Food safety is an umbrella term that encompasses many facets of handling, preparation and storage of food to prevent illness and injury. Included under the umbrella are chemical, microphysical and microbiological aspects of food safety. A priority of food chemical quality is control of allergens which can be life threatening to some people that are highly sensitive. Other chemical properties of food such as vitamin and mineral content are also important and affect the overall quality of the food but are not as significant in terms of food safety. To prevent injury, the absence of foreign microphysical particles is crucial. Microphysical particles such as glass and metal can be hazardous and cause serious injury to consumers. Pathogenic bacteria, viruses and toxins produced by microorganisms are all possible contaminants of food and impact food safety.

According to the National Institute of Allergy and Infectious Diseases (NIAID) 5% of children and 4% of adults in the United States suffer from food allergies. It has been reported that as many as 200 people each year die due to food allergens (Neugut et al. 2001), although currently death certificates reflect only about 20 such deaths annually. The Centers for Disease Control (CDC) suspects that these deaths are underreported due to confusion about coding by those who fill out death certificates (CDC 2010).

Foreign objects in food products constitute the microphysical dangers. Foreign objects may include bone or bone chips, metal flakes or fragments, injection needles, shotgun pellets, pieces of product packaging, stones, glass or wood fragments, insects or other filth, personal items, or any other foreign material not normally found in food products (Hyman et al. 2001). A review of the medical literature found about 437 cases over a 21 year period (about 21 cases per year) of injury related to foreign objects in food where glass was the leading cause of injury (Gorham and Zurek 2006).

On the other hand, 9.4 million people are sickened and 1350 deaths occur each year in the United States due to 31 major pathogens that contaminate food (Scallan et al. 2011). The relative numbers of illnesses due to microorganisms makes microbiological quality the most important aspect of food safety. Thus, food safety primarily focuses on the control of contamination of foods by pathogens. Table 1 shows the breakdown of the most common causes of foodborne illness in the United States (Scallan et al. 2011). Of the 9.4 million cases estimated to occur annually in the United States, Norovirus, Salmonella, Clostridium and Campylobacter are the leading causes of foodborne illness (Scallan et al. 2011). Foodborne deaths are primarily caused by Listeria and E. coli O157:H7. In 1999, the CDC launched an effort to monitor foodborne illnesses in the United States known as Food-Net (Mead et al. 1999). In 2007, the World Health Organization initiated a system to estimate the world wide burden of foodborne diseases (Kuchenmuller et al. 2009). Together, these two data monitoring systems have greatly facilitated efforts to identify and subsequently reduce foodborne illness.

Pathogen	Estimated number of illnesses	%
Norovirus	5,461,731	58
Salmonella	1,027,561	11
Clostridium perfringens	965,958	10
Campylobacter spp.	845,024	9
Staphylococcus aureus	241,148	3
Subtotal		91
Table 1. Top five pathogens contributing to domestically acquired foodborne illnesses in the United States annually (abstracted from Scallan et al. 2011).

Many food animals can carry bacteria that are pathogenic to humans within their gastrointestinal systems. For this reason, foods primarily of animal origin were thought to cause a majority of foodborne illnesses. However, more foodborne illness outbreaks are occurring due to contaminated fruits and vegetables (Hanning et al. 2009). The number of foodborne illnesses from fresh fruits and vegetables has risen from 2% in 1990 to 16% in 2007. Thus, monitoring systems have been modified to broaden potential foods that might become contaminated.

Foods can become contaminated at any point along the production process. Thus, control programs such as Hazard Analysis and Critical Control Points (HACCP) have been designed and implemented in the industry to reduce food safety risks. Because the relative numbers of illness are due to microorganisms rather than foreign objects or allergens, HAACP plans typically focus on pathogen reduction and prevention (Gorham and Zurek 2006). However, control of microorganisms, allergens and foreign objects are considered individually rather than as a whole. Some materials are considered unavoidable and thus tolerance levels have been set. For example, in dates the allowable quantity of pit fragments is 2 pieces measuring 2 mm or longer measured in the longest dimension per 900 grams of dates (FDA 2009a). However, due to the risk and potential severity of disease certain hazards are not tolerated including contamination of products by E. coli O157:H7 or Listeria monocytogenes (2009b).Similar guidelines address food allergens and gluten in foods (FDA 2006).

Food Security

Food security has been defined by the Food and Agriculture Organization (FAO) of the United Nations (UN) as; "Food security exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life. Household food security is the application of this concept to the family level, with individuals within households as the focus of concern" (FAO 2003). The FAO estimated that a total of 925 million people were undernourished in 2010 (Fig 2), less than during the food and economic crisis of 2008–2009, but still unacceptably high (FAO, 2010). Figure 2 is based on the latest data available to FAO, dotted lines indicate estimates for 2009 and 2010 by FAO, and the United States Department of Agriculture (FAO 2010). Most of the undernourished people in the world live in developing countries, 2/3 of them in just seven countries (Bangladesh, China, the Congo, Ethiopia, India, Indonesia and Pakistan) and over 40 percent live in China and India alone. Sub-Saharan Africa has the highest proportion of undernourished with 30% of the population being in this category. Food security is affected by climate change, dependence on fossil fuels, the loss of biodiversity and use of food crops for biofuels, among many other factors

Climate Change and Food Security

The term climate change has been used in recent years to refer specifically to climate change caused by human activity (anthropomorphic climate change), and is often used interchangeably with the term global warming (Fig 2; EPA 2009). Many studies have examined the effects of climate change on crop yield. Gregory et al. (1999) determined that yields of wheat and rice decreased about 5% per degree rise above 32°C. Model simulations of maize production in Africa and Latin America predicted an overall reduction of 10% by 2055 (Jones & Thornton 2003). Stability of the food supply may be affected by an increase in the frequency or severity of such extreme events as cyclones, floods, hailstorms or droughts (Intergovernmental Panel on Climate Change 2007). However, food security relies not only on availability of food but also on ability of the household to prepare and store food and on the families' access to the available food. The ability of people to use food effectively will also be impacted by climate change by increasing the possibility for water and food borne diseases. Researchers have found that common food borne illnesses such as salmonellosis show a nearly linear increase in reported cases for each degree of increase in weekly temperature (D'Souza et al., 2004; Fleury et al. 2006; Kovats et al. 2004). Access to food refers to the ability to obtain sufficient quantity and quality of food, whether through purchasing or production. Effects of climate change on food access therefore depend on income, food prices and productivity.

Fossil Fuel Dependence and Food Security

Industrialized farming grew exponentially in developed countries after World War Two, and the Green Revolution of the 1950s and 1960s introduced the concept to many developing nations (Lucas et al. 2007). Food production worldwide increased and grain harvest increased by 250% (Lucas et al., 2007). Fossil fuels in agriculture are used to produce fertilizers and pesticides and to fuel farm machinery and irrigation systems. Skebrowski (2004) estimated that 95% of all food products require oil use in their production or processing. According to researchers at the University of Michigan's Center for Sustainable Agriculture, it takes an average 7 calories of fossil fuel to produce, process and ship each calorie of energy in food (Heller & Keoleian 2000). Fossil fuels are becoming increasingly constrained which will have an impact on food security, especially in countries that rely heavily of food imports.

Loss of Biodiversity

The term "biodiversity" is a combination of the words biological and diversity, and is used to refer to the variety of life on earth. The Green Revolution encouraged the development of "high yield" varieties in both plant and animal crops by use of interbreeding between animals or plants with desired characteristics. The FAO estimates that almost 75% of diverse agricultural crops have been lost over the last century, and fears that hundreds of the 7000 animal breeds registered in its databases are threatened by extinction (FAO 2008). According to FAO, only twelve crops and fourteen animal crop species are the basis for most of the food in the world. As biodiversity declines, the food supply becomes more vulnerable to climate change and water scarcity. Over the past few years there has been an increasing awareness of the importance of protecting biodiversity for food crops, and gene banks have been instituted. Gene banks are used to preserve genetic material, both plant and animal. Plants may be preserved by freezing cuts from the plant, or stocking the seeds. Animal genes can be conserved by the freezing of sperm or eggs in zoological freezers until further need. Coral fragments may be preserved by storage in water tanks under controlled conditions. Currently there are now some 1,750 gene banks worldwide, and in 2008 the Svalbald Global Seed Vault was opened in Norway as the definitive back-up for crop diversity (FAO 2010).

Biofuels and Food Security

Biofuels are a wide range of fuels which are in some way derived from biomass, material from recently living organisms such as grains, wood or waste. The term first generation biofuels refers to those fuels made from agricultural crops such as corn, cane or soy. Corn is the main source of ethanol for biofuels produced in the U.S., and many critics feel that using a food crop such as corn contributes to the increasing number of hungry in the world by driving grain prices higher (Walsh 2008). Second generation biofuels are made from waste biomass, such as the stalks of wheat, corn, wood, or special biomass crops (Inderwildi & King 2009). Development of biofuels has been promoted as a way to ease the effects of climate change, lessen concerns about fossil fuel usage and stimulate rural development. The OPEC Fund for International Development commissioned a study on Biofuels and Food Security (IIASA 2009). This study indicates that the development of first generation biofuels results in small increases of agricultural value but does not increase food security because of risks of deforestation and loss of biodiversity, and net greenhouse gas savings will be seen only after 2030. The study also found that second generation biofuels, if produced on land other than cultivated land required to produce food, might produce environmentally friendly and economically sound biofuels dependent upon development of technologies capable of converting cellulose to biofuels as well as land use regulations.

Summary

The challenge of food security is to assure that all people have access to enough food to lead productive lives, but a large part of food security is assuring the food is safe from a chemical, physical or biological aspect. There are numerous other aspects of food security. In this article we have discussed a few of the more prominent, including the effects of climate change on crop production, the effect of fossil fuel dependence on the import and export of food, the loss of many lines of plant and animal food stock, as well as the impact of the use of food crops to produce biofuels.

Allergen: Allergens are substances that, in some people, the immune system recognizes as "foreign" or "dangerous" but cause no response for most people.

Botulism: A muscle-paralyzing disease caused by a toxin made by a bacterium called Clostridium botulinum.

Campylobacter: A bacteria that is the most common cause of diarrheal illness in the United States.

Clostridium: Bacteria that prefer to live without air and that can cause a variety of diseases including botulism.

Deforestation: The removal of a forest or stand of trees where the land is thereafter converted to farms, ranches, or urban use.

E. coli O157:H7: A bacterium, especially connected to ground beef, capable of causing a serious, often fatal disease in children and elderly persons.

Fossil fuel: Fuels formed by natural decomposition of buried organisms dead for millions of years. They include coal, petroleum, and natural gas.

Green Revolution: A renovation of agricultural practices beginning in the 1940s significantly increasing the amount of calories produced per acre of agriculture.

Greenhouse gas: A gas in the atmosphere that absorbs and emits radiation within the thermal infrared range, including water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

HACCP: Hazard Analysis and Critical Control Points, a management system in which food safety is addressed through the analysis and control of biological, chemical, and physical hazards from raw material production, procurement and handling, to manufacturing, distribution and consumption of the finished product.

Listeria: One genus of this bacterium, monocytogenes, causes a rare but potentially fatal illness in infants and elderly people.

Norovirus: Member of a group of viruses that cause sudden diarrhea, vomiting, and stomach pain.

Pathogenic: Causing, or being capable of causing, disease.

Salmonella: a bacteria that causes diarrhea, fever, and abdominal cramps 12 to 72 hours after eating contaminated food.