Safety risks? Not really. But quality risks? Yes. Bitterness, sometimes so severe they are unpalatable.

Keep in mind that canning straight citrus has limited quality success anyway. Because of the heat processing an off-flavor often results. One reason why it is recommended to can mixed citrus (oranges with grapefruit) for best flavor or use it to make jams and marmalades or chutneys instead..

So failing to remove all the seeds and pith will only increase the odds of a less than good product.

It is one example of "junk in = junk out" guideline. :)

Dave

Here is a link that might be useful: Canning Citrus

You said "Bitterness, sometimes so severe they are unpalatable"

are you saying that the seeds get bitter or are you saying the seeds turn the canned fruit bitter?

Sorry I wasn't clear. I assumed one wouldn't be eating the seeds, just the fruit.

Canning citrus causes some bitterness anyway but leaving in the seeds will turn the canned fruits very bitter.

Dave

I concur with digdirt. Leaving the seeds in will bitter the whole product. Even when you are making a jam or marmalade that you use the zest in, recipes usually tell you to remove the seeds and pith because of the bitter factor. I have come across a recipe or two where you steep the pith in cheesecloth to lend some flavor, but even those tell you to remove the seeds.