Definition of Pollution: Introduction of any solid, liquid, or gaseous substance present in such concentration as may be or tend to be injurious to human, plant, or animal life, regulated under the Environment (Protection) Act, 1986.
Primary vs. Secondary Pollutants: Primary pollutants (e.g., $SO_2$, $NO_x$, $CO$) are emitted directly from sources, while secondary pollutants (e.g., Ozone $O_3$, Peroxyacetyl Nitrate - PAN) form via atmospheric chemical reactions.
Air Quality Index (AQI): India's AQI evaluates 8 major pollutants: $PM_{2.5}$, $PM_{10}$, $NO_2$, $SO_2$, $CO$, $O_3$, $NH_3$, and $Pb$, categorized into 6 distinct color-coded health impact categories from Good to Severe.
Biomagnification & Bioaccumulation: Bioaccumulation refers to the buildup of toxins within an organism over time, whereas biomagnification describes the progressive amplification of toxin concentration at successive trophic levels of a food chain.