The Dutchman leaves just over a week after he was caught-up in contoversy the day before the Grand Départ in Utrecht, returning a low-cortisol level in a pre-race test the afternoon prior to the opening time trial.
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Under the rules of voluntary group the Movement for Credible Cycling, of which Astana are members, Boom should have been left out of the Tour because of the test results.
The Kazakh team decided to forego the rules of the MPCC and started with Boom included in its nine-man squad to support Vincenzo Nibali.
Astana were subsequently temprarily suspended by the MPCC over the incident, but have now been forced to pull the rider from the race anyway after suffering illness for the past two days.
It means that Nibali’s squad is the second of the five big favourites’ teams to lose a rider, with Alberto Contador (Tinkoff-Saxo) now riding with seven others after teammate Ivan Basso was diagnosed with testicular cancer on the morning of the first rest day.
Chris Froome (Team Sky), Tejay van Garderen (BMC) and Nairo Quintana (Movistar) all head into the first mountain stage in the Pyrenees with a full complement of team members, as Froome continues to lead the Tour by a mere 12 seconds over van Garderen.
Preview the Tour de France in the Pyrenees