Iowa Code § 330A.16

The effectuation of the authorized purposes of an authority shall be in all respects for the benefit of the people of the state and the member municipalities, for the increase of their commerce and prosperity, and for the improvement of their welfare, health, and living conditions, and since an authority will be performing essential governmental functions in effectuating such purposes, an authority shall not be required to pay any taxes or assessments of any kind or nature whatsoever upon any property required or used by it for such purposes, or any rates, fees, rentals, receipts, or incomes at any time received by it, and the bonds issued by an authority, their transfer and the income therefrom (including any profits made on the sale thereof) shall at all times be free from taxation of any kind by the state, or any political subdivision or taxing agency or instrumentality thereof.