Contaminants are substances that have not been intentionally added to food. They may be present as a result of its production, packaging, transport or holding.

What are contaminants in food?

There is a number of ways that chemical contaminants can enter our food chain via the environment, through cooking and processing, and through materials that have been used in packaging or handling (also known as food contact materials).  These chemicals can have a negative impact on the quality of food and can also lead to toxic effects if consumed at high levels or over a long period of time.

There are therefore legal measures in place to prevent contamination and ensure that products with unsafe levels are not placed on the market. Food Standards Scotland works with the Food Standards Agency and other government agencies to assess the potential food safety risks arising from chemical contaminants and take appropriate action to protect public health.

The chemical contaminants that are a priority for us are described in the sections below.

Natural toxins


Mycotoxins are naturally occurring toxic chemicals produced by certain fungus mainly Aspergillus, Penicillium, and Fusarium genera. Mycotxins are produced when environmental conditions such as temperature and moisture are favourable. Changes in weather patterns due to climate change are altering the prevalence of such toxins in food crops.

Marine biotoxins

Biotoxins can be produced by certain species of naturally occurring marine phytoplankton, and detected levels are higher in summer months. Food Standards Scotland has a monitoring programme in place that regularly monitors shellfish harvesting waters and closes areas where biotoxins are detected at levels which exceed the legal limit. The four main groups of marine biotoxins which are monitored in Scotland can cause the following illnesses:

Amnesic Shellfish Poisoning (ASP)

Caused by the neurotoxin domoic acid (DA) and its variants. ASP is characterized by gastrointestinal disorders (vomiting, diarrhea, abdominal pain) with higher doses leading to more serious neurological problems (confusion, short-term memory loss, disorientation, seizure, coma), particularly in elderly patients.

Diarrhetic Shellfish Poisoning (DSP)

Caused by a group of lipophilic toxins including okadaic acid, and dinophysistoxins (collectively known as DSTs). DSP generally causes mild gastrointestinal disorders which can last from 2-3 days including nausea, vomiting, diarrhoea, and abdominal pain, which can be accompanied by chills, headache, and fever.

Azaspiracid shellfish poisoning (AZP)

Caused by the lipophillic toxin azaspiracid and several derivatives (AZAs). To date, more than 30 AZA analogs have been identified, with three analogs routinely monitored in shellfish. Symptoms are predominantly gastrointestinal disturbances resembling those of diarrhetic shellfish poisoning and include nausea, vomiting, stomach cramps, and diarrhea. Illness is self-limiting, with symptoms lasting 2 or 3 days.

Paralytic Shellfish Poisoning (PSP)

Caused by a group of water soluble neurotoxins that are collectively referred to as saxitoxins or paralytic shellfish toxins (PSTs). PSP causes neurologic symptoms ranging from a tingling of the lips, mouth, and tongue to numbness, weakness, dizziness, and headache; and in severe cases can lead to respiratory paralysis and death.

Further information on marine biotoxins, our shellfish monitoring programme, and guidance on shellfish safety can be found on our Shellfish pages.

Environmental and Process Contaminants


Acrylamide is a chemical compound that typically forms in starchy foods when they are baked, fried or roasted at high-temperatures (120 - 150°C). When the sugar and amino acid naturally present in starchy foods are heated, they combine to form substances giving new flavours and aromas. This also causes the browning of the food and produces acrylamide. For further information visit the European Food Safety Authority website.

Dioxins and PCBs

Dioxins and polychlorinated biphenols (PCBs) are chemicals that get into our food from the environment.

Low levels of dioxins and PCBs have no immediate effect on our health but can cause problems if they are absorbed into our bodies at high levels for long periods. Foods high in animal fat, such as milk, meat, fish and eggs (and foods produced with them) are the main source of dioxins and PCBs, although all food contains at least low levels of these chemicals. The levels of dioxins and PCBs in any one individual's diet will vary depending on the amounts and types of foods they eat.

The risk to health comes from eating food with high levels of dioxins and PCBs over a long period. They have been shown to cause a wide range of effects in certain animals, including cancer and damage to the immune and reproductive systems, although it appears that people may be less sensitive.

Where do dioxins and PCBs come from?

Dioxins have never been produced intentionally. They may be formed as unwanted by-products in a variety of industrial and combustion processes, including household fires. Most industrial releases of dioxins are strictly controlled under pollution prevention and control regulations.

PCBs have been used since the early 1930s, mainly in electrical equipment. The manufacture and general use of PCBs stopped in the 1970s and is no longer permitted in the UK. The only PCBs remaining in use in the UK are sealed inside some older electrical equipment.

Dioxins and PCBs from these sources may be released in small quantities into the air, water or land. Animals and fish then take them up from their food and any soil and sediment they take in while they are feeding. The chemicals are absorbed into their body fat, where they accumulate.


Phthalates is the name for a group of chemicals that have a variety of industrial uses and are found in a wide range of household and consumer goods. In food packaging, phthalate use is limited mainly to making materials such as adhesives and some printing inks. Phthalates take a long time to degrade, or break down, in the environment. This means that they may be found at low levels in some foods. Phthalates are used as a medium to carry other substances that perfume cosmetics. They are present in children's toys, intravenous blood bags and other medical equipment, some paints and vinyl flooring. .

How could environmental contaminants affect my health?

In recent years, there has been some concern that phthalates may have a harmful effect on human reproductive development, because they have been reported to be endocrine disrupters. Endocrine disrupters are substances that can interact with hormone systems. Particular concern has focused on the sex hormones – the female oestrogens and male androgens – because of their important roles in the development of the reproductive system. Although there is evidence that some wildlife species have been affected by exposure to endocrine disrupters, there is still no conclusive evidence of a link between harmful effects on human reproductive health and exposure to these chemicals. In animal studies, phthalates have been found to affect the liver, but this is not thought to be a risk for humans at the levels of phthalates that we might consume in food.

Are phthalates avoidable?

It would be difficult to avoid them. Phthalates have been widely used for over 50 years and are found throughout developed communities around the world.


What are pesticides and how are they used?

Pesticides are substances that are used to kill or control pests. They are mainly used in farming to protect food crops. Different pesticides are used for different reasons.

For example, pesticides can:

  • prevent disease in crops
  • kill pests such as rats, mice and insects
  • control weeds
  • prevent mould from growing on crops while they are stored.

By protecting crops, pesticides help to provide a plentiful supply of food all the year round. If pesticides were not used, this could affect the availability and cost of food.

Are there any pesticides in the food chain?

Sometimes traces of pesticides can be left in food, or on the outside of food. These are called pesticide residues. There are strict limits on the levels of pesticide residues that are allowed to be in food. Washing or peeling fruit and veg can remove some pesticide residues.

Are pesticide residues monitored?

Yes, there is a national monitoring programme overseen by the Expert committee on Pesticide residue in food (PRiF) ), which is an independent committee of experts. This programme measures the levels of pesticide residues in many types of food, including fruit and vegetables, meat, fish, dairy products, baby food and processed foods, to check that residues are within legal and safe limits. These limits apply to food produced in the UK and imported food.

Pesticide approval process

The European Commission is responsible for the approval of active substances for use in pesticides in European Union Member States. Approval is only given after a rigorous lengthy assessment and scrutiny process which involves the European Food Safety Authority, Member States and scientific experts.

When an active substance is approved in Europe, companies can apply to the regulatory authority within each Member State, which in the UK is the Chemicals Regulation Directorate (CRD) of the Health and Safety Executive, for permission to place their product on the market.

Radiological contaminants

Radioactivity exists naturally in the environment and is also created by human activity such as nuclear power stations and military operations.

Inevitably some of this enters the food chain and levels are strictly monitored and controlled to protect public health. The level of man-made radioactivity in food and the environment is assessed jointly by Food Standards Scotland, the Food Standards Agency and the UK’s Environment Agencies and reported annually in the Radioactivity in Food and the Environment (RIFE) report.

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