I count seven people (including myself) with no vested interest saying ACS grade is fine and dandy, and one person giving the opposite answer. The lone dissenter sells ACS grade Lugol's, and purifies it into the safest possible product using the twin sciences of marketing and sales. Paying more helps us to avoid worrying over vague threats.
So, add to the list of equivalent or superior products Niles Biological. I got a definitive answer on the formulation of their Lugol's solution. Their chemist uses ACS grade Iodine and potassium iodide. The Lugol's they sell is 5% Iodine and 10% potassium iodide.
The 500 ml (a little more than 16 oz.) bottle is $16.00 plus shipping. The ordering process is easy.