I would have a long term study on insulin injected without any preservative excipients to see if it made any difference to the cancer numbers in diabetics.
I know a scientist in Sweden who has developed a filter syringe which can remove preservative (ie all those poisonous phenols we are forced to take in every day, all day, for our whole rest of our lives, the same chemicals banned in labs because they are so poisonous) as the insulin is being injected.
This was research financed by a pharmaceutical company for growth hormone as a child given growth hormone had reacted badly to the phenol. This scientist developed this filter – but then growth hormone can be dried and re;