The subvention otherwise due a district may be reduced by the state board up to an amount equal to the funds that are granted to the district by the federal government. In so reducing a subvention, the state board shall take into account all of the following factors:

1. (a) The purpose for which the federal funds were granted.
2. (b) The needs of the district in relationship to the needs of other districts.
3. (c) Any special and worthy programs conducted by the district not required by the plan or program approved by the state board pursuant to Section 41500.
4. (d) The severity of air pollution within the district.
5. (e) Any other factors that the state board reasonably determines should be considered.