marylebone Road and the Victoria Embankment. The city’s studies showed it reduced PM-10 (that’s particulate matter with a diameter of 10 micrometers or smaller) by 10 to 14 percent.
In this expansion of the trial, the suppressant will be used at 15 sites in five London boroughs, all of which are near industrial facilities that produce a lot of air-fouling particles.
Part of the reason London is getting so creative (read: desperate) in its approach to air pollution is that the city’s air quality is still pretty bad and, if the situation doesn’t improve, it could face large fines for violating European Union PM-10 limits.
The dust suppressant scheme isn’t without its critics. Alan Andrews, from the environmental law group Client Earth, says suppressants "address the symptoms and not the causes of the problem." That’s true, of course, but a short-term solution like this can help while longer-term solutions (like the city’s new ban on diesel vehicles) are taking effect.
And if this works, it could be used in other cities in need of whatever short-term air quality fix they can find. Beijing, are you listening?