In S06E13, upon returning from a mission with an alien device, Jonas Quinn sees an alien creature that no one else can see. When the entire team is ordered to take some down-time, they discuss the situation and Jonas says the following:
JONAS: You think I'm having symptoms related to my prior exposure to naquadria, like the others on my planet.
Other than S05E21, in which Daniel Jackson received
a lethal dose of radiation poisoning from his exposure to the Naquadria device
I'm not aware of any "symptoms" related to Naquadria exposure.
What symptoms on Langara is Jonas Quinn referring to?