Welder here. Aluminum oxide inhalation is correlated with an increased risk for alzheimers, not cancer. Hexavalent chromium is a carcinogen, and that comes from heating up stainless steels. So you are actively replacing a relatively non toxic oxide with the potential for an actually toxic carcinogenic gaseous metal, assuming your pocket knife is some sort of stainless steel (statistically very likely).
Welder here. Aluminum oxide inhalation is correlated with an increased risk for alzheimers, not cancer. Hexavalent chromium is a carcinogen, and that comes from heating up stainless steels. So you are actively replacing a relatively non toxic oxide with the potential for an actually toxic carcinogenic gaseous metal, assuming your pocket knife is some sort of stainless steel (statistically very likely).