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Key Factspending-external-review

  • U.S. shell egg production totaled 7.96 billion as of June 2014, which is 3% percent higher than it was in 2013. It is estimated that for every 100 hens, 76 eggs are produced per day.
  • A 2010 multistate outbreak of Salmonella Enteriditis was attributed to eggs following an investigation by the Centers for Disease Control and Prevention (CDC). The source of contaminated eggs was linked to two Iowa farms and a recall of potentially affected eggs was put into effect. Between May and November 2010, approximately 2,000 illnesses resulted from this outbreak making it one of the largest foodborne outbreaks associated with eggs in recent history.
  • Salmonella spp. is the primary pathogen that infects shell eggs. Listeria monocytogenes and Campylobacter jejuni have not been linked to any foodborne outbreaks with shell eggs, but they are a concern with processed egg products and poultry meat, respectively.
  • Conventional and free-range or free-roaming are the two main types of egg production systems in the U.S. According to the United States Department of Agriculture (USDA), producers must demonstrate that hens have had access outside in order to be classified as free-range.


The top five egg producing states are Iowa, Ohio, Indiana, Pennsylvania, and California, which account for 51% of laying hens. There are 177 companies that represent about 99% of all laying hens. These companies have flock sizes of 75,000 or more birds, 60 have flocks of 1 million-plus, and 17 have flocks of 5 million-plus.

In 2013, the per capita consumption of eggs in the U.S. was 251.3. Per capita consumption is projected to continue increasing in the coming years.

Of all shell eggs produced in 2013, 53.3% went directly to retail sales, 32% were further processed, 10% were utilized by the foodservice industry, and 4.7% were exported. Specialty egg production accounted for 5.7% of all egg production as of May 2014, with 2.9% being certified cage-free and 2.8% being certified organic.

Foodborne Outbreaks

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Hen laying eggs in coop.
Hen laying eggs in coop.

Conventional and free-range or free-roaming are the two main types of egg production systems in the U.S. According to the United States Department of Agriculture (USDA), producers must demonstrate that hens have had access outside in order to be classified as free-range. Other systems, such as cage-free, are not legally defined by the USDA and are used for marketing only. Recently, raising backyard poultry has become an increasingly popular trend in urban areas throughout the country. Unfortunately, not all first-timers fully understand the care that raising chickens requires, which can lead to foodborne illness if coop maintenance and handling of eggs are not done properly. Proponents of backyard chickens claim that they are raised under more natural conditions, which benefits the birds. Commercial egg producers claim that their hens are better protected from predators and disease due to the implementation of biosecurity measures and their ability to individually examine and tend to each hen.

Regardless of the type of system, an environment that is stressful to hens can lead to an increased risk of foodborne pathogen transmission for two reasons. First, stress functions as an immunosuppressant, which can lead to a higher rate of infection with Salmonella among hens. Second, hens infected with Salmonella are more likely to shed the bacteria when stressed.

Layer hens begin producing eggs around 19 weeks of age. The total time it takes to form an egg is around 25 hours so most hens lay an egg every day. Eggs are usually laid between 7 and 11 a.m. and 30 minutes after her egg is laid the hen begins producing tomorrow’s egg.

Most commercial egg production operations function in the same, highly automated fashion. Computers control the distribution of feed and the lighting in the hen house to optimize nutrition and egg yield. Hens live in stacked cages with floors that are slotted and sloped so that manure does not collect and the eggs gently roll onto conveyor belts. This feature, along with good ventilation and airflow, helps keep the hen house clean and reduces egg contamination.

Both the interior and exterior of eggs can become contaminated with foodborne pathogens. Interior contamination can occur via the transovarian route when bacteria within the intestinal tract of the hen end up in the yolk and egg white before the shell forms. Because eggshells are porous, bacteria can make their way to the interior of the egg if the exterior is contaminated. If the poultry house has poor hygienic standards, fecal matter present in the environment will contaminate the exterior surface of the egg.

Processing of Eggs

Egg laying hens in battery cages. Source: Farm Sanctuary.
Egg laying hens in battery cages. Source: Farm Sanctuary.

After being collected, the eggs are disinfected with soap and 100°F water before being dried and inspected for cracks and blood spots in a process called candling. During the candling process, eggs are carried along a conveyor belt over a light source and mechanic sensors that identify defective eggs for segregation. Candling may be done by hand at certain intervals for spot checking to ensure accuracy in the grading system. After being weighed and inspected, eggs are classified by grade and size according to USDA standards. Eggs of the highest quality are graded as AA, flowed by A and B. Grade B eggs do not usually make it to the shelves and are instead used to make processed egg products. Grading is based on the interior quality of the egg as well as the condition of the eggshell. The USDA grading system is optional; producers that opt out must have their eggs inspected for wholesomeness by state agricultural departments. Eggs are not individually sized; the total weight of a carton of one dozen eggs determines whether the carton is labeled as jumbo, extra large, large, medium, small, or peewee.

Storage and Transport of Eggs

The U.S. Food and Drug Administration (FDA) Egg Safety Final Rule went into effect in 2010 to reduce foodborne illness caused by Salmonella Enteriditis in eggs. Producers with 50,000 or more hens, which account for approximately 80% of the egg industry, must comply with the rule. One of the stipulations of the rule requires all eggs to be refrigerated at 45°F no later than 36 hours after the eggs are laid to prevent bacterial growth. The same temperature requirements exist for storage and transportation of eggs throughout all steps in the egg production process: from the farm to the retailer. Dating of egg cartons and individual egg marking are optional. If used, expiration dates cannot exceed 30 days past the packing date of the carton and use-by dates cannot exceed 45 days past the packing date.

Additional requirements of the FDA’s Egg Safety Final Rule include establishing pest control measures and implementing biosecurity measures on the farm to prevent environmental contamination.

Food Safety


The FDA enforces shell egg regulations while the USDA is responsible for overseeing the safety of egg products, however there is some overlap in their responsibilities. Under the USDA, the Animal and Plant Health Inspection Service (APHIS) launched the National Poultry Improvement Plan (NPIP), which certifies hatcheries as free of certain diseases. The Food Safety and Inspection Service (FSIS), also under USDA, verifies that shell eggs are stored and transported at the proper temperature.

Egg Safety for the Consumer

Eggs with runny yolk.
Eggs with runny yolk.

Buying eggs that are refrigerated and unbroken, refrigerating eggs immediately when returning home from the store, and following use-by dates are good starting points for preventing foodborne illness. Practicing good food safety skills at home, including hand washing and cleaning utensils and surfaces that have come into contact with uncooked eggs, is also important to prevent contamination in the home.

A common misconception is that if an egg floats in a bowl of water it is bad and should be thrown out, but this is not necessarily the case. An egg will float when the air cell inside the egg is large enough to make it buoyant, which indicates the egg is old (freshly laid eggs have virtually no air cell). However, the egg may be perfectly safe to eat permitting it does not have an off-odor or unusual color when opened.

It is not advisable for anyone to consume raw or runny eggs, especially those with weakened immune systems. Foodborne pathogens can be present in both the yolk and the albumen, or egg white. Eggs should be cooked until firm and egg dishes must be heated to at least 160°F in order to sufficiently kill harmful bacteria. Pasteurized eggs and egg products should be used to make dishes that call for raw eggs, such as homemade Caesar dressing.

Proper temperature control of eggs and egg products will prevent bacterial growth. Condensation that forms on eggs left at room temperature can lead to interior contamination of the egg. Bacterial growth is inhibited outside the range of 40°F to 140°F so hot eggs dishes must remain hot and cold egg dishes must remain cold. Consumers are advised to discard cooked eggs or egg dishes that have been left at room temperature for more than 2 hours.

Egg Products & Food Safety

Egg products include whole eggs, egg whites, and egg yolks with or without non-egg ingredients that have been pasteurized and processed. Egg products come in liquid, frozen, and dried forms. Consumers should observe use-by dates and store egg products according to package instructions.


In 2014, Americans consumed an average of 263.0 eggs per person.  Egg consumption per capita has continued to increase in the United States. Within the past two years, the egg industry estimates that consumption has increased by nine eggs per person. Consumption of eggs reached its maximum in 1945, where people were eating an average of 402 eggs per year.  Contrary to this, American egg consumption was at its lowest in 1995, where it fell to an average of 232 eggs per person.  In the 2006-2007 Population Survey Atlas of Exposures, 75.4% of the survey cohort reported eating fresh eggs within the past 7 days. Furthermore, 27.6% of the survey cohort reported eating any food item that contained raw eggs.

Information on storing eggs for quality and freshness can be be found at FoodKeeper App.


Costing around 15 cents each, eggs are one of the least expensive, healthiest foods available. For only 70 calories, one large cooked egg contains many vitamins and nutrients that promote eye health, weight management, muscle strength, and brain health.

Most of the fats found in eggs are monounsaturated and polyunsaturated fats, which help stabilize blood cholesterol levels, contributing to a healthy heart.

Eggs support eye health due to high levels of vitamin A, a component of light-absorbing proteins in the retina. Vitamin A also protects membranes around the cornea and reduces the risk of night blindness. Eggs contain the antioxidants lutein and zeaxanthin in small amounts, which help prevent macular degeneration and age-related blindness.

Vitamin D found in eggs promotes calcium absorption for strong bones and teeth.

The high quality protein found in eggs prevents muscle loss in older adults and helps maintain a healthy weight by keeping people feeling full longer.

Choline is an essential nutrient found in eggs that supports a healthy pregnancy and promotes brain function.

Fortified Eggs

When chickens are fed diets that are rich in vitamins and minerals, they result is fortified eggs. The practice of supplementing chicken feed with flaxseed or fish oil to increase the omega-3 content of eggs has been adopted by commercial producers and backyard chicken owners alike. Eggs enriched with iron and vitamins A, D, and E are also available. While fortified eggs are sold at a higher premium and marketed as being healthier, the amount of these nutrients that actually ends up in the egg varies; it is important for the consumer to read the label and determine if the higher price is worth the potential health benefits.



Marisa Bunning

Marisa Bunning

Natalie Tsevdos

Natalie Tsevdos

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