'Marlboro Lights' are a thing of the past, but researchers say 'Marlboro Golds' convey the same message. Reuters

Tobacco companies reportedly knew that cigarette smoke contained radioactive alpha particles five years earlier than previously thought and developed a deep and intimate knowledge of the chemicals' cancer-causing potential, according to a new study published in the journal Nicotine & Tobacco Research.

Researchers from the University of California at Los Angeles analyzed dozens of previously unexamined internal documents from the tobacco industry, made available as the result of a legal settlement in 1998, that revealed tobacco companies began in-depth investigations into the possible effects of radioactivity on cigarette smokers as early in the 1960s after becoming concerned about the potential lung cancer risk that could result.

Furthermore, the industry was not only cognizant of the potential 'cancerous growth' in the lungs of regular smokers, but also did quantitative radiobiological calculations to estimate the long-term lung radiation absorption dose of ionizing alpha particles emitted from cigarette smoke, wrote the study authors.

Substance Polonium-210

The radioactive substance was identified in 1964 as the isotope polonium-210, which emits carcinogenic alpha radiation. Polonium-210 can be found in a variety of cigarette brands and is absorbed by tobacco leaves through naturally occurring randon gas in the atmosphere, as well as through high-phosphate chemical fertilizers used by many tobacco farmers.

UCLA researchers report that the Big Tobacco study that was analyzed outlined the industry's growing concern that the inhalation of polonium-210 could pose a cancer risk. Despite their concerns, tobacco companies declined to adopt a technique discovered in 1959 -- and then another one discovered in 1980 -- that could have decreased polonium-210 levels from tobacco. The 1980 technique, known as acid-wash, was discovered to be effective in removing the substance from tobacco plants.

Would An Acid-Wash Have Reduced Nicotine's Addiction Agent?

However, documents show that industry officials were concerned about the cost and potential environmental impact of using the acid-wash. Still, researchers said that profits were likely the real reason companies did not adopt the new method.

The industry was concerned that the acid media would ionize the nicotine, making it more difficult to be absorbed into the brains of smokers and depriving them of that instant nicotine rush that fuels their addiction, Hrayr S. Karagueuzian, the study's first author, said in a statement.

Although the June 2009 passage of the Family Smoking Prevention and Tobacco Control Act grants the U.S. Food and Drug Administration the authority to regulate and remove harmful substances -- except nicotine -- from tobacco products. Karagueuzian said the analysis' findings make a strong case for the FDA to consider making the removal of alpha particles from tobacco a high priority.

Such a move could have a considerable public health impact, due to the public's graphic perception of radiation hazards, he said.