4. Commercially produced hamburgers
Lab tests conducted by Consumer Reports have found that almost all ground beef consumed in the US contains fecal bacteria at levels high enough to cause illness. Ground beef can come from the meat of multiple animals so bacteria can be easily spread from a single contaminated cow.
A study has also shown that the meat content in some fast food hamburgers is as little as 2%. The content of meat in found in hamburgers was between 2.1% and 14.8%, an average of 12.1%. About 50% of the weight consists of water. Cartilage, bone and plant material were found in some hamburgers.