Polycyclic aromatic hydrocarbons, known as PAHs, are complex compounds that are formed both in natural processes and through human activities. There are surprisingly many PAHs, but the Most of them are harmful to both health and the environment.
In this article, you will learn how PAHs are created, where they are found, how they affect our world, and how you can minimize your exposure to PAHs in everyday life. In the food supplement sector, PAHs are particularly relevant for resveratrol from Japanese knotweed.
Chemical properties of PAHs
Polycyclic aromatic hydrocarbons are a group of organic compounds that consist of two or more fused aromatic rings, which consist mainly of carbon and hydrogen. These rings are arranged in a flat, plate-like structure.
The chemical structure of PAHs allows them to dissolve in fat, but they are relatively insoluble in water. Their stability results from the aromatic structure, which makes them persistent in the environment. The more rings a PAH molecule has, the more stable and less reactive it is.
There are over 100 different PAHs
There are over 100 different PAHs that occur naturally or are produced by human activities. They are often divided into two categories:
- Light PAHs with two to three rings
- Heavy PAHs with four or more rings.
Light PAHs are often found in the air and can be absorbed through the respiratory tract, while heavy PAHs persist in soils and sediments and can be absorbed through the food chain (sometimes in food supplements).
The diversity of polycyclic aromatic hydrocarbons results from the number and arrangement of aromatic rings as well as the presence of different functional groups. This structural diversity leads to a wide range of physical, chemical and biological properties, which makes the analysis and understanding of PAHs complex.
Ecological impact of polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons can have profound impacts on the environment, particularly on ecosystems. They are capable of contaminating soil and water, which can affect plant and animal life.
PAHs often bind to soil particles and can remain in the environment for decades, causing long-term damage. In water bodies, they can accumulate in sediments and harm aquatic life. Benthic organisms (such as mussels and worms) that are in direct contact with contaminated sediments are particularly sensitive. In addition, PAHs can accumulate in the food chain and thus affect humans.
How do polycyclic aromatic hydrocarbons affect health?
PAHs can have both short- and long-term health effects. Short-term exposure may cause skin, eye and respiratory irritationIn some people, PAHs can also cause nausea and vomiting.
Long-term and repeated exposure, especially at high concentrations, is of particular concernIt has been linked to a number of serious health problems, including kidney, breast, and prostate cancer. PAHs are considered carcinogenic because they can cause DNA damage.
They have also been linked to impaired immune systems and reproductive problems.
Who is particularly at risk from PAHs?
Certain population groups are particularly at risk of being affected by polycyclic aromatic hydrocarbons. These include people who are occupationally exposed to high concentrations of PAHs, such as workers in the coal, oil and gas industries, road construction workers and chimney sweeps.
Children and pregnant women are also particularly vulnerable to the harmful effects of PAHs. In children, PAHs can impair development and lead to learning difficulties. Plastic toys are particularly dangerous as they are often put in children’s mouths. In pregnant women, they can increase the risk of birth defects and developmental disorders in the unborn child.
Are there limits for polycyclic aromatic hydrocarbons?
In the European Union, there are special rules that determine how many polycyclic aromatic hydrocarbons can be in products. Products for general use can only contain up to 1 mg/kg of these PAHs. For toys and things for babies and small children, the maximum permitted level is even stricter: only 0,5 mg/kg.
There is also the GS mark (“tested safety”). An important quality seal in Germany that indicates the safety of products. With regard to PAHs, the GS mark plays an important role in ensuring that products, especially those made of rubber, elastomers or plastics that often come into contact with the skin, have low PAH concentrations. To obtain the mark, 18 PAHs are examined, and these must not exceed a total content of 1 mg/kg. Even stricter limits apply to materials that can be put in the mouth or held for longer periods (0,2-0,5 mg/kg).
Limit values for food
Different maximum levels for PAHs apply to different food categories. For example, oils and fats, cocoa beans and products made from them, coconut oil, smoked fish and meat products, as well as certain processed cereal foods and other products for infant nutrition each have their own set limitsThese limits usually vary between 1 and 6 mg/kg.
Practical tips for avoiding PAHs in your diet
1. Use high-quality supplements
When buying from Resveratrol products, especially those that are Japanese knotweed originate from China, caution is advisedThere are concerns about increased levels of PAHs detected in these products. This is probably not due to the plant itself, but rather to the production processes in China. Therefore, it is important to carefully check the origin and purity of supplements such as resveratrol to avoid health risks.
2. Limit your meat consumption
Reducing meat consumption can reduce the intake of PAHs, as these are produced during meat preparation. Red meat used to be considered a scapegoat for PAHs, but we now know that poultry and fish, among other things, can also be contaminated with them.
3. Tips for food preparation
Not only the choice of food, but also the way of preparation play a crucial role. Here are a few tips:
- Use low temperatures: Cook at the lowest possible temperatures to reduce the formation of PAHs.
- Avoid direct flames: Cook food in a pan, oven or steamer to avoid direct contact with open flames.
- Remove burnt items: Remove burnt areas from food before consumption. (This way you can also remove AGEs!)
- Use marinades: Marinades can help reduce the formation of PAHs during grilling.
Sources
Books
- Sahoo, Biswa Mohan et al. “Polyaromatic Hydrocarbons (PAHs): Structures, Synthesis and their Biological Profile.” Current organic synthesis vol. 17,8 (2020): 625-640. Link
- Boström, Carl-Elis et al. “Cancer risk assessment, indicators, and guidelines for polycyclic aromatic hydrocarbons in the ambient air.” Environmental health perspectives vol. 110 Suppl 3,Suppl 3 (2002): 451-88. Link
- Srogi, K. “Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review.” Environmental chemistry letters vol. 5,4 (2007): 169-195. Link
- Mallah, Manthar Ali et al. “Polycyclic aromatic hydrocarbon and its effects on human health: An over-eview.” Chemosphere vol. 296 (2022): 133948. Link
- Melkonian, Stephanie C et al. “Gene-environment interaction of genome-wide association study-identified susceptibility loci and meat-cooking mutagens in the etiology of renal cell carcinoma.” Cancer vol. 122,1 (2016): 108-15. Link
- Abid, Zaynah et al. “Meat, dairy, and cancer.” The American Journal of Clinical Nutrition vol. 100 Suppl 1,1 (2014): 386S-93S. Link
- White, Alexandra J et al. “Exposure to multiple sources of polycyclic aromatic hydrocarbons and breast cancer incidence.” Environment international vol. 89-90 (2016): 185-92. Link
- John, Esther M et al. “Meat consumption, cooking practices, meat mutagens, and risk of prostate cancer.” Nutrition and cancer vol. 63,4 (2011): 525-37. Link
- Rafiee, Ata et al. “Exposure to polycyclic aromatic hydrocarbons and adverse reproductive outcomes in women: current status and future perspectives.” Reviews on environmental health, 10.1515/reveh-2022-0182. 2 Jan 2023. Link
- COMMISSION DECISION EU/No 1272/2013 of 6 December 2013 amending Annex XVII to Regulation (EC) No 1907/2006 (PDF) Link
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