edit to add: These spacecraft all use very toxic fuels, and this one has had issues with fuel leaks before [0]. I'm not sure how or if those could affect the crew. Maybe if there was contamination on an exterior surface, they could have been exposed on landing? IIRC it is or used to be standard procedure to take air samples before opening crewed spacecraft, for this reason.
edited again to add: I found it! It Apollo-Soyuz in 1975—the entire Apollo crew were poisoned by fuel when they opened the spacecraft, and were hospitalized with chemical pneumonitis [1,2].
[0] https://arstechnica.com/science/2022/06/nasa-delays-cargo-dr... ("NASA and SpaceX stand down on Dragon launch to study hydrazine issue")
[1] https://en.wikipedia.org/wiki/Apollo–Soyuz#Re-entry_and_afte...
[2] https://ntrs.nasa.gov/citations/19770023791 ("The Apollo-Soyuz Test Project: Medical report")
- (wiki) "The only serious problem was during reentry and splashdown of the Apollo craft, during which the crew were accidentally exposed to toxic monomethylhydrazine and nitrogen tetroxide fumes, caused by unignited reaction control system (RCS) hypergolic propellants venting from the spacecraft and reentering a cabin air intake. The RCS was inadvertently left on during descent, and the toxic fumes were sucked into the spacecraft as it drew in outside air. Brand briefly lost consciousness, while Stafford retrieved emergency oxygen masks, put one on Brand, and gave one to Slayton. The three astronauts were hospitalized for two weeks in Honolulu, Hawaii.[22] Brand took responsibility for the mishap; because of high noise levels in the cabin during reentry, he believed he was unable to hear Stafford call off one item of the reentry checklist, the closure of two switches which would have automatically shut off the RCS and begun drogue parachute deployment. These procedures were manually performed later than usual, allowing the ingestion of the propellant fumes through the ventilation system.[23]"