There is an association between processed foods and poor health outcomes. There are some processes that have a clear causal link with poor health, most obviously the use of nitrates in meat preservation. It is not clear that all (or even most) processing is harmful.
Another aspect of this is that processed foods require less calories for your body to metabolize, since they are already partly broken down. While that doesn't specifically increase the rate of exposure to pathogens/toxicity, it does increase the net calories consumed in an already high-calorie category, and contributes to obesity.
