In 1976, a tragic release of one of the most toxic compounds known to man (dioxin, i.e., 2,3,7,8-tetrachlorodibenzo-p-dioxin) occurred in Seveso, Italy. The plant was manufacturing 2,4,5-trichlorophenol from 1,2,4,5-tetrachlorobenzene when the reaction ran away. The reactor overpressurized and the relief system opened for 5 min during which time 2 kg of dioxin escaped into the atmosphere through the plant's roof. The wind speed was 2 m/s and leak occurred on an overcast day. What is the likely concentration 10 km from the plant site?