Table 1: Transition probabilities among four health states.

State Baseline Contamination 1 Contamination 2 Failure Baseline 0.9056 0.0879 0.0063 0.0002 Contamination 1 0 0.8491 0.1506 0.0003 Contamination 2 0 0 0.9129 0.0871 Failure 0 0 0 1