Epidemiologic studies of diseases in which a necessary cause is known

Using process control concepts to model conditions required for sudden-onset occupational injuries

Sudden-onset injury results from a momentary energy exchange between an agent and host, producing immediately discernible tissue damage. These injuries are common in both occupational and nonoccupational settings; typical causes include falls, mechanical contact/crushing, exposure to temperature extremes, and exposure to electrical current. We review epidemiologic and engineering approaches to injury prevention and propose a process control model for describing risk-of-exposure to injury agents during the Pre-event phase of sudden-onset injury. Process control is a proactive approach to quality engineering that is based on the premise of preventing defective products from being manufactured in the first place, instead of relying on reactive inspections to detect defects at the end of the manufacturing process. Principles of process control can be applied by occupational health and safety professionals to prevent workplace injury. The proposed model describes how work activities (process inputs) cause risk-of-exposure to injury agents to fluctuate over the course of a work shift. Risk-of-exposure is a complex function with many input factors including: the nature/magnitude of hazards, the presence and effectiveness of engineering controls, safety climate, management attitudes and practices, the surrounding work environment, the physical and mental states of the worker, and the quality and quantity of supervision and training. Injury can occur only when this function crosses a certain threshold and the host is exposed to injurious energy via physical contact. Certain factors that contribute to risk-of-exposure are stable for extended time periods (weeks, months, years), whereas other factors are transient (durations of minutes or seconds). The model extends classical work by Haddon and others, provides preliminary insights to designing epidemiologic studies and developing fault-tolerant work systems, and illustrates how interdisciplinary approaches can improve our understanding of the etiology of sudden-onset injuries and advancing injury research.

Causal models in conventional and non-conventional medicines

The author describes the possible causal models in both conventional and non-conventional therapies. Ontological determinism is used as a metaphysical assumption and linear causalism as a reference model. The linear causalism is here based on the following properties: sufficient condition, necessary condition, specificity, dose-response relationship, unidirectionality and externality. A subdivision of the therapy into two categories is then proposed: strong activity therapies, with strict causation, are close to linear causalism, and correspond to the therapeutic model of conventional medicine; weak activity therapies, with a much weaker type of causation, apparently tending towards indeterminacy, correspond to non-conventional medicines. Considering the internal state of a human being as a causal factor of therapeutic response, the difficulty in interpreting weak activity therapies is in part resolved and the differences with the strong activity therapies are also less pronounced.