Salt can come from two sources. The first, and most common, source is road salt. The spray kicked up by passing cars will blow to nearby evergreens. If the injury is slight the plant may just yellow. If the injury is severe the needles may be killed and the branch may not grow.
Road salt can be in run-off from roads and, to a lesser extent, sidewalks.
This type of injury looks different. The lowest branches to show the injury will be on the side of the tree closest to the source of the salt. The injury will move progressively up to higher branches and most often in a spiral pattern. Road salt is less of a problem in the root zone in wet springs because the rain washes it below the roots. Injury is more severe in dry springs.