Illegally obtained marijuana often contains a common fungus which can cause lung infections and allergic reactions, a researcher at the Milwaukee County General Hospital said in a report published last week.

Dr. Steven L. Kagan said that in recent tests he had found Aspergillus fumigatus in 11 out of 12 marijuana cigarettes and evidence of the fungus in the blood of 11 out of 21 marijuana smokers.

"One has to assume that all street marijuana is contaminated with a number of fungi and molds that can be inhaled by the user," Kagan said in Milwaukee last week, adding that illegal marijuana is "a significant health hazard."

Cancer patients can legally obtain purified marijuana to lessen the nausea and vomiting often caused by chemotherapy and avoid the dangers Kagan described. But patients in pain often seek the drug elsewhere and "must assume special risks" because their immune system has been weakened by other drugs, Kagan said.

Researchers have in the past associated Aspergillus with moldy marijuana, but have never proved that it could be inhaled.

Kagan, who announced his findings in a letter to the editor published in last week's New England Journal of Medicine, used a machine adapted to "smoke" a lit marijuana cigarette to test the fungus content in various marijuana samples.

"The fungus came straight through, unimpeded, which proves that it can implant itself deeply into the lungs," Kagan said.

The researcher also found antibodies produced by the body to combat the fungus in the blood stream of more than half of his subjects.

Water filters used by smokers to remove impure substances from marijuana probably do not remove Aspergillus because the fungus "loves damp areas," Kagan said.

He added that the fungus has not been found in tobacco cigarettes.