What is a Chemical Hazard in Food?

Lucy Bell-Young

by Lucy Bell-Young

16th June 2021

A chemical hazard in food is when food gets contaminated with pathogens or toxic chemicals, making it no longer suitable or safe to eat. Several food additives, such as chemical preservatives, can be hazardous at high levels. Even some chemicals used in processed food are potentially harmful, with some becoming carcinogenic if a person is exposed to them over a long period of time.

What Are Chemical Hazards in Food Safety?

Possible contaminants in food include salmonella, chemicals such as pesticides, and physical contaminants like small particles of broken glass. Food safety is compromised when food becomes contaminated with these things, or when food undergoes chemical change as a result of exposure to sunlight or heat.

Bacteria and germs on vegetables under magnifying glass

For example, botulism is a serious and potentially deadly illness that’s caused by the botulinum toxin, which can accumulate in food contaminated by Clostridium botulinum (C. botulinum) bacterium. This bacterium is commonly found in preserved food, such as home-canned products, that aren’t properly washed or cooked. The bacteria grows fast in temperatures ranging from 20°C to 45°C.

Botulism causes paralysis that starts in the face and spreads to the limbs. When the toxin reaches the lung muscles, it can cause breathing failure. Early symptoms of food-borne botulism include the following:

  • Nausea
  • Vomiting
  • Diarrhea

These early symptoms are usually followed by:

  • Constipation
  • Abdominal distention

Chemical hazards can come from various sources at different stages of food production and preparation. Hazardous chemicals may already be present in the environment, leading to them getting accidentally introduced to the food.

In some cases, hazardous chemicals are produced by chemical reactions in the food itself due to how it’s processed. For example, when you grill meat on a high heat, some of the proteins can be converted into cancer-causing chemicals called heterocyclic amines (HCAs). This is particularly true in charred parts of grilled meat.

How is Food Contaminated with Hazardous Chemicals?

Here are some examples of how hazardous chemicals can contaminate food at various stages of production and processing:

  • Harvesting: Fruits, vegetables, root crops, and grains are usually treated with pesticides and fertilisers. While these foods are washed during the harvesting process, some contaminants may still remain. Similarly, milk may be contaminated by bacteria from the nipples of their animal sources.
  • Livestock and poultry farming: Food additives such as hormones, vitamins, and minerals are carefully formulated for animals to ensure they grow fast and produce more meat. However, some of these animal food additives are potentially harmful to humans in excessive amounts, which can happen if they accumulate in the bodies of livestock or poultry.
  • Slaughtering: Slaughterhouses are typically centralised and well-regulated to ensure the cleanliness of the slaughtering process. However, there are some chemicals in slaughterhouses that could potentially contaminate the meat. For example, cleaning agents, like detergents, or disinfectants, like sodium hypochlorite, could potentially contaminate the meat.
  • Processing: Many of the food items available in the supermarket have undergone some level of processing. Even “fresh” products, like fish and vegetables, have been processed and packaged before being delivered to the supermarkets. For example, ice is added to barrels and boxes of fish and other seafood items before being delivered to the sellers. The ice itself can be contaminated with chemicals like heavy metals, which in turn could contaminate the seafood. Similarly, fresh meat also requires adding ice or putting the product in refrigerated containers. As well as this, industrial scale processing of food, such as canning, requires the addition of preservatives, which could find their way into the food products.
  • Transportation: Food has to be transported from the source to the market. The risk of it being contaminated during transportation is relatively low if the food is packaged well and not exposed to air. However, some food items, especially fresh produce such as fruits and vegetables, are transported in open containers. This could lead to dust and pollutants contaminating these food items along the way.
  • Handling: When food items are delivered to the sellers, they can also be contaminated when not properly handled, especially when it comes to fresh food. For example, the conveyor belts might be contaminated, as well as the hands of those handling the food.
  • Cooking: From restaurants to home kitchens, the risk of contamination is always present. Some of the chemicals that can potentially contaminate food include cleaning agents, disinfectants, preservatives, and excessive artificial food additives.
Farmer in protective clothes spraying pesticides onto fruit trees
Foods like fruits and vegetables can be contaminated with hazardous chemicals when pesticides are used during farming

What is an Example of a Chemical Food Hazard?

Chemical food hazards are all around us. Many are intentionally added to food, but at acceptable or regulated levels. For instance, antibiotics might be added in livestock feeds to ensure the animals get bacterial infections. However, this may cause antibiotic resistant bacteria to proliferate, which could put humans at risk of being exposed to superbugs.

Here are some examples of hazardous chemicals that can potentially contaminate food:

  • Pesticides: These include insecticides, herbicides, and fungicides that can contaminate fresh produce like vegetables. Trace amounts are present in fresh food in the supermarket that are directly delivered from farms. Pesticides also accumulate in the ecosystem through biological magnification through the food chain.
  • Antibiotics: The fecal matter of livestock and poultry animals fed with high doses of antibiotics can contaminate other agricultural products. These products can harbor antibiotic-resistant bacteria.
  • Toxic elements: Heavy metals like mercury and lead can contaminate crops through the irrigation systems.
  • Mycotoxins: These are biological chemicals that are produced by fungi. Under certain conditions, the fungi that produce them grow on crops and other food products.
  • Marine toxins: Eutrophication results in the overgrowth of algae and other marine organisms. They can accumulate in shellfishes during red tide.
  • Food additives: Food colours, artificial flavourings, and preservatives can be harmful to humans in excessive amounts.
  • Veterinary drug residues: Animals that are treated by veterinarians in the course of livestock farming may accumulate some drug residues that can be absorbed by humans.
  • Processed food: Some harmful chemicals are produced during processing. For instance, carcinogenic acrylamide is produced when food products that are high in starch are fried, baked, or roasted at temperatures above 1,200°C. Products such as roast potatoes, chips, cereal, biscuits, and instant coffee often contain acrylamide.
Injection of antibiotic into raw meat
Antibiotics are often added to livestock feeds, which could expose humans to superbugs

How to Prevent Chemical Hazards in Food

As an individual, you can prevent chemical hazards in your food in several ways. Here are some examples of the things that you can do:

  • Thoroughly wash food ingredients before cooking
  • Choose fresh food rather than canned or processed food
  • Use proper heat when cooking your food
  • Avoid using too many food additives, like artificial flavours
  • Buy organically produced food

It’s worth noting that in the UK, food products have to meet stringent safety standards and quality checks, so chemical hazards in food aren’t typically things we have to worry about.


All content published on the ReAgent.ie blog is for information only. The blog, its authors, and affiliates cannot be held responsible for any accident, injury or damage caused in part or directly from using the information provided. Additionally, we do not recommend using any chemical without reading the Material Safety Data Sheet (MSDS), which can be obtained from the manufacturer. You should also follow any safety advice and precautions listed on the product label. If you have health and safety related questions, visit HSE.gov.uk.