Massachusetts’ ban on workplace smoking has helped lower the number of people exposed to cancer-causing smoke on the job, but employees in lower-paid positions are significantly less likely to be protected, according to a study being released Monday.
The findings reveal that just 3 percent of nonsmokers in professional fields, such as software engineers, architects, teachers, doctors, and nurses, reported being exposed to a co-worker’s tobacco smoke. In contrast, 37 percent of trade workers who didn’t smoke, including auto body workers, locksmiths, cable TV installers, and heating and air conditioning mechanics, said a colleague lit up in their presence on the job.
Many other nonsmoking, blue-collar employees also reported high rates of exposure to secondhand smoke, including 23 percent of construction workers and 20 percent of transportation workers, such as taxi drivers, bus drivers, and parking lot attendants.
“Workers in these occupational groups may be in environments not covered by the workplace law, or they work in places where the law does apply but it’s difficult to enforce, like in vehicles,” said Kathleen Fitzsimmons, a disease tracker with the Massachusetts Department of Public Health, and lead author of the study.
The law, passed in 2004, prohibits smoking in all enclosed workplaces. If more than one employee uses a company vehicle, that vehicle is covered under the law, and smoking is prohibited. The law includes taxis, delivery vans, and municipal vehicles, but not private cars.
Massachusetts was the third state, behind Delaware and New York, to enact a Smoke-Free Workplace Law. There is no level of exposure to secondhand smoke that is considered safe, according to a landmark 2006 US Surgeon General’s report, which concluded that such smoke causes lung cancer and heart disease, and can exacerbate respiratory diseases such as asthma.
The researchers, who are slated to present their findings Monday at the American Public Health Association’s annual conference in Boston, analyzed data from surveys of more than 6,000 Massachusetts workers between 2003 and 2010.
The annual, random telephone surveys asked respondents whether they smoked and also whether they were exposed to other people’s tobacco smoke while at work.
The year before the law went into effect, 8 percent of nonsmokers said they were exposed to a colleague’s tobacco smoke, according to the study. In 2010, the most recent year for which data are available, that rate had dropped to 5.4 percent.
At the same time, smoking among Massachusetts workers declined from 18.5 percent in 2004 to 12.7 percent in 2010.
Fitzsimmons said smoking rates had been declining before the law was passed, but the drop was steeper after it went into effect.
“Our findings suggest that comprehensive smoking bans work,” Fitzsimmons said. “But our results reveal there is more work to be done.”
Taken together, workers in the three occupational groups most likely to face secondhand smoke on the job — installation and repair, construction, and transportation — accounted for just less than 12 percent of the Massachusetts workforce in 2010, the study found.
The new findings suggest that certain groups may be facing a “double jeopardy” in health risks, said Glorian Sorensen, a social and behavioral sciences professor at the Harvard School of Public Health who studies smoking in the workforce.
“Many of these workers have other exposures on the job” in addition to secondhand smoke, she said. “If you are a stonemason, you are exposed to silica, so you already have a respiratory hazard on your work.”
Similarly, truck drivers are probably also exposed to diesel exhaust, said Sorensen, who has studied smoking among truckers.
“If you are driving with a smoker, you are going to be exposed,” she said. “There is less capability in that work environment to enforce these regulations.”
Sorensen said the enormous disparities among workers exposed to secondhand smoke highlight the need for better enforcement of workplace smoking bans.
“For these workers,” she said, “we need to provide a safer and healthy work environment.”
Municipal health inspectors are generally the authorities who enforce the law, typically by responding to complaints from workers.
Patti Henley, director of the state health department’s office of community health and chronic disease prevention, said the study’s findings should help local inspectors better target their surveillance and education outreach to workplaces where smoking violations have been found to be more prevalent.Kay Lazar can be reached at email@example.com. Follow her on Twitter @GlobeKayLazar.