Well.. it's not just the chemical preservatives... but there are chemicals in those dog foods that are actually banned for use in human food because they are known carcinogens. There are some chemicals that may cause cancer or may not, but there are those that are known to actually cause cancer! BHT and BHA are two of them. They are in kibbles like pedigree. Those kibbles also contain meat (albeit a little bit of meat) which is unfit for human consumption and "thrown to the dogs". It can be meat from diseased, dying, dead animals, even roadkill! Also rendered fats and oils in those kibbles are from refuse restaurant grease. If anyone loves their pets they would never feed pedigree, iams, purina/beneful, science diet/hills, eukanuba and the like after knowning all that. Plus buying cheap disgusting unhealthy kibble doesn't pay in the long run. People who skimp on healthy food for their pets end up paying more in Vet bills. They also end up paying emotionally when their 8 or 9 year old dog is already about 14 years old with the health problems of a very very old dog. Also, there are good holistic kibbles which contain no chemical or artificial preservatives like Orijen.