Yes, no joke at all there. The organophosphates in the oils cause damage, full stop. While there are problems with a few different types of aircraft, the DHLair situation is somewhat different. The airplanes aren't just getting a bit of a background smell anymore, they're regularly flooding the flight deck with intense fumes. There's talk of getting a sniffer system in the cockpits to measure air quality, but that's a complete waste of time, and really just an attempt by the company and the CAA to whitewash this problem. The crews themselves know when the things are full of fumes, the fould smell tells them so!
Also, once this stuff gets into your system it doesn't get out. you have it for a very very long time. I understand decades, if not for life.
google oil fumes and 757s. you'll only find the tip of the iceberg regarding this problem, though.
The bottom line is, if you breath this stuff, and you will, almost nightly if you fly these old 757s (at least a third of the machines pong of the stuff all the time) you will damage your health long-term.