Sydney, March 30 (IANS) Cigarette filters may have traces of pig's blood, an Australian professor has said, adding the devout may find this "very offensive".

Simon Chapman, a professor at the University of Sydney, said a recent Dutch research had identified 185 industrial uses of a pig - including the use of haemoglobin in cigarette filters.

"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," Chapman was qouted as saying by Australian AAP news agency.

"The Jewish community certainly takes these matters extremely seriously and the Islamic community certainly do as well, as (so) 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."

The research found pig haemoglobin was being used to make cigarette filters more effective in blocking harmful chemicals before it entered a smoker's lungs.

The professor said that one cigarette brand sold in Greece was confirmed to be using pig haemoglobin in its processes, Chapman said.