No person shall discard any litter onto or in any water or land, except that nothing in this section shall be construed to affect the authorized collection and discarding of such litter in or on areas or receptacles provided for such purpose. When litter is discarded from a motor vehicle, the driver of the motor vehicle shall be responsible for the act in any case where doubt exists as to which occupant of the motor vehicle actually discarded the litter.
(Code of Iowa, Sec. 455B.363)