Heavy duty vehicles (hdv) using diesel fuel emits carcinogenic hydrocarbon, benzo[a]pyrene (BaP) directly to the air. A detailed investigation of BaP emissions between 1961 and 2004 was recently reported by Beyea et al. (2008, Environmental Science Technology). Consider the Baltimore Harbor Tunnel that is 2.31 km long, 6.7 m wide, and 4.1 m high. The maximum speed of vehicles within the tunnel is 80 km/h. Wind parallel to the tunnel blows in at 4 m/s. It is estimated that 2500 vehicles per hour with 12% hdv mix, moving at an average speed of 46 km/h transits through the tunnel. If the estimated emission factor for BaP was 40μg/km in 1961 and 5μg/km in 2004, what are the corresponding changes in BaP air concentrations during this period?