effluvium

Effluvium is a term used to describe an unpleasant or noxious odor or vapor emitted by a substance, organism, or environment. The word is typically used to refer to odorous effluvia rather than to liquid discharges; its plural form is effluvia. In scientific and everyday usage, effluvium emphasizes the sensory aspect of emissions rather than their precise chemical makeup.

Effluvia arise from decaying organic matter, industrial processes, waste treatment, or geothermal and other natural sources. People commonly describe effluvia from garbage dumps, sewer systems, spoiled food, or spoiled goods. While some emanations are harmless, others may indicate contamination, volatilization of hazardous compounds, or air quality concerns.

In environmental discourse, effluvium is sometimes used interchangeably with odor emissions, though it is not a strictly defined pollutant category by itself. It is distinct from effluent, which denotes a liquid discharge, and from gaseous pollutants defined in air-quality metrics. Regulatory frameworks may focus on odor intensity or odor units rather than labeling emissions specifically as effluvium.

Etymology: from Latin effluvium, from effluere “to flow forth.” The term has historical associations with miasmatic theories of disease but remains in use to describe aromatic or foul outflows in various contexts. It appears in discussions of smell in the humanities, in environmental reporting, and in some medical descriptions.