Every now and then you hear about outbreaks of food-born illness. We hear terms like listerian and salmonella and we panic. I do suspect that some foods, usually produce items are more vulnerable than others. These are usually foods that are consumed raw. We take note of the stories of food born illnesses because they are so rare.
In general, the foods we buy at grocery stores are safe to eat. Occasionally, there are blips where some companies fail to safely process foods and people die of food poisoning or food-borne illnesses. Over the long term, overly-processed foods can cause heart attacks, diabetes and high blood pressure. It depends on how one defines "safe" in terms of consumption--we won't die 10 seconds after eating grocery store food unless we choke on it. However, a diet rich in factory-made foods can cause a host of medical maladies in our 50s, 60s and 70s.
I do not believe the food we buy in grocery stores is unsafe. Of course I wash raw produce before using it like everyone else. I realize it has insecticide on it (which actually prevents disease) but I've never become ill from it. I don't know anyone who's become ill from it. Nor do I know anyone who's become ill from preservatives in processed food, though the healthier folks don't eat too much of that.
I think the dangers of grocery store food have been oversold.
Most foods that we buy at the grocery store are not safe. People are not even told where the foods come from. GMOs are a big problem, as are corn-fed beef and pesticide use. In particular, corn-fed beef is a poison. The fats in it are unhealthy and cause heart disease. It is not sustainable (neither are pesticides).
No, I do not think foods we buy at grocery stores are safe. It's actually criminal how many foods available for sale in grocery stores are terrible for us. Aside from food with too much sugar, fat, salt, etc., there is now the prevalence of food containing genetically modified organisms (GMOs); without any laws or legislation for the foods containing GMOs to even be labeled. Many of these very poplular products and brands are illegal in other countries because of the GMOs. But because of our corrupt political process, specifically special interests lobbying, GMOs continue to poison citizens of this country; many of whom don't even know what GMOs are.