In order to comply with EPA (Environmental Protection Agency) regulations, and at a cost of about $5.2 million per ICBM, the rocket motors on 500 Minuteman III missiles will be replaced with new ones. These rockets will emit less toxic chemicals when used.
[…]
Thus, if the Minuteman III ICBMs have to be used in some future nuclear war, their rocket motors will not pollute the atmosphere.
(Strategy Page)

See? They _do_ care for the environment