Some while ago NASA had an objective to send a man to the moon and bring him back - alive. Both a quality objective and an H&S objective for the man concerned. In terms of designing, manufacturing and operating the space ship, I'd guess that ISO 9001-style quality management of its propulsion, navigation and life support systems contributed more to H&S than ISO 18000-style H&S. Further, separating them into different management systems would have been unhelpful.
Consider an explosives factory. They don't want product to go bang except in a controlled test environment (- or after the customer got it and lobbed it at the enemy). Is that preservation of product under ISO 9001 or H&S under ISO 18000? Running two separate systems would invite duplication of effort. Where would be the harm in having a quality policy that says something like "To meet customer requirements by making product that makes a big bang on demand, in an environment that preserves the safety of our factory, workers and the local community." Such would drive design of the factory in a fashion that integrates quality and H&S requirements.
Disney's quality policy at the Magic Kingdom in Orlando FLA is something like "Every child leaves with a smile on his or her face." This single, simple, multi-purpose statement drives quality things like good rides, automatons that work all the time, familiar characters amusing the kids in the queues - and it drives safey, for kids don't smile when the roller coaster leaves the rails. Again, much of the safety is delivered with quality management techniques like track inspections, maintenance schedules, design and manufacturing processes that incorporate safety considerations ... I saw a TV documentary somewhere that showed roller-coaster maintenance engineers take the cars and tracks apart for annual maintenance, put them all back together, then go themselves on the first ride - is that high class ISO 9001-style validation or what?
For the auditor, why not audit quality aspects against ISO 9001 and safety against their own safety procedures - which might be incomplete by ISO 18000standards, but surely better than nothing. I'd rather a safety harness without a hazard assessment, than none at all.
Hope this helps,
Pat