85A.8  Occupational disease defined.
  Occupational diseases shall be only those diseases which arise out of and in the course of the employee’s employment. Such diseases shall have a direct causal connection with the employment and must have followed as a natural incident thereto from injurious exposure occasioned by the nature of the employment. Such disease must be incidental to the character of the business, occupation or process in which the employee was employed and not independent of the employment. Such disease need not have been foreseen or expected but after its contraction it must appear to have had its origin in a risk connected with the employment and to have resulted from that source as an incident and rational consequence. A disease which follows from a hazard to which an employee has or would have been equally exposed outside of said occupation is not compensable as an occupational disease.
[C50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §85A.8]