That depends on exactly what you change them to, and the existing values. For existing values that are integers, there's no loss of accuracy, but for any non-integer value, you can lose considerable precision if the number of decimal places you specify is small enough, and/or the level of accuracy needed is high enough. As an example, if you use a given field to represent an amount of money, and the smallest division of the money amount would result in at most 2 digits to the right of the decimal, AND, you know beyond all doubt that your data conforms, then you can use a SCALE of 2 without a problem. On the other hand, if you need to represent scientific data or measurements of some kind, moving away from float could have serious consequences for statistical measures or other group calculations. Unfortunately, you'll need to review the usage and representation for every field for which you contemplate a change.

Without considerably more detail, we'd have great difficulty providing much more than generalities... which may or may not apply to your situation.