Following a ban on smoking in casinos in Gilpin County, Colo., ambulance calls dropped by 20 percent, a new study reveals.

The data comes as 36 of the 50 U.S. states have enacted some form of official smoking ban, although many casinos still remain exempt from these bans. In 2008, Colorado decided to join the 36 and remove the exemption altogether, prompting researchers to analyze the data on ambulance calls within Gilpin County — the county with the densest collection of casinos, boasting 26 in three square miles.

The researchers relied on previous data from just after a 2006 ban, which prohibited smoking in all indoor areas except casinos. Following that ban, ambulance calls dropped by 22.8 percent.

Led by University of California, San Francisco professor, Dr. Stanton A. Glantz, the most recent study compiled data from January 2000 to December 2011 in order to track ambulance calls as they related to the 2008 ban.

The greatest effects, surprisingly, may not be coming from the smokers themselves, but from the non-smokers who breathe in the secondhand smoke.

"Inhaling secondhand smoke increases the chances of blood clots that can block arteries and makes it more difficult for arteries to expand properly, changes that can trigger heart attacks," said Glantz, who has been studying the effects of secondhand smoke on the lungs and heart for decades.

Oftentimes, casinos resist the ban, citing a majority of their clientele as smokers who the casino would prefer keep smoking while gambling.

"It's politics," Glantz, whose most recent study showed a 19-percent drop in ambulance calls, told NPR. "Tobacco and gaming interests really fight for these exemptions."

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The drop is not a causal link, despite how strong the correlation may seem. Other reasons for the decline could be that due to depressed economic times, fewer people are gambling, and that higher gas prices have dissuaded people from driving to the casinos.

"The calls may also have decreased due to smokers not being able to smoke in the casinos," said Glantz, who also works as director of the Center for Tobacco Control Research and Education, "thus avoiding the immediate toxic effects of smoke on their blood and blood vessels, and because some people quit smoking."

He cites the two dips in ambulance calls, in 2006 and 2008, as clear evidence that smoking puts unnecessary strain on the emergency response systems, insurance, and welfare programs. Smoking currently ranks first on the list of preventable causes of death in the United States.

"Casinos are often exempted from legislation mandating smoke-free environments, putting employees and patrons at risk for heart attacks, strokes, asthma attacks, and other adverse events triggered by secondhand smoke," Glantz added. "The message to policymakers is clear: Stop granting casino exemptions. They lead to a substantial number of people being sent to the hospital, often at taxpayer expense, something that is completely preventable."