Lead found in and on crops in these highway proximity tests was caused principally by aerial deposition. Substantial amounts of Pb were removed from exposed plant tissues by distilled water washing. Amounts of Pb in and on crops were influenced by distance from the highway, extent of plant surface exposed, external plant characteristics, duration of plant exposure, motor vehicle traffic density, and direction of prevailing winds. In soils and suspended air particulates, concentration of Pb was influenced by distance from highways, and the direction of prevailing winds.

Return to top