The Central Pollution Control Board (CPCB) provided daily data on air pollution levels collected at the nine monitoring stations located throughout the city. Six of these monitors have been in operation since 1987 and are operated directly by the CPCB. The other three monitors, added to the monitoring network in 1990, are operated on behalf of the CPCB by the National Environmental Engineering Research Institute (NEERI). Readings of total suspended particulates (TSP), sulfur dioxide (SO2 ) and nitrogen oxides (NOj) are taken at each station on a rotational basis approximately every three days. The data include average, maximum.
