One of the many luxuries Americans enjoy is access to the safest and most abundant food supply in the world. This stems from many advances and improvements in food safety, sanitation, and crop production that reduce the chance of food-safety problems, including food-borne illness, pesticide contamination, or infectious disease. There are many reasons why food safety has become an issue. First, medical advances have made it possible for people to live longer, creating an aging population more susceptible to disease. Second, labor in the food industry is more diverse and less skilled. Learning barriers, personnel turnover, and limited food-preparation skills create challenges in training. Third, the U.S. food supply has expanded globally, and many types of food come from areas where food safety standards are less stringent than those in the United States. Other concerns for food safety stem from terrorist threats, food irradiation, and genetically modified foods.