It is a common fear of people that rat feces or rat hair may contaminate many foods that we eat.
Anywhere there is a human population and therefore a variety of food sources, there is likely to be an associated rat population, as well.
This means that the processing facilities for many of our foods also likely have rat infestations, and this could potentially contaminate food sources.
In the United States, food manufacturers are strictly regulated and large, uncontrolled rat populations in factories which could cause major contamination are unlikely.
With that being said, it is inevitable that trace amounts of rat feces and rat hair would make their way into the food supply, but it is at such a low level that it is not harmful to humans.
I find it helpful to look at the situation this way: we eat pounds of dust and dirt along with our food every year due to inevitable contamination, and it is likely that the also you trace amounts of rat parts as well, but it is not likely to hurt us.