Air pollution levels from secondhand smoke in some casinos are so high that less than two hours of exposure could put nonsmoking casino patrons and workers at acute risk of heart disease, a new study says.

Smoke-free casinos in the U.S. are rare, with 88 percent of commercial casinos and all tribal casinos allowing smoking. The new report by scientists at Stanford and Tufts universities, published in the journal Environmental Research, indicates the toll that secondhand smoke in casinos is taking — even in casinos providing nonsmoking areas and using ventilation and air cleaning systems to control smoke levels.

“Casino patrons are gambling not only with their money, but with their health, and the odds are stacked against them,” Lynn Hildemann, a Stanford engineering professor and the principal investigator for the study, told Stanford University News.

The researchers measured particles from secondhand smoke inside and outside eight casinos in the Reno, Nev., area, and combined that data with previous studies, to evaluate a total of 66 U.S. casinos. Particles in about half the casinos exceeded a level known to impair the heart’s ability to pump blood after less than two hours of exposure, “posing acute health risks to patrons and workers,” the study says.

Air pollution levels exceeded World Health Organization standards in 93 percent of the smoking casinos, according to the report. Nonsmoking restaurants in casinos with no structural separation from gaming areas also showed “quite high” levels of particulates.

“Creating nonsmoking areas isn’t offering very much protection,” Hildemann told the Reno Gazette-Journal.

An official at the Silver Legacy casino in Reno touted its air filtration system. “We have two major venting systems that move air, so much so that you can stand outside the cafe or Brew Brothers and feel your pant legs moving, you can feel the air moving,” General Manager Gary Carano said.

But Hildemann said that the only effective control for secondhand smoke is reducing the number of smokers. “The fewer smokers, the less polluted the air,” she said.