Safe food: a look at undesirable substances

Substances that are harmful to health can enter food in various ways. A distinction is made between residues and contaminants.

Residues are the remnants of active substances and their degradation products that remain on or in a food. These degradation products can be formed in the plant or animal metabolism or created as a result of sunlight. Even if properly used, pesticide residues can be found in food – but do not pose a health risk. Animal products can sometimes contain drug residues.

Contaminants can be unwanted by-products of food production. They can be created during the production or processing of foods of animal and plant origin. However, they can also get into the food from other sources, such as the environment. Examples of contaminants include dioxins and furans, polycyclic aromatic hydrocarbons (PAHs) and acrylamide. Food can also absorb a certain level of harmful substances from its packaging, for example phthalate plasticizers or per- and polyfluoroalkyl substances.

Pesticide residues

Pesticides are used to protect cereals, fruit and vegetables against pathogens and pests. These agents are not only important for growth, but also when storing and transporting the food. When the food is sold, it may still have pesticide residues on/in it.

Fruit and vegetables in particular can contain pesticide residues. In rare cases, food of animal origin also has such residues. This occurs if the animals have eaten feed that has been treated with pesticides.

Drug residues

All food of animal origin can contain drug residues. This includes dairy products, eggs, meat and fish from aquaculture.

One group of drugs used in the field of animal husbandry is that of antibiotics. These are used to treat bacterial infections. In particular, antibiotics are often needed when lots of animals live in stalls in a confined space.

If a farm animal is treated with drugs, a certain withdrawal period applies before its produce can be sold.

Heavy metals

Heavy metals are naturally present in the earth’s crust and can get into food in various ways. This is not automatically a matter of concern as there are some heavy metals absorbed through food that are classed as vital. These essential trace elements include zinc, iron, manganese and copper.

However, there are also heavy metals that are harmful to health, such as mercury and cadmium.

The following harmful heavy metals can be found in food:

• Cadmium: this heavy metal can be found in vegetables, edible mushrooms and animal offal.
• Mercury: organic mercury is mainly absorbed via fish and mussels. Inorganic mercury can be found in fruit, vegetables and edible mushrooms.
• Arsenic: this semi-metal is a common contaminant in food. It can be contained in rice and rice products, fish, mussels and shrimps.

Dioxins and polychlorinated biphenyls (PCBs)

Dioxins and polychlorinated biphenyls are found everywhere in the environment. They are persistent compounds that build up in the fatty tissue of animals. People absorb dioxins and PCBs by eating food of animal origin such as meat, fish, eggs and milk as well as products made with these.

Dioxins are released during combustion processes. They can be created during industrial production but also as a result of house and forest fires. They adhere to dust particles and are distributed in the environment with them.

As dioxins and PCBs are found everywhere in the environment, livestock also absorb them in their feed, to which the dust or soil particles stick.

Acrylamide and furans

Acrylamide and furans are substances that can be created when heating food. They are regarded as undesirable by-products of food production and processing.

Acrylamide is a by-product of the browning reaction. It is created when frying, baking or roasting food, i.e. when there is a high temperature and low humidity. Acrylamide formation starts at temperatures from 120 degrees and increases rapidly at 170 to 180 degrees. Certain amino acids found in coffee, cereals and potatoes increase the risk of acrylamide formation.

Examples of foods that frequently contain acrylamide include:

• Chips and crisps
• Bread
• Breakfast cereals
• Cookies and waffles
• Crispbread and crackers
• Coffee

Furans are volatile compounds that may be present in food that has been roasted or exposed to high temperatures in sealed containers. Particularly high levels can be found in the following foods:

• Coffee and cocoa
• Roasted nuts
• Toast
• Ready meals and tinned food
• Baby food

Adults primarily absorb furans via coffee. In the case of adolescents and children, breakfast cereals are among the main sources of intake. Babies and infants are most likely to absorb furan via baby food (ready-made food).

For more information on undesirable substances created when heating food, the Federal Ministry of Food and Agriculture offers a comprehensive brochure for free download.

Polycyclic aromatic hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons are found, for example, in food that has been smoked or contains smoke flavorings.

Food that can contain PAHs includes fish and meat products, soups, sauces and snacks. The PAH content of smoked food is usually higher than that of products containing smoke flavorings.

PAHs are also created when cooking meat over an open fire if fat drips onto the embers and burns. The PAHs get onto the food in the smoke that arises.

Per- and polyfluoroalkyl substances (PFASs)

Per- and polyfluoroalkyl substances are highly stable chemical substances that can build up in the human body and the environment. As they are fat, water and dirt resistant, they are used in many areas to coat materials, for example for non-stick frying pans or on coated food packaging. People primarily absorb PFASs via food but it is also possible to do so from the air that they breathe.

The Federal Institute for Risk Assessment (BfR) answers the most frequently asked questions about PFASs.

Phthalate plasticizers

Phthalates are used as plasticizers for plastics. They can be found in cables, hoses and food packaging, among other items. If food comes into contact with materials that contain phthalates, these can be transferred to it. This can occur during processing, for example, if oil is fed through hoses that contain phthalates or if food packaging contains phthalates.

The Federal Institute for Risk Assessment (BfR) answers the most frequently asked questions about phthalate plasticizers.

Further information about food packaging can be found in the “Plastic Food Packaging” (“Lebensmittelverpackungen aus Kunststoff”) brochure provided by the consumer advice center (“Verbraucherzentrale”; in German).

Pesticide and drug residues

The amounts of pesticide residues absorbed when eating food are usually so low that they do not pose any risk. The health risk of drug residues in products of animal origin is also low as withdrawal periods have to be observed after administering drugs, during which no food is allowed to be produced by the animal that was treated. The official food control administration uses controls to ensure that withdrawal periods and legally stipulated maximum quantities are met.

Dioxins and polychlorinated biphenyls (PCBs)

It is believed that some dioxins and PCBs increase the risk of cancer. Animal testing has also shown dioxins and PCBs to cause immune system and reproductive organ disorders, especially in male rats. Dioxins and PCBs can also cause liver and thyroid gland damage. In people, inflammatory skin changes (chloracne) as well as indications of liver damage or changes to the fat metabolism have been recorded in connection with the intake of very high amounts of dioxins or PCBs. However, these were triggered by accidents or deliberate poisoning, i.e. through extremely high amounts, and not through the normal intake of small amounts via food. In Germany, the levels of environmental pollution but also contamination of food and humans by dioxins have significantly reduced since the end of the 1980s.

Furans and acrylamide

The damaging effects of furans have been confirmed in animal tests, where high doses triggered cancer. Animal tests have also shown that furans can damage the liver if taken over a prolonged period. Such effects have not yet been observed in humans.

Acrylamide has also been studied using animal testing. A higher dose in food increases the probability of genetic changes and tumors. The effect of acrylamide on humans is still unclear.

Polycyclic aromatic hydrocarbons (PAHs)

Some PAHs found in smoke and smoke flavorings are suspected of damaging the human genome and causing cancer. To date, this has been demonstrated in tests on cells and animals. Some PAHs have been classed as “carcinogenic in humans”. As a result, the content of such substances in food is legally restricted and can be kept low through controlled production conditions. There are also maximum limits that have to be observed for PAH in food, including smoked fish and meat products.

Per- and polyfluoroalkyl substances (PFASs)

A heightened concentration of certain PFASs in the blood can reduce the immune response following a vaccination. It is also believed by some that heightened concentrations in the blood result in high cholesterol levels. High PFAS levels in the blood during pregnancy can cause a baby to have a low birth weight. To prevent PFASs causing health damage, restrictions already apply for some representatives of this group of substances. For example, the production of perfluorooctanoic acid (PFOA) and its precursors has been prohibited in the European Union since July 2020. Furthermore, consumer products are subject to strict maximum levels of PFOA and its precursors.

Phthalate plasticizers

There are many different phthalates with different detrimental effects on health. Some phthalates are classed as reproductive toxicants as they impair male fertility. Animal testing has shown other phthalates to damage the liver, thyroid gland and pituitary gland. To prevent such damage to humans, maximum levels have been established for all phthalates. Some phthalates are completely prohibited in food packaging. As a result, the amount of phthalates absorbed from food packaging is usually so low that it does not pose any health risk.

To protect consumers, maximum levels of most contaminants have been established with regard to food. These maximum levels are determined for the individual substances in such a way that they do not generally pose any health risks. Producers and manufacturers must guarantee the safety of the food they produce. The official food control administration also checks that all maximum levels are observed.

Further information about the basic principles of food safety can be found in the “Understanding Food Safety” (“Lebensmittelsicherheit verstehen”) brochure from the Federal Ministry of Food and Agriculture.

Consumers can also protect themselves by taking note of a few things when buying and preparing food. In addition to good food hygiene, the following measures are important:

Wash and peel food

Washing or peeling fruit and vegetables before use partially removes residues. Cold water usually suffices; there is no need to use washing-up liquid, warm water or special cleaning agents.

In the case of rough surfaces, a vegetable brush can also help. Rubbing fruit and vegetables dry after washing them also removes residues. In the case of lettuce, the outer leaves can be discarded.

Gently brown food, don’t chargrill it

Roasting, searing, baking and frying food can produce acrylamide and furan. The more food is heated, the more acrylamide or furan is produced. Fewer harmful substances are produced when food is cooked at temperatures below 180 degrees. In the case of ready-made products, it can help to follow the cooking recommendations on the packaging. When barbecuing food, it is also healthier to cook it at a lower temperature than to chargrill it.

Enjoy in moderation

As livestock and wild animal offal can contain not only heavy metals but also dioxins, PCBs and PFASs, it is better not to consume them too often. Women of childbearing age or who are pregnant or breastfeeding as well as children should particularly avoid wild boar offal as a precaution.

Wild mushrooms can contain particularly high amounts of cadmium and mercury. However, eating these occasionally does not present any health risks. If eaten regularly, people should not consume more than 200 to 250 grams of wild mushrooms per week.

If smoke flavorings have been added to a food, this must be indicated on the ingredients list. Consumers can take care to only eat such products in moderation.

Maintain a broad and varied diet

People who eat a broad and varied diet reduce the risk of consuming high amounts of harmful substances that are found in low amounts in different foods. A varied diet also helps people consume as many different nutrients as possible.