Yes, he certainly could be poisoned if exposed.
Since most effects are either neurological or GI, this can account for his symptoms, particularly if he is very sick and has no fever along with it.
He should be examined at this point.
Even if by an urgent care doctor.
There will not be anything specific to antidote the poisoning, but renal function, liver function, neurological function, and blood levels can be checked.
I would also call poison control to have them check their normograms for these substances against his height and weight.
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