Table 1.

The four questions giving rise to suspicion of the occupational nature of a disease.

HISTORY TAKING IN OCCUPATIONAL MEDICINE
Criteria for causal relationship in epidemiology	Queries to be addressed to the patient
Temporal relationship	1. What is the time lag between the initial exposure and the start of the symptoms ?
Dose-effect relationship	2. Do the symptoms improve if the patient is not exposed any longer (e.g. if he/she changes work duties or is on holiday? 3. Do the symptoms worsen if the patient carries out specific duties or works in areas characterised by high levels of exposure?
Strength of the association	4. Are colleagues affected by the same symptoms related to the same exposure?