PAHyhdisteet

PAHyhdisteet, commonly written as PAHs (polycyclic aromatic hydrocarbons), constitute a large class of organic compounds composed of two or more fused aromatic rings. They are typically hydrophobic, with low water solubility and high affinity for organic matter, enabling persistence in the environment.

They form predominantly through incomplete combustion of carbon-based materials, including fossil fuels, wood, tobacco, and waste. They occur in automobile exhaust, industrial emissions, charred or smoked foods, soils, sediments, and air particulates; natural sources include wildfires and volcanic activity.

Environmental behavior: due to hydrophobicity, PAHs sorb to soils and sediments and can be transported over long distances on particulates. They are relatively persistent but can be degraded by sunlight and microbial action; bioaccumulate in organisms, raising exposure risks through ingestion, inhalation, or dermal contact.

Toxicology and health: several PAHs are carcinogenic or mutagenic; benzo[a]pyrene is a commonly cited marker compound. Metabolism can generate reactive metabolites that bind DNA. Risk is influenced by exposure level, duration, and compound mixture; regulatory agencies monitor PAHs using lists of priority compounds and exposure guidelines.

Monitoring and regulation: many countries use the US EPA's 16 priority PAHs as a standard set for environmental monitoring. Analytical methods include gas chromatography–mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). Regulatory measures address ambient air, drinking water, soils, and contaminated sites.