What do socked or barefooted passengers leave behind? 10News used petri dishes to gather samples where passengers picked up their carry-ons off the conveyer belt at the security checkpoint.

After sampling in San Diego, a 10News employee headed to Las Vegas and Phoenix -- two popular destinations for San Diegans.

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The lab identified a mold from McCarron Airport in Las Vegas as trichophyston, which causes ringworm and favus, a nasty disease of the scalp.

The next test was from Sky Harbor Airport in Phoenix, where samples were lifted to test for bacteria.

Scientists found bacteria and fungus unique to the areas where passengers removed their shoes.