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Types of Food Contamination

Last updated on 30th March 2023

Food contamination is a global safety concern, with 1 in 10 people falling ill each year due to eating food that has been contaminated. As a result, businesses are obligated to ensure they uphold the highest standards of food safety.

A failure to ensure that all food products are safe for consumption could have a catastrophic impact.

A contaminant is any substance that has been added to food that should not be there. Food can be accidentally or intentionally contaminated, with contaminated food posing a serious risk to the consumer. This guide will explore the different types of contamination and how they are likely to occur. The four main types of food contamination are chemical, microbial, physical, and allergen, and we will discuss these further. We will also answer questions such as, what are the types of contamination, and how can you prevent food from becoming contaminated? Throughout this article, we will also refer to current UK guidance and the relevant food safety standards.

What is Food Contamination?

Ultimately, food contamination is when something gets into food that should not be there. Contamination can happen anywhere where the food is being handled or at any stage of the manufacturing process. However, the main vulnerabilities are in the production and supply chain.

Many scenarios could result in contamination, and a single case can have long-lasting ramifications to your business. It is not always obvious whether food has been contaminated. For example, food that has been contaminated with chemicals or bacteria may not look or taste any different to food that has not.

Accidental and Intentional Contamination

There are two different types of food contamination, accidental and intentional.

Accidental: Accidental contamination results from unintentional human actions, unexpected events, and human error. This could also include machinery or equipment breaking, like a piece of plastic getting mixed into a cake or metal shavings from a broken machine part. It may also be because of improper handling procedures. As people may be aware of the incident taking place, accidental contamination is more likely to be dealt with before the product hits the market. However, even if the item has not reached customers yet, a risk assessment will still need to be conducted.

Intentional: Also known as food fraud, intentional contamination is a growing concern. It refers to deliberate acts of contamination, and it is a criminal act. This can occur at any point, and the perpetrator could be anyone from a stranger to an employee.

The Impact of Food Contamination

In the modern globalised world, food contamination can have far-reaching impacts on the lives of the people it affects. A report by the World Health Organisation (WHO) stated that:

‘Food contamination that occurs in one place may affect the health of consumers living on the other side of the planet’.

In the UK, all businesses must adhere to food safety responsibilities as outlined by the Food Standards Agency. If a business is aware that food has been contaminated and it is unsafe, they will need to do a product recall. Product recalls are a costly business. They involve a crisis team, the removal of the product, a full investigation, and money spent on public relations. As well as being expensive, they can damage public opinion and affect consumer trust. However, a failure to recall products could have worse consequences.

In recent years, the number of product recalls by companies has increased rapidly. However, despite some growing fears, not all of these were conducted ‘just in case’. Statistics also show there has been a dramatic increase in the number of cases of food contamination. Food contamination can ultimately result in serious consequences. Physical contamination could pose as a choking risk, high levels of chemicals in food could cause fatalities or long-term illness, and microbial contamination could cause food-borne illness. For most people, food poisoning does not have long-lasting effects. However, each year around 600 million people around the world are ill because of food-borne illness. Furthermore, 33 million people die due to some form of food poisoning each year. Consequentially, UK businesses that fail to comply with standards are appropriately penalised.

Woman suffering from food poisoning after eating contaminated food

Types of Food Contamination

There is some dispute regarding how many different types of food contamination there are, with some saying there are three and others declaring four. Both cover the multiple incidences that could occur. The three types of contamination are biological, physical, and chemical. However, for the purpose of this article, we will discuss four categories. These include chemical contamination, physical contamination, microbial contamination, and allergen contamination.

Chemical Contamination

Chemical contamination is when the food becomes contaminated by some form of chemical. It is the most difficult type of contamination to control, and it could potentially result in acute poisoning and long-term diseases. Symptoms of chemical contamination can range drastically. In most cases, the consumer will experience some form of mild gastroenteritis, but in some situations, chemicals in food can be lethal.

In recent years, there has been a wider interest in the impact of chemicals in our food and the potential effects on consumer health and wellbeing. For example, studies have shown that prolonged exposure to low levels of carcinogens can increase a person’s likelihood of being diagnosed with cancer.

Natural and Artificial Contamination

There are two different types of chemical contamination, natural and artificial.

Natural chemical contamination refers to the existence of chemicals that occur naturally in food. These are regulated, and the government has prescribed minimum limits for those considered harmful. Thus, food production and manufacturing businesses have a responsibility to ensure there are measures in place to prevent products from exceeding these limits.

Artificial chemical contamination results from food being contaminated with a chemical that is not a natural by-product of the food. This could include chemicals used for cleaning and disinfection, fertilisers, and pesticides, amongst others.

Most Common Types of Chemical Contamination

Some of the most common examples of chemical contamination include:

  • Cleaning products and disinfectants.
  • Unwashed fruit and vegetables.
  • Chemicals from the use of non-safe plastics.
  • Pest control chemicals.
  • Antibiotics.
  • Anti-inflammatory drugs.
  • Corticosteroids.
  • Heavy metals.

Avoiding Chemical Contamination

Some of the best ways to prevent chemical contamination from occurring include:

  • Always store chemicals separately from food, including cleaning products.
  • Always keep food covered whenever possible.
  • Make sure chemicals are properly labelled.
  • Do not use poison in the same room as food is manufactured or prepared.
  • Use utensils resistant to acid and salts.
Frozen food covered in plastic food bags to prevent chemical contamination

Physical Contamination

Physical contamination refers to food that has been contaminated by a foreign object. Finding random objects in our food is certainly off-putting, and it is definitely something that causes concern for consumers. Food that has been contaminated by a physical object could directly pose as a choking risk and cause serious injury. Furthermore, the object may also carry bacteria, which could cause microbial contamination at the same time.

The most common objects to contaminate food include glass, hair, metal, jewellery, dirt, and fingernails. Physical contamination of food may also be from the environment including the building and the equipment you are using, such as plaster, flakes of paint, and screw fixings. Moreover, physical contamination could also occur because of issues with packaging, such as staples, string, polythene, and cardboard. However, some physical contamination can occur naturally, like insects entering fruit and vegetables or bones in boneless fish. However, regardless of whether it is a natural component of the food, businesses must still find out how it got there and how to avoid reoccurrence of the incidents.

Avoiding Physical Contamination of Food

Physical contamination of food is a global safety concern, and product recalls can cost millions, as well as damaging the company’s reputation. As a result, businesses have a responsibility to prioritise customer safety and it is important that they do their utmost to prevent physical contamination. Some ways of avoiding it include:

  • Take products out of delivery packaging and store in food-safe containers.
  • Have a no glass policy in place to prevent the risk of broken glass contaminating the food.
  • Plasters should be bright blue, so we can easily see them if dropped.
  • Keep the premises maintained to prevent environmental hazards.
  • All ingredients used should be washed thoroughly to remove hazards.
  • Hair should be tied back, with a hair and beard net where possible.
  • Workers should wear gloves when handling food.
  • Fingernails should be clean, short and unpolished, with no long or false nails.
  • Staff should not wear jewellery. However, most companies permit staff to wear a simple wedding ring.

Microbial Contamination

Microbial contamination, also known as biological, is the most common cause of food poisoning. It is basically the existence of harmful pathogens in food, like microorganisms, bacteria, viruses, mould, fungi, and toxins. This is the leading cause of food-borne illness and food poisoning, and food spoilage or waste is the most common cause of it. Chilling food causes the pathogens to become dormant but does not necessarily prevent the growth of bacteria. To ensure bacteria are destroyed during the cooking process, foods should be cooked thoroughly to the right temperature. However, it is noted that many microbial toxins are heat resistant and spoiled food should not be cooked and consumed. The most common food-borne illnesses include norovirus, salmonella, listeria, e.coli, and campylobacter, and symptoms can range from mild gastro issues to fatal and long-term diseases.

Microbial contamination can occur due to either direct or cross-contamination. Direct contamination is a result of the pathogens already produced in the food reaching unsafe levels. An example of this would include the bacteria and toxins found in spoiled meat. Whereas cross-contamination is when pathogens enter food from other sources and multiply to unsafe levels.

High Risk Foods

Some foods are considered to be a high risk of microbial contamination. The nature of these foods particularly provides an environment in which bacteria can thrive, with the provision of food, water, and neutral acidity. Some examples of these are:

  • Meat.
  • Poultry.
  • Rice.
  • Dairy products.
  • Cooked and raw eggs.
  • Seafood.
  • Unpasteurised juices.
  • Prepared fruits and vegetables.

What is the Danger Zone Temperature?

The danger zone is anything between 5°C and 63°C, with food kept at these temperatures being particularly prone to microbial contamination. In such ideal conditions, bacteria double their numbers every 20 minutes. This means that one cell of bacteria can become 2 million in just seven hours.

Avoiding Microbial Contamination

Some tips for avoiding this type of food contamination include:

  • Use a thermometer to ensure food is thoroughly cooked.
  • Raw meat should always be stored separately to cooked meat.
  • All equipment and utensils should be washed and cleaned regularly.
  • Food should be covered at all times.
  • Respect use-by dates.
  • Fruits and vegetables should always be washed thoroughly.
  • Food handlers need to always practice excellent hygiene. This includes washing hands regularly, and after coughing, sneezing, or touching their hair or face.
  • Regularly check the temperatures of refrigerators and freezers.

Allergenic Contamination

A food allergy is due to the way the body reacts to a specific food, with the body’s defence system perceiving the substance to be a threat. In the UK, around 5,500 people attend the hospital per year due to an allergic reaction, a figure which has been increasing since the 1980s. In fact, in the 20 years before 2012, the UK had seen a 615% increase in the number of people being admitted in hospital with anaphylaxis. This refers to an acute life-threatening reaction, during which the body releases histamine to attack the allergen. A person experiencing anaphylaxis will require emergency medical attention, and it can be fatal.

All businesses that produce food have a responsibility to be aware of the dangers of cross-contamination as even trace amounts of an allergen can cause such a severe reaction. As a result, strict laws are surrounding this, which businesses must adhere with to ensure customer safety. Companies must ensure that they have a strict system in place to prevent cross-contamination of the 14 main allergens.

Cross-contamination can occur at any stage, including during primary food production, harvest, slaughter, secondary food production, transportation, storage, distribution, preparation, and serving. Due to the nature of the business, some manufacturers cannot prevent trace contaminants of allergens contaminating the food. If reasonable adjustments cannot be made, they will need to add a precautionary allergen statement to their labels; for example, ‘May Contain Nuts’.

14 Main Allergens

Any foods can trigger an allergic reaction, but some of these are considered to be more dangerous than others. The 14 different allergens must be clearly marked and labelled. These include: nuts, peanuts, eggs, milk and dairy, crustaceans, molluscs, cereals containing gluten, celery, lupin, mustard, sesame seeds, soya, and sulphur dioxide (when added and over 10 mg per kg).

Muffins containing 3 of the 14 allergens

Avoiding Allergen Contamination

Businesses must take appropriate measures and have a system in place to prevent cross-contamination of allergens. Some steps could include:

  • All foods should be clearly labelled if they contain the 14 allergens discussed above.
  • Hands should be washed frequently and properly.
  • Thoroughly wash all equipment after each use.
  • Use separate equipment for food products that contain allergens.
  • Take swabs to test for the existence of allergens.
  • Store food containing allergens separately, with storage containers clearly labelled.

Preventing Food Contamination

Some of the best ways to prevent contamination involve:

Hygiene: In all aspects of food prep and manufacturing, cleanliness is essential, and all surfaces and equipment should be cleaned thoroughly. Personal hygiene is also important. Food handlers should wash their hands regularly and wear gloves and a hair/beard net to prevent physical contamination.

Storage: Food must be stored properly to prevent contamination during this stage. It should be covered and in containers that are clearly labelled. Chilled foods should not be left at room temperature. Furthermore, refrigerators should be between 1°C and 4°C and commercial freezers should be below -23°C.

Maintenance: In order to prevent physical contamination, maintenance of the premises and equipment is also essential. Things that are broken should be fixed promptly and recorded appropriately.

Food preparation: Care must be taken during the preparation and cooking of food to prevent contamination. Food must always be cooked to the correct temperature, and you should use different equipment and utensils for cutting and preparing raw meat.

Staff training: To prevent the risk of contamination, businesses are responsible for ensuring staff have received appropriate training regarding food safety and handling.

Quality control and testing: Accidents happen and mistakes can occur, which is why quality control and testing is one of the most important stages in manufacturing. Businesses should also have a strong tracking system. They should know where the product has come from, where it went, and where it ended up.


Foodborne illnesses are a major international issue, and product recalls can have a lasting impact on a business. Anyone who handles food has a responsibility to comply with the health, safety, and environmental standards that are set out by law. Noncompliance can not only have an impact on the business’ reputation, but sometimes result in death or injury. This article has broken down the four main types of food contamination: chemical, microbial, physical, and allergenic. It has also highlighted a number of different scenarios that could cause the contamination of a food product and numerous ways of preventing it from occurring.

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About the author

Sarah Wilkinson

Sarah Wilkinson

Sarah graduated in 2012 from Trinity St. David, University of Wales, with a 1st class honours degree in Social Inclusion and Justice. After her studies, she taught English around the world for almost 8 years, spending several years in Turkey and Spain.

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