You really need to challenge the contractor - this may not be a doctors fit to return to work scenario but it is highly likely some form of "private" medical declaration in which case has the cost been included in your price?

Depending on what has to be declared, if any testing is required, it could also delay site attendance.

These matters should really have been addressed before orders were taken as part of the contract and its specification

I came across this when working for a small company installing cabins on (quite large) sites. Usually a big name PC deciding on contractor 'rules'. This one insisted on a medical certificate for our staff doing what was termed by them as 'safety critical'. For a couple of minutes assisted in the positioning of the cabin on the ground by the hi-ab operator. 

After querying this, and following up on the 'quotes' I was given, I found some HSE research and very specific industry codes referring to safety critical jobs. In the original research this was limited to EMPLOYING people in what most of us would regard as safety critical, quite limited, but bit by bit and with the construction industry penchant for over-egging, this definition has been stretched to include anyone from any organisation (not direct employees) who might briefly assist a plant operator (that role possibly being genuinely safety critical).

One client wanted us as contractors to fill in a 23 page online medical questionnaire. Quite rightly our worker declined, unclear as to why his personal medical history was any concern of a third party. Then we were asked to get a medic (our expense) to provide this SC 'certificate' on the basis that he 'might assist a reversing vehicle' whilst on site.

So this group of 'safety critical workers' started out being the plant operator, but is now anyone termed slinger / bansksman / traffic marchall (find clear definitions of these if you can!) 

"In some activities the consequences of adverse events may be serious and the term “Safety Critical Work” has been used. Safety critical work (or roles) were defined in the Faculty of Occupational Medicine’s “Guidance on alcohol and drug misuse in the workplace” 2006 as;- “ those involving activities where, because of risks to the individuals concerned or to others, the employees need to have full, unimpaired control of their physical and/or mental capabilities…”. In the construction industry it would seem appropriate to make a distinction between those employees who, by virtue of the nature of their work, are potentially in a position which could increase the risk to the health and safety of others, whether these be other employees or third parties, and those employees where the increased risk is only to themselves"

The "herd" (Construction Industry) are great at adding more complex and unecessary rules for fear of missing something.

If they put as much effort in to employing knowledgable rather than certified/carded/ticketed persons to implement the designs and not trying to "value" engineer we might possibly see safer constructions.

Does someone pushing fire stops behind cladding or between brickwork count as "safety critical"?  The absence or miss-fitting of such items for the future user would indicate so.