Traces of pig's blood could be included in some cigarettes, warns an Australian academic. He also cautions that religious groups would find its hidden presence "very offensive".
Simon Chapman, a Professor in public health in the University of Sydney, noted a stream of Dutch research which has found 185 different industrial uses of pig parts. One use was found to be pig haemoglobin included in some cigarette filters.
The research provides an insight into the manufacturing of cigarettes, says Professor Chapman, a business that is otherwise very secretive. He also said that this information will likely alarm devout Jews and Muslims.
Both these faiths explicitly ban the consumption of any part of a pig, the rule being a core part of their religion.
"I think that there would be some particularly devout groups who would find the idea that there were pig products in cigarettes to be very offensive," Prof Chapman said on Tuesday.
"If you're a smoker and you're of Islamic or Jewish faith then you'd probably would want to know and there is no way of finding out,"
"The Jewish community certainly takes these matters extremely seriously and the Islamic community certainly do as well, as would many vegetarians. It just puts into hard relief the problem that the tobacco industry is not required to declare the ingredients of cigarettes ... they say 'that's our business' and a trade secret."
Adding pig haemoglobin can make cigarette filters more effective by helping stop some of the dangerous chemicals entering a smoker's bodies, according to the Netherlands study.
Tobacco companies do sometimes list the ingredients in their products on their websites, however, Professor Chapman points to undisclosed "processing aids ... that are not significantly present in, and do not functionally affect, the finished product".
Prof Chapman said that many chemicals and other substances that are used to make tobacco products have been hidden by this simple term.
It has been confirmed that at least one cigarette company in Greece is using pig blood in its products, said Professor Chapman, and the whereabouts of the cigarettes is unknown.
A spokeswoman for British American Tobacco Australia has said that a comment will be provided although it was not available immediately.