The Central Pollution Control Board has been monitoring air quality in majorcities in the country. The following results by CPCB show how polluted or
otherwise is India's atmosphere.
Low levels of SO2 are observed in all the 17 cities under CPCB's study. A
decreasing trend was observed in residential areas of Delhi, Hyderabad,
Kanpur, Lucknow, Mumbai and Pune. Decreasing trend may be due to
various interventions that have taken place in recent years such as reduction
of sulphur in diesel, use of cleaner fuel such as CNG in Delhi and Mumbai.
Other measures include implementation of Bharat Stage-III emission norms
for new vehicles and commensurate fuel quality. Also there has been a
change in domestic fuel used from coal to LPG which may have contributed
to reduction in ambient levels of SO2.
Nitrogen dioxide (NO2):
NO2 levels are within the prescribed National Ambient Air Quality Standards
in the cities except Agra during most of the years. Agra being a sensitive
city, the standards are stricter. A decreasing trend has been observed in
residential areas of Faridabad, Kolkata, Solapur and Pune. Fluctuating trends in NO2
were observed in residential areas of Bangalore and Hyderabad. Vehicles are
one of the major sources of NO2 and their number is increasing
exponentially. The reasons for low levels of NO2 may be various measures
taken such as banning of old vehicles and better traffic management. The
reasons behind reduction in NO2 may be introduction of improved vehicular
technology in the form of Bharat Stage -III vehicles.
Respirable Suspended Particulate Matter (RSPM):
RSPM levels exceed the prescribed NAAQS in most of the cities but a
decreasing trend has been observed in residential areas of Ahmedabad,
Solapur and Kanpur. Fluctuating trends have been observed in residential
areas of Chennai and Kolkata. Vehicles are one of the major sources of
RSPM and their number is increasing by leaps and bounds. The reason for
high particulate matter levels may be vehicles, engine gensets, small scale
industries, biomass incineration, resuspension of traffic dust, commercial
and domestic use of fuels, etc.
Carbon monoxide (CO):
High levels of CO might be attributed to increase in vehicular population
especially passenger cars in Delhi. Despite an increase in number of
vehicles, CO levels have reduced during last few years. The decrease may be attributed
to measures such as conversion of three wheelers of CNG in Delhi.