Rush-hour pollution may be more harmful than thought

Turns out, rush-hour commuters may be in for a double whammy of pollution exposure.

The first in-car measurements of exposure to pollutants that cause oxidative stress during rush hour commutes have turned up potentially alarming results. The levels of some forms of harmful particulate matter inside car cabins was found to be twice as high as previously believed.

Most traffic pollution sensors are placed on the ground alongside the road and take continuous samples for a 24-hour period. Exhaust composition, however, changes rapidly enough for drivers to experience different conditions inside their vehicles than these roadside sensors. Long-term sampling also misses nuanced variabilities caused by road congestion and environmental conditions.

To explore what drivers are actually exposed to during rush hour, researchers from Duke University, Emory University and the Georgia Institute of Technology strapped specially designed sampling devices into the passenger seats of cars during morning rush hour commutes in downtown Atlanta.

The devices detected up to twice as much particulate matter as the roadside sensors. The team also found that the pollution contained twice the amount of chemicals that cause oxidative stress, which is thought to be involved in the development of many diseases including respiratory and heart disease, cancer, and some types of neurodegenerative diseases.

"We found that people are likely getting a double whammy of exposure in terms of health during rush-hour commutes," said researcher Michael Bergin. "If these chemicals are as bad for people as many researchers believe, then commuters should seriously be rethinking their driving habits."

For the experiment, researcher Roby Greenwald built a sampling device that draws in air at a similar rate to human lungs to provide detectable levels of pollution. The device was then secured to the passenger seats of more than 30 different cars as they completed more than 60 rush hour commutes.

Some drivers took highway routes while others stuck to busy thoroughfares in downtown Atlanta. While other details like speed and having windows rolled down varied, all of the sampling found more risk in air exposure than previous studies conducted with roadside sampling devices.

Reactive oxygen species found by this study can cause the body to produce chemicals to deal with the reactive oxygen. Particulate matter causes the same response. In combination, the exposure triggers an overreaction that can be destructive to healthy cells and DNA.

Oxidative stress -- the phenomenon antioxidant foods are supposed to address -- is thought to play a role in a wide range of diseases including Asperger's syndrome, ADHD, cancer, Parkinson's disease, Alzheimer's disease, atherosclerosis, heart failure and heart attack, sickle cell disease, autism, infection, chronic fatigue syndrome and depression.

The results are published in the journal Atmospheric Environment.