What kind of tumors did you find, and where were they? Skin, digestive system, urinary?
Butylated hydroxyanisole (BHA), is an antioxidant used in many foods. In most studies, as far as I know, low level doses have only been linked to cancerous papillomas of the forestomach and urinary tract. (That's not to say there couldn't be others though..)
In fact, one study
from as long ago as 1985 stated:
"These results indicate that BHA should be classified in the category of "sufficient evidence of carcinogenicity" as judged by IARC criteria."
The problem with BHA and other antioxidants (like BHT) is that sometimes they seem to act as "synergestic" carcinogens.
That means that they may not "normally" be considered carcinogens by themselves. But they can act in concert (synergstically) with other compounds to produce cancerous or pre-cancerous growths over time. It may be that for some people the other chemicals needed are provided in other ways ...diet, water, air.
For other situations, they are not present, and the animals can be exposed to even relatively high doses of things like BHA, BHT, etc ...and never develop tumors.
There are even some combinations with BHA and BHT in concert, that seem to INHIBIT the formation of cancer of the colon and liver.
Obviously, I'm not trying to dispute you, but the scientist in me is curious how you were able to determine that it was the cereals and not some other environmental factor...or even a random chance, that was responsible for the tumors you found?
I had a series of pet rats for years, ...and raised feeder mice (for my herps and spiders) for a quite a long time too.
Both groups of which were frequently treated with cereal (cheerios, total, fruit loops, etc,), in addition to produce and rodent chow. I was into sugary, "junk" cereals at the time. ...and I shared. (Not something I'd do now.)
In fact, I used fruit loops as part of the training regimen for my rats. One of my boys lived for two and a half years, and a girl lived for a little over three ...pretty long for a rat! (I did not breed them, if that makes a difference, ...which it could).
I don't recall ever having tumors in any my animals. ...that's why I'm curious how you came to this conclusion.