Presentation on theme: "POLYCYCLIC AROMATIC HYDROCARBONS PAHs. What are PAHs? group of organic compounds two or more aromatic (benzene) rings are fused together."— Presentation transcript:
POLYCYCLIC AROMATIC HYDROCARBONS PAHs
What are PAHs? group of organic compounds two or more aromatic (benzene) rings are fused together
potential health risk due to their inner chemical stability, high reactivity to different types of degradation and high toxicity to living organisms US EPA and in the European Union priority lists of pollutants
Physical – chemical properties Physical and chemical properties of PAHs vary with M r. PAHs as pure chemicals exist as colorless, white, or pale yellow-green solids. They are non-polar, hydrophobic compounds, which do not ionize. They have a faint odor.
Enter the enviroment PAHs are introduced into the environment mainly via natural and anthropogenic burning processes.
Enter the enviroment - Air PAHs enter air as releases from volcanoes, forest fires, residental wood burning and exhausts from cars. Some PAH particles can readily evaporate into the air from soil or surface waters.
Enter the enviroment - Water They can also enter surface water through discharges from industrial plants and wastewater treatment plants.
Enter the enviroment - Soil Most PAHs don‘t dissolve easily in water. They stick to solid particles and settle to the bottoms of lakes or rivers. PAHs in soils also contaminate underground water.
How might I be exposed to PAHs? We are most likely to be exposed to PAH vapors or PAHs that are attached to dust and other particles in the air. Sources include cigarette smoke, vehicle, exhausts, asphalt roads, coal, etc.
How likely are (PAHs) to cause cancer? Breathing or touching mixtures of PAHs and other chemicals for long periods of time have developed cancer. Some PAHs have caused cancer in laboratory animals when they breathed air containing them (lung cancer), ingested them in food (stomach cancer), or had them applied to their skin (skin cancer).
Medical tests show PAHs in the body In the body, PAHs are changed into chemicals that can attach to substances within the body. Special tests that can detect PAHs in body tissues or blood. The tests aren't usually available in your doctor's office.
Analytical determination of PAHs Samples of PAHs are mostly analysed by HPLC using fluorence detection, or by gas chromatography method with flame ionizazion detection, or mass spectrometry.
More information For more information you can visit this pages: pahs/ pahs/ 02.htm 02.htm
Vocabulary fuse - splynout lists of pollutants – seznam škodlivin pale - bledý to vary - lišit se faint - mdlý to release - uvolňovat exhaust - výfukový plyn evaporate - vypařovat se discharge - vylučování wastewater treatment plant - čistička odp. vod wastewater treatment plant - čistička odp. vod to stick - přilnout to settle - usadit se vapor - pára to develope - rozvinout se ingested - přijímat potravou to be available - být k dispozici to attach - připojit within - uvnitř body tissues - tělní tkáně