Tom Kasmer , a 14-year-old from Belmont , N.C. , got a word that sounded like " zistee " during yesterday 's competition .
The 14-year-old national spelling finalist who attends school in Belmont , N.C. , got a word that sounded like " zistee " during competition Wednesday .
He said it was not possible to rule out that the chemical was a cancer risk to humans .