To protect the safety of employees in all hazardous occupations in mining, smelting, manufacturing, railroad or street railway transportation, or any other industry, as provided in section 7, article 18 of the constitution, any employer, whether individual, association or corporation, is liable for the death or injury, caused by an accident due to a condition or conditions of such occupation, of an employee in the service of such employer, in a hazardous occupation, in all cases in which the death or injury of the employee is not caused by the negligence of the employee killed or injured.