Essentially there are two main sources of dangerous or threatening additives. The first is those that are put in as part of the processing operation. These include the colourings, preservatives, flavours and flavour enhances, sweeteners, texture agents and processing agents.
Your decaffeinated coffee probably contains the solvent methylene chloride.
Your margarine contains potassium sorbate and monoglycerides.
Your sausages contain nitrites, which are known to cause cancer.
Your bread may have sodium-stearoyl-2-lactylate, caramel and calcium propionate.
Animals carry their own hidden "additives" with hormones for growth and increased milk production, antibiotics freely given to farm animals to prevent and cure animal sicknesses and residue from various chemicals given to ward off insects etc. Chickens are given mixtures containing copper sulphate, lead and arsenic to help growth and many of these remain in the meat and eventually find their way into the human intestinal tract.