Does anyone think this toxic tort case would be hard to prove in a court of law?

A company has an employee painting with highly toxic epoxy paint in an enclosed space over a four month period with inadequate ventilation. The employee suffers Acute Liver Failure which requires an emergency transplant. The employee's transplant physician claims the liver injury was caused by a toxin most likely from the job. But he cannot pinpoint the exact toxin. Note: The paint's Material Safety Data Sheet claims that this particular paint can cause kidney and liver damage and must be used in a well ventilated area. Also the employee up until the time of the job had no signs of liver problems based on yearly work-related physicals.