Polycyclic aromatic hydrocarbons (PAHs) pose a threat to the entire ecosystem. Although there are several hundred different PAHs, the US EPA (United States Environmental Protection Agency) has categorised sixteen (16) of them as the most hazardous to the environment and human health. One of the best known and analytically monitored PAHs is benzo(a)pyrene. Benzo(a)pyrene can be produced by both natural and human activities. It is formed naturally during the burning of fossil fuels, forest fires and volcanic eruptions. It is broken down by plants, certain types of bacteria and some algae. Human activities, such as various forms of combustion and/or pyrolysis of organic materials, release benzo(a)pyrene as a by-product in the form of smoke. Emissions from natural sources are significantly lower than those caused by human activities. As benzo(a)pyrene binds quickly with other organic and inorganic particles, the highest concentrations of this compound in the environment are found in soil, followed by water and to a lesser extent in air. Concentrations are higher in winter than in the summer months, during the day and in the soil layer of the air due to intensive human activities (heating, traffic) in densely populated areas.

All PAHs are proven to be toxic, carcinogenic and highly mutagenic compounds. Long-term exposure to these compounds increases the risk of lung damage, including the development of lung cancer, respiratory problems and heart problems, as well as weakening of the immune system. Benzo(a)pyrene is lipophilic, i.e. it is soluble in fats and only slightly soluble in water. Humans can ingest it by eating contaminated food, in which it remains in traces. Benzo(a)pyrene is formed when food is smoked, e.g. sausage products, or during thermal processing, e.g. frying and roasting food in oil and other fats, and binds to the surface of the processed food. You should therefore take particular care when preparing food on the barbecue, especially with regard to smoking and the distance of the food from the heat source. Cigarette smoke from smokers is also one of the main sources of human exposure to PAHs. In addition, contamination of food can occur through migration from the environment, especially near industrial areas and motorways where vehicle exhaust is a source. Benzo(a)pyrene is used as an indicator for the presence of PAHs due to its frequent occurrence. To reduce the risk of exposure to PAHs and their negative effects on human health and the environment, their maximum allowable concentrations (MAC) are prescribed by law. Pollution of water and soil occurs mainly as secondary pollution from the air, mainly through rain.

The “Josip Juraj Strossmayer” Water Institute continuously monitors the presence of 16 types of PAHs in surface waters in the Republic of Croatia. The MAC for benzo(a)pyrene in surface waters is 1.7 x 10^-4 µg/l according to the Regulation on Water Quality Standards, which is a very low concentration that is difficult to determine. Due to the complexity of GC-MS/MS analysis and the need for prior sample preparation, DLLME (dispersive liquid-liquid microextraction) is performed at the Water Institute “Josip Juraj Strossmayer”, which enables fast and relatively simple processing of a larger number of water samples. In view of the aforementioned challenges in determining low concentrations of this compound, the described determination method was not introduced until 2022. As a result, the assessment of the chemical status in the surface freshwater of the Republic of Croatia in 2022 and 2023 is significantly worse than in previous years. In particular, benzo(a)pyrene exceeded the MAC value at 20% of all measuring stations in 2022 and 17% in 2023. In summary, of all harmful compounds tested in the assessment of the chemical status of water, benzo(a)pyrene exceeded the MAC value at the highest number of measuring stations. On the other hand, this compound in biota exceeds the TLV at a lower number of monitoring stations than mercury and brominated diphenyl ethers. Detailed results and status assessments are presented in previous reports available at the link.

Instrument GC MSMS for the determination of the concentration of PAHs.

Centrifuge for the extraction of samples.

Equipment in the fermenter for DLLME extractions.