TUESDAY, March 7, 2017 (HealthDay News) -- A tax designed to reduce mid-city traffic in Stockholm, Sweden, was tied to a reduction in asthma attacks in children, a new study suggests.
"The key takeaways of this paper are that health gains can be realized through efforts to lower air pollution, and that we need to be patient in waiting for the complete picture to emerge," said study author Emilia Simeonova, an assistant professor at Johns Hopkins University in Baltimore.
After Stockholm introduced the "congestion tax" as an experiment in 2006 to discourage people from driving in the center of the city, traffic flow got better and air pollution levels fell by 5 to 10 percent. The tax was made into law in 2007.
The tax costs drivers the U.S. equivalent of $2.60 when they drive in certain areas of the city at congested times of the workday. The tax is collected through scanners that gather license plate information.
In addition to the drop in air pollution levels, there was an unexpected drop in childhood asthma rates for kids up to 6 years old. Asthma attacks declined nearly 50 percent among local children after the introduction of the tax, according to the study findings.
However, the study couldn't prove a direct cause-and-effect link.
The researchers reported the decrease in asthma attacks occurred gradually, over several years.
Asthma attacks fell more than 12 percent in the first seven months after the congestion tax was introduced. Over the next few years, asthma declined 47 percent, the study found.
That suggests the full benefits of reduced air pollution might not occur immediately, according to Simeonova.
"These findings show that traffic congestion fees in large cities can have significantly positive effects on health in the short term but even larger effects in the longer term," Simeonova said a Hopkins news release.
The study was presented at the annual meeting of the American Economic Association, in Chicago. Findings presented at meetings are generally viewed as preliminary until they've been published in a peer-reviewed journal.
The U.S. National Heart, Lung, and Blood Institute has more on asthma.