BOSTON — The nation's largest cigarette maker is disputing a study by the Massachusetts Department of Public Health that found nicotine in cigarettes has risen about 10 percent in the past six years.

Philip Morris USA, which manufactures Marlboro cigarettes, said its review of nine years of data that it provided to the state found fluctuations in nicotine levels, but no steady increase.

"There are variations in the nicotine yield for different Marlboro packings, both up and down from year-to-year, but there is no general trend up or down,"the company, a unit of Altria Group Inc., said in a written response late last week.

The health department study released last month examined nicotine levels in more than 100 brands over a six-year period. The study showed a steady climb in the amount of nicotine delivered to the lungs of smokers regardless of brand, with overall nicotine yields increasing by about 10 percent, according to state health officials.

The study also found the three most popular cigarette brands with young smokers _ Marlboro, Newport and Camel _ delivered significantly more nicotine than they did years ago.

Massachusetts is one of three states to require tobacco companies to submit information about nicotine testing according to its specifications and the only state with data going back to 1997.

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Philip Morris said when it looked at all the data they sent to the state there were only year-to-year variations that"occur as part of the normal processes of growing tobacco and manufacturing cigarettes."

Donna Rheaume, a spokeswoman for the Department of Public Health, defended the report, which concluded that the higher nicotine levels made it easier to get hooked on cigarettes and harder to quit.

"We stand by our study which was based on data supplied by the tobacco companies,"Rheaume said.

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