During a recent legislative compliance audit we received a non-conformance relating to our failure to develop and implement a formal requirement, either by contract or procedure, to ensure that contractor labour resources participate in a hearing conservation program, including an initial and on-going audiometric testing. We also failed to implement a formal medical surveillance and approval process for personnel assigned to use respiratory protection equipment.
The current medical assessment for contractor personnel is limited to a general medical screening questionnaire, given to the prospective agency employee prior to being offered a position. This is controlled by the labour supply contractor.
Our company occupational health standard states that contract personnel are subject the requirements of our standard where appropriate. This would include baseline medical assessments as well as surveillance assessments.
Due to our site being a project site, the longevity of employment for the contract labour varies tremendously and can be very sporadic, making the implementation of a medical program difficult to implement and manage.
I would like your opinion on the following please:
Is a general medical screening questionnaire a suitable substitute for a baseline medical?
Is the employer (labour supplier) responsible for conducting baseline medicals and health surveillance, or the hirer (my company)?

Due to the nature of the project works (duration and infrequency) should a baseline medical be conducted each and every time the contractor starts working at our site?
Thanks in advance to those who are able and/or willing to comment.