Only through ownpal = 0, but it would have to be dictated by the character's own palfx. If you want it to be independent from the player, use a helper with ownpal = 1 to mimic an explod and apply palfx in it instead.
Its a parameter of both explod and helper. The docs detail any parameter that exists. If you're not sure please take a look there. Far faster than waiting for an answrr here