3-nitrobenzanthrone, had the highest ever score on a standard test for cancer-causing potential of toxic chemicals. It also caused chromosomal aberrations in the blood cells of mice. "I personally believe that the recent increase in the number of lung cancer patients in vehicle-congested areas is closely linked with respirable carcinogens such as 3-nitrobenzanthrone," said Hitomi Suzuki, a chemist at Kyoto University, who conducted the study. When Suzuki tested the compound on a strain of salmonella he found that if caused more mutations than 1.6 dinitropyrene, the previous most powerful known mutagen. Although both compounds are found only in minute quantites, they are so dangerous that "it is easily understandable that they would contribute considerably to the total mutagenic activity of diesel exhaust particle extracts", Suzuki added. He called for stronger limits on the loads that diesel trucks can carry because there are more emissions from engines under heavier loads.