The term "FAT TOM" is an acronym for "food, acidity, time, temperature, oxygen and moisture." It is used in the food service industry to describe the conditions that contribute to foodborne illnesses.
"Food" is a reminder that certain products, such as meat, eggs, milk and fish, are more likely to cause problems. "Acidity" indicates that microorganisms survive best in an environment that has a pH level between 6.6 and 7.5. Pathogens take "time" to grow, so the longer food sits out, the more likely it is to be contaminated. This growth occurs most quickly when the "temperature" of the food is between 40 degrees and 140 degrees Fahrenheit. "Oxygen" works both ways. Some microorganisms thrive in it, and some reproduce better when the environment lacks oxygen, like with home canning. Finally, pathogens prefer foods that are "moist."