I think the key to terminology here is to make the statement in a negative fashion: knowledge is always limited so we can never be certain there is no relation.

I think the key to terminology here is to make the statement in a negative fashion: knowledge is always limited so we can never be certain there is no relation. It is interesting in this case to try to make the claim that because there is no correlation of cancer to proximity of cell phone use that cell phones probably don't cause cancer in nearby locations in the body. I think we have enough knowledge to make that case, but I might just be arrogant.