'It is at least as important to ask what man has the symptoms, as it is to ask what symptoms the man has.'
A 30-year old man presented with episodic wheeze and cough. He gave as his occupation 'panel beater' - a trade involving the repair of the bodywork of crashed cars. Further questions were therefore directed at the possibility of exposure to sprayed paint and he said that this activity did take place in the garage, but by others and in a specially constructed booth; he was not exposed to the paint. By way of explanation, he was told that some two-part paints contain di-isocyanates and that these chemicals can cause occupational asthma. He then admitted that he had a second job in which he repaired car bodywork in his own garage at home. He had been using an isocyanate-based paint spray without any exhaust ventilation or respiratory protection! This proved to be the cause of his asthma, and after he had purchased appropriate respiratory protection and ventilation equipment he was able to continue this work without symptoms.
Introduction:An inadequate occupational history may result in labelling an illness as not "occupational" when it is, or vice-versa. It may result in missing the diagnosis altogether and in losing an opportunity (or even the last or only opportunity) of making the patient better and improving the fate of other workers. As in other aspects of medical history taking, two important lines of enquiry that must be followed are questions designed to elicit information about the:
Remember that in occupational (and environmental) medicine it is just as important (perhaps more so) to ask what man has as symptoms as it is to ask what symptoms the man has.
Specific initial questions:In relation to the symptoms themselves, questioning may elicit :
A job title is not adequate, a full description of what the job entails is a bare minimum.
What does an 'electro-plater' do, or a 'ram-block packer'!? The full job description may need to go back several years - mesothelioma for example can occur 40 years after first exposure to asbestos. Indeed in some circumstances it is important to take an occupational history going as far back as the patientís first job (an environmental exposure history has rarely had to extend even to the pre-school years - as in the case of children who had played on tips containing asbestos or other hazardous substances).
The identity of any chemical exposures or other hazards must be clearly established.
Colloquial terms may be used for chemicals e.g. "trike" (trichloroethylene), "perk" (perchloroethylene), or "monkey dung" (brown asbestos). Confirmation of the identity of a chemical might involve asking the patient to bring in a label or a hazard data sheet. For example if the history is suggestive of exposure to formaldehyde, then the label of the drum should confirm this:
It is important to try and determine the duration and intensity of exposure. Determining when exposure started, when it finished and how often it was repeated may be tedious but not very difficult. However determining the intensity of exposure by history taking is very difficult but the following are useful guides :
1. How was the task done e.g. was an adhesive applied with a paint brush while the patient leant over it?
2. Was the dust concentration so bad that one could not see clearly through it, or the noise so loud that communication was difficult?
|3. If control of exposure to a chemical appeared poor,
what sort of quantities of it were handled?
4. Was there any attempt at segregating harmful tasks, or providing local exhaust ventilation? In the example shown alongside, there was significant exposure to a serious hazard, but without any adequate attempt at controlling exposure.
|5. Special questions are warranted in relation to personal
protection. A response that the worker wears a mask is about as informative
as a patient saying that he takes wee white pills. Many masks offer no
protection whatsoever against gases vapours or dust e.g. surgical masks
or old gauze masks, while "Nuisance Dust" masks of the sort often sold
in DIY shops are not much better.
Different categories of harmful agents tend to have different and specific forms of personal protection. For example, masks designed for respirable dust will not protect from sulphur dioxide or solvent exposure.
Processing the historical information, and further questions.There are a number of similarities between the processing of information in a clinical occupational medical history and the decisions regarding criteria for causal association that one encounters in epidemiology. Indeeed many good occupational physicians practise both clinical medicine and epidemiology within the specialty of occupational medicine.
Note: judgements in relation to the above should be made 'in the round'. For example: Just because a worker complaining of shortness of breath happens to be a smoker does not necessarily mean that his symptoms can be ascribed to smoking.
In conclusion, while taking an occupational history various avenues need to be explored:-
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