Any poisonous or deleterious substance added to any food, except if it is required in the production of the food or cannot be avoided by good manufacturing practice, shall be deemed to be unsafe for purposes of subdivision 2 of § 3.2-5122; but when any poisonous or deleterious substance is required or cannot be avoided, the Board shall adopt regulations limiting the quantity to such extent as it finds necessary for the protection of public health. Any quantity exceeding the limits established by the Board shall also be deemed to be unsafe for purposes of the application of subdivision 2 of § 3.2-5122. While such regulation is in effect limiting the quantity of any poisonous or deleterious substance in any food, such food shall not, by reason of bearing or containing any added amount of such substance, be considered to be adulterated within the meaning of subdivision 1 of § 3.2-5122 if the added amount is not in excess of the limits established by the Board. In determining the quantity of any added substance to be tolerated in or on different articles of food, the Board shall take into account the extent to which the use of such substance is required or cannot be avoided in the production of each article, and the other ways in which the consumer may be affected by the same or other poisonous or deleterious substances.