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Polycyclic aromatic hydrocarbons (PAHs) are a class of more than 100 chemicals that occur naturally in coal, crude oil, and gasoline, and are also present in products made from fossil fuels, such as…

A water quality variance is a temporary change in a state's water quality standard for a specific pollutant and its relevant criteria, allowing deviation from meeting a water quality-based effluent limit for a particular discharger.