In our food and air: experts from PNIPU revealed the carcinogens we encounter daily.

Carcinogens are substances or agents that can cause cancer or promote its development. They can be chemical (for instance, certain compounds found in tobacco smoke, asbestos, benzene), physical (such as ionizing radiation), or biological (like certain viruses, including the human papillomavirus).

“Doctors and scientists study the relationship between exposure to a specific substance and the incidence of cancer. They compare groups of people exposed to a carcinogen with those who have not been exposed. Similar experiments are conducted on cell cultures and animals. The ability of a substance to cause genetic mutations and alter the cell cycle is also examined,” explains Sergey Solodnikov, a scientific consultant on pharmacology at the ChemBio Research Center of PNIIPU and a candidate of medical sciences.

There are several mechanisms through which carcinogens exert their effects. Firstly, carcinogens can interact with DNA, forming adducts—compounds that disrupt cell division and growth processes. Secondly, oxidative stress. Some agents promote the formation of free radicals, which damage cellular structures including DNA, proteins, and lipids. Thirdly, chronic inflammation caused by carcinogens contributes to cancer development through mutations and increased cell division. Fourthly, harmful substances can activate oncogenes or deactivate suppressors responsible for preventing tumor transformation of cells.

Humans are exposed to carcinogens by inhaling them, absorbing them through the skin, or ingesting them via the digestive tract. These substances enter the bloodstream and are distributed throughout various organs and tissues. As a result of interactions with DNA, mutations occur. Abnormal cells divide uncontrollably, forming a tumor.

Why do some individuals develop cancer while others do not, despite common factors?

Some individuals may inherit mutations in genes that increase the risk of developing certain types of cancer, such as breast and ovarian cancer. A strong immune system helps the body recognize and eliminate abnormal cells, reducing cancer risk. Individuals with weakened immune systems, such as those with HIV, have a higher risk.

“The likelihood of oncology increases with age due to the accumulation of DNA damage and decreased efficiency of cell repair mechanisms. Certain types of cancer, such as breast and prostate cancer, may be related to hormonal levels. Chronic stress, an unhealthy lifestyle (alcohol abuse, smoking, lack of sleep), and the presence of various chronic conditions (diabetes, hypoacid gastritis, etc.) also elevate the risk of cancer,” notes Sergey Solodnikov.

Main carcinogens we encounter daily

There are more than 500 substances that are definitively or probably carcinogenic to humans. We come into contact with some of them on a daily basis.

Nitrates and nitrites are primary components of mineral fertilizers. The nitrate anion is not absorbed by the soil, so all nitrate nitrogen is in solution, readily available to plants. Nitrites—salts of nitrous acid—are present in plants in small amounts.

“The increased nitrate content in food can be attributed to the excessive use of nitrogen fertilizers. Additionally, some pesticides, such as the herbicide 2,4-D, enhance the accumulation of the substance in plants by 10-20 times,” explains Yulia Kuznetsova, an associate professor at the Department of Chemistry and Biotechnology at PNIIPU and a candidate of technical sciences.

Nitrates and nitrites can be found not only in plants and fruits. Both groups of substances have the property of inhibiting bacterial growth, thus acting as preservatives that are permitted in food production.

“They are added to certain types of cheeses, as well as meat products—sausage, ham, and smoked meats. Besides extending the shelf life of meat products, nitrites also give them an appealing pink color to the consumer,” notes Elena Shergina, a master's student at the Department of Chemistry and Biotechnology at Perm Polytechnic.

What are the dangers?

In large amounts, nitrates are harmful to health. A person can easily tolerate a dose of 150-200 milligrams of nitrates per day. 500 milligrams is the maximum allowable amount per day, while 600 mg is toxic for an adult.

“The carcinogenicity of elevated nitrate levels lies in their ability to be reduced to nitrites as they enter the saliva and small intestine with food. As a result, nitrosyl ions are formed in the blood,” explains Daria Nesterova, a master's student at the Department of Chemistry and Biotechnology at PNIIPU.

The toxic effect of nitrites in the human body manifests as methemoglobinemia. Nitrosyl ions oxidize the ferrous iron in hemoglobin to ferric iron. As a result of this oxidation, hemoglobin, which has a red color, is converted to NO-methemoglobin with a dark brown color. Under normal physiological conditions, about two percent of this substance is formed in the body. The first symptoms (dizziness, shortness of breath) are observed at blood levels of 6-7 percent. In severe cases (over 40 percent), a fatal outcome is possible, as methemoglobin loses its ability to carry oxygen throughout the body.

“Nitrates can also suppress the activity of the body's immune system, reducing resistance to adverse environmental factors. With excess substances, colds occur more frequently, and the diseases themselves become prolonged,” explains Daniil Zyanchurin, a student at the Department of Chemistry and Biotechnology at PNIIPU.

If a product contains significant amounts of proteins in addition to nitrates and nitrites, under the influence of gastric juice, amino acids (the building blocks of proteins) can form nitrosamines with nitrites. They are also formed during technological or culinary processing of food products, including during frying, smoking, and the preservation of meat and fish. With prolonged storage of food products, the concentration of nitrosamines can significantly increase. Their danger lies in their carcinogenic effects.

“In addition to methemoglobinemia and cancer risk, several studies emphasize that nitrates promote the development of pathogenic intestinal microflora, reduce the vitamin content in food, and decrease iodine levels (leading to an increase in thyroid size),” adds Lyubov Menshikova, a student at the Department of Chemistry and Biotechnology at Perm Polytechnic.

How can one reduce the impact of nitrites and nitrates on the body? Consume (or completely avoid) processed meat products, do not overcook food, and avoid burning. Eat more fresh vegetables and fruits, especially those rich in vitamin C (such as citrus fruits)—these are excellent antioxidants that neutralize free radicals. Regular physical activity will increase endurance and help the body cope better with toxins.

Exhaust fumes, tobacco smoke, and burning waste

Polycyclic aromatic hydrocarbons and their derivatives are substances formed as a result of burning household waste, incomplete combustion of petroleum products, and coal. They are also present in exhaust fumes and tobacco smoke.

“The original components found in waste are usually non-volatile and relatively safe. Their harmfulness often lies in the presence of pathogenic microflora. During combustion, a complex of oxidation reactions occurs, resulting in combustion products. In cases of partial oxygen deficiency, which often happens during smoldering, burning large masses of waste, or in closed spaces, the raw materials are not fully oxidized. Some incomplete combustion products of organic materials are extremely toxic and carcinogenic. Moreover, many of them are volatile, posing a particular danger to anyone exposed to the smoke,” explains Irina Permyakova, an associate professor at the Department of Chemistry and Biotechnology at PNIIPU and a candidate of technical sciences.

If you live in a polluted area, consider installing air purifiers at home. During peak hours, when a large amount of exhaust fumes is generated, keep windows closed. Houseplants can absorb and neutralize some harmful particles from the air. Wash curtains more often, as they accumulate pollutants.

Cooking oil

When fats are overheated (for example, during frying and smoking food), polyaromatic hydrocarbons and peroxide compounds can form. These are groups of substances that have carcinogenic effects.

“The danger of forming toxic products arises when the components of the oil begin to burn and smoke. This can happen in both home and industrial settings when cooking modes are not followed. Typically, oils are heated to temperatures of 120-180 degrees during frying and baking. If they do not burn at this temperature, the cooking process can be considered quite safe. When heated to higher temperatures, fats begin to decompose, forming toxic compounds,” explains Irina Permyakova.

Each vegetable oil or animal fat has its own smoke point, at which decomposition processes and smoke generation begin. Unrefined oils (such as olive, especially extra virgin, sunflower, corn, and rapeseed oils) have the lowest smoke points at 110-170 degrees, as well as products with a high number of polyunsaturated fatty acids (omega-3), such as flaxseed oil. They are not recommended for thermal processing and are better consumed fresh.

“However, refined oils or clarified animal fats are suitable for cooking on the stove. During refining, they are purified of phospholipids, free fatty acids, pigments, and waxy substances. These impurities decompose first when heated, so after filtration, the thermal stability of the product increases. Refined sunflower, olive, and corn oils