THE AIR WE BREATHE
NSF-funded project examines the dangers of fog in the Gulf Coast Region

For four days during the winter of 1952, an unusually thick blanket of fog filled the city of London. “The Great Smog” slowed the entire city, filled its buildings with thick fog, and was responsible for the deaths of thousands of people – some with previously existing heart or respiratory conditions. Others were killed by the chemicals present in the fog itself. London’s trademark fog had become far more than a bothersome weather pattern. We don’t think about moments like this when we drive to work or go for a jog in the early morning mist, but researchers at LSU are working to understand how dangerous this weather phenomenon may be for the health of the people living in the Gulf Coast region.

Essentially, fog is a low lying cloud that hugs the ground. It forms at night as the temperature drops and humidity rises and usually dissipates in the morning. LSU professor of chemical engineering Kalliat Valsaraj is concerned with what resides inside the fog that we breathe. The water droplets of fog can pick up chemicals from the ground and what they may release when photo-oxidation, in this case oxidation caused by UV light from the sun, occurs can be surprising. Some compounds, such as naphthalene, can be harmless in some settings but become harmful once oxidized. Now in the sixth year of an NSF-funded project, Valsaraj and other researchers use fog collectors in Baton Rouge and Houston to study water droplets only a few microns in size as the droplets pick up organic compounds introduced to them.

Aside from this project, there is no extensive data on fog water in the Gulf Coast area despite the fact that such regions have fog events for an average of two to three months a year — typically from November through February but occasionally extending as long as April or May. The frequent presence of fog makes it unusual that so little is known about the weather formation’s content — especially considering the health concerns involved.

“Breathing air in a foggy atmosphere can sometimes be bad for you,” says Valsaraj. “For example, pesticides sprayed on the ground vaporize and are picked up and concentrated into the fog.”

While it is difficult to reduce some of the factors that cause fog to become toxic, researchers are trying to uncover the specific ways it can be harmful to humans and make them aware of the problem.

The study has other practical implications as well. Similar techniques have been used in industry to remove chemicals from water by using air bubbles as filters to capture the unwanted chemicals. A process similar to the one fog undergoes creates sea-salt aerosols. These aerosols release reactive chlorine in the marine boundary layer of the atmosphere and are one of the factors responsible for ozone loss. Valsaraj’s research can help us to understand the chemical processes that form the environment around us locally and globally and how it affects our health on a day-to-day basis.

ON THE WEB:
LSU Department of Chemical Engineering

from Summer 2006 Issue