As per the BBC story (link below) Unite, the union, are claiming pilots and cabin crew are regularly exposed to toxic fumes during flights. (I am not sure how passengers are not exposed?! Maybe it’s the prolonged continuous periods)
The Unite union said legal notice has been served in 51 cases, the majority of which are against British Airways.
British Airways responded that "none of the substantial research conducted over many years" had shown a link between cabin air quality and ill-health.
https://www.bbc.co.uk/news/business-47740523