It is undoutedly at Delhi's ever-shifting borders that concentrations of toxicity are imagined. Whether it is the burning of agricultural stubble in neighboring states of Punjab and Haryana, the thermal power plants and brick kilns that dot the peri-urban and rural regions around Delhi, the movement of dust from elsewhere, or the chemically hazardous factories and household industries in Delhi's industrial suburbs where people dissemble and recycle electrical components from everywhere in the world--the toxic air in Delhi is constructed through its marginal spaces.