According to officials, these trees have a high air pollution tolerance index (APTI) and can catch and contain dust or smog, absorb pollutants and improve the ambient air quality. The Ministry has recommended that saplings of these trees be grown in the city's nurseries in large numbers and be used for systematic plantation.

Says Conservator of Forests, M S Negi: "We had compiled a report some time ago wherein we had identified and listed trees that absorbed different types of pollution. For instance, if Neem is good for absorbing noise pollution, Bamboo and Peepal are good for absorbing dust, heat and other emissions.

"The Ministry has recommended that these trees beplanted especially around industrial areas. This will create a curtain of sorts, which will absorb pollutants and save the adjoining residential areas from harmful effects."

The list is divided into four parts, based on their APTI. Part-I (which includes trees like Mango, Sehjana Phali, Kathal, Molshree, Banyan and Pilkhan) contains `evergreen trees' that have a dense canopy and can screen all kinds of pollutants if planted in large numbers.

Part-II has trees that may be raised to absorb pollutants and improve the air's ambient quality, and comprises Mango, Sheesham and Jamun.

Next on the list are species that absorb leftover pollutants: Among the 11 species, are Neem, Dhaak, Cassia, Ashok, Acacia, Kadamb, Mahua and Peepal.

The fourth part contains trees that have a low APTI but are indicators of pollution levels. It is suggested that these trees -- Kaint, Papri, Kachnaar, Silver Oak, Amla, Jacaranda, Gular -- be used to monitor air pollution levels.

Admitting that there was very little spaceavailable in and around industrial areas, Negi said: "We can plant them on roadsides, in vacant spaces along roads, gram sabha land and wherever else we get space."

Negi added that many of these species were already being grown in their nurseries and were being planted in the city as well as distributed for free to residents and organisations.

Green cover

Plants which absorb dust, temperature and emissions from traffic and industries: Neem, Bamboo, Amaltas, Sheesham, Peepal, Molshree, Mango, Jamun, Arjun Teak, Tamarind

Plants that can be used to restore and `landscape' garbage dumps: Babool, Subabool, Arjun, Gulmohar, Jacaranda, Siras, Amaltaas, Eucalyptus, Kadamb

Plants that check noise pollution: Ashok, Cassia, Neem, Kachnaar, Banyan, Peepal, Jacarand, Jangal Jalebi, Semal.

Plants suitable for areas where gaseous pollutants are dominant: Acacia, Bel-Pathar, Ulu-Neem, Siras, Neem, Bougainvillea, Sheesham, Peepal, Mahua, Hibiscus and Tamarind.