Even one horse's death is one too many, but not all deaths can be attributed wholely and solely to the track surface.
Many horses come to grief by simply changing stride during running, others get checked by other runners, lose their balance and fall.
The only foolproof way to fully protect racehorses would be to ban horse racing altogether and we all know that this is not an option as the death of a small percentage of horses could not justify the death of an entire industry.