PCB's were widely used for providing more fire resistant oils. A major use of PCB containing oils was in large oil filled power transformers and in oil circuit breakers. I worked in powerplants where the PCB containing equipment existed. The PCB containing equipment- some transformers, and some oil circuit breakers- was of a size that it could be removed intact and sent off site for disposal. The concrete floors and the gravel and soil out in the switchyards where the PCB containing equipment had been located had to be cleaned up or decontaminated.
Some of the PCB containing oils would be sent to a high temperature incineration facility for disposal. In NY State, there are two plants producing "popped shale" light aggregates for concrete. For some years, they would accept PCB containing oils and mix them with the fuel oil for the rotary kilns. Regulations tightened as far as cradle-to-grave chain of custody and final disposal methods, so I do not know where and how the PCB containing oils and PCB containing materials are disposed of nowadays.
There was a manufacturing plant in Sidney, New York which started out as Scintilla Magneto, then became part of Bendix Aviation, and then part of Amphenol. People who worked there had a variety of ailments that followed them through what was left of their lives. Some developed various cancers. The word was that the production machine tools used constant flows of PCB containing coolants. We had one man at our powerplant who had formerly been a toolmaker at the Scintilla plant, and cancer took him out at a young age. The men who knew the Scintilla plant said that all the precision grinding and production machining was run with PCB containing coolants and the air itself was heavy with the mists from it and men who worked there were soaked in the stuff.
Getting back to the hole-saw manufacturer: it is a sad commentary that the firm did not take notice of what was happening to their workers. Something as obvious as a disfiguring illness, assuming it was occurring to some numbers of working employees, should have raised a flag. On the other hand, the matter of "sole causation" enters the mix. In that part of New England, there were numerous other manufacturing plants doing all sorts of work and using all sorts of noxious substances. The maker of hole saws- not to take on their defense- may well have figured it was something in the local aquifer, or the people with the disfigurement might have worked in some other firms and been exposed to toxins there.
OSHA did not come into the US workplace until around 1976. Prior to that, I think that each state formulated its own sets of workplace safety codes and regulations. These may well have been vague, and may have gone for the obvious- issues like machine guarding, personal protection for workers like eye protection or hearing protection. Issues like exposures to toxic substances probably were not on the radar as far as state or local safety rules. About the only concern for substances that might be harmful was likely related to flammability, low flash point, or corrosivity or potential for violent reactions. At the same point in time, we have to ask whether the health hazards associated with PCB's or whatever else was in the coolants in the hole saw manufacturer's plant were known and supported by published data.
The old shops, as we know from working around old machine tools, took the view that safety was very much the worker's responsibility. This is evidenced by a complete lack of safety features on old machine tools- no safety warnings, no emergency shutoffs, no guards except on some of the otherwise open gearing. The effects of chemicals used in the workplace was not well known, let alone the long term effects. In a region such as Athol, MA, there were umpteen industrial plants making anything from tools to leather products, doing surface or pack hardening with cyanide compounds, doing foundry work with cupolas belching untreated coke stack emissions into the local air, leather working plants using all manner of tanning salts and dyes, and on it went. Firearms makers in New England were doing pack hardening/color case hardening on a production basis, and workers were hot-bluing firearms actions and barrels using a variety of chemical baths. Other than a hood with a vent stack over the worst of these areas- the heat treating areas and bluing tanks- I doubt much else was done to protect the workers. Certainly no one wore respirators or air-supplied masks when in the worst of it. A worker or even a resident of the area who did not actually work in the shops and factories was likely exposed to all sorts of toxins. Look at old youtubes of manufacturing even into the 50's and workers are seen spraying paint on various parts on a production basis without any protection other than maybe a particle filter mask. There were plating shops all over the region, doing chrome and nickel plating, and the chemicals used in the electroplating plants and resides in the plating baths are some of the worst toxins.
In short, not to defend the maker of the hole saws, but they were doing what was the status quo for the area and the times. They may not have known of a causal link between the coolants they used and the ailments their workers developed. They may have seen so much of that sort of illness in the population, regardless of which plant the workers were employed at, that they did not look further into it.
We will never know what discussions took place in the corporate offices as to incidences of employees developing this particular illness. It may well be that the corporate attorneys advised against taking any sort of notice of it for fear of opening the door for a class action lawsuit. Then, we come to the Workman's Compensation laws. In most states, Workman's Comp laws serve as a bar to further action on the part of workers injured or made ill in the workplace. The exception is being able to prove there was some "egregious breach" or "aggravated negligence" which caused workers to be injured or made ill as a result of workplace conditions.
This is a very difficult standard to meet, and the usual defense on the part of employers or businesses named as the cause of the illnesses, is to claim they were not the "sole cause" of the workers' illnesses. With many other industries in the region, of which many used noxious or toxic substances, proving sole cause on the part of the hole saw manufacturer becomes almost impossible.
Bear in mind, if you were to go to Athol, MA, you would find a classic old New England mill town. People are not affluent nor were they the types to go get a hotshot lawyer or law firm to go start an action against the manufacturers. There was also the fact that people who are born and raised in a town and have all their family and friends there are less likely to go after the major employer in the town, even if illness has occured while, or after, working in that firm's plant.
The era when the OP's client or patient worked in Athol predated the era of the accident chasing law firms with huge advertisements. Note that the OP is working with the machinist to get a workman's comp claim filed. Not a huge award like the accident-chasing law firms would have us believe they routinely get for injured workers. More likely payment to cover disability or permanent impairment and medical treatment. It is good that 40 years after the fact, a claim for Workman's Comp can still be filed.
Cutting Oil Mac: I am surprised to read of the supposed link between steam cylinder oil and testicular cancer. I always figured steam cylinder oil was more benign than most oils since it is "compounded" from tallow, rapeseed (a natural oil, also known as canola), and some mineral based oil stocks. I know I am not the only one who loves the aroma of warm steam cylinder oil. Something like gear lubricant with extreme pressure additives would seem the more likely cause of this sort of cancer.
Not to make light of things, but we joke that "you can tell who is a real machinist because they have to wash their hands before using the urinal or toilet" (being polite). I keep a pump container of handcleaner with pumice in the laundry room sink at the ready. When I come up from my shop, or in from the garage to use the toilet, the first stop is to wash my hands. Who wants anything from sulphur/lard based cutting oil to pipe dope, Prussian Blue, grease, anti-seizing paste, or lapping compound on their private parts ? Of course, working on a steam locomotive, if an engine driver or fireman had to relieve themselves, they likely peed in the coal pile or off the gangway between the cab and tender when out on a run. No way to wash up, so coal soot and steam cylinder oil wound up "you know where". Interesting thing I've noticed comparing US engine crews with British engine crews: US locomotive crews wore work gloves. British crews seem to have rarely, if ever, been seen wearing work gloves. How the British crews handled hot valve handles and hot pokers and got their hands near the radiant heat boiling out the firehole while barehanded amazes me. They probably had skin on their hands like old harness leather or worse. The US crews, wearing work gloves, had relatively cleaner hands and less chance of getting their you-know-what coated with coal soot and steam cylinder oil.