Dag
Excellent technical perspective on the subject.
From my own perspective it sounds like these fumes are like numerous other odors detectable by the nose including body odors including foul smelling wind.
Somewhat objectionable and difficult to tolerate for long periods of time. However not a degradation on ones health except in repeated extended exposure.
The repeated exposures seem to be more of a maintenance issue (following the manufactures recommendations) with somewhat of a variation between engine models.
This would suggest that crew objections should be aimed at their maintenace departments who in turn should press the airframe manufacturer for easier solutions.