Global agreement in specific control strategies to reduce the release of ozone depleting substances was adopted by the Montreal protocol.The treaty was originally signed in 1987 and substantially amended in 1990 and 1992. The Montreal protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere-chlorofluoro-carbons(CFCs),halogens, carbon tetrachloride, and methyl chloroform–are to be phased out by 2000 (2005 for methyl chloroform).

Stone flies are not bio indicators. Bioindicators provide a range of techniques to assess the impacts of air pollution from reactive nitrogen (N) compounds on statutory nature conservation sites. They complement physical monitoring of atmospheric concentrations and deposition and risk assessment based on the critical loads approach by providing site-based information on atmospheric nitrogen concentrations,nitrogen deposition and/or ecological impacts.

In recent years,the increases in toxic substances of NO_x and/or SPM (Suspended Particulate Matter)from vehicles come to be serious problem. About the correlation between the traffic volume in our model and the real volume, we obtained the correlation coefficient of 0.74.Simultaneously,we got the result that the concentration of NO_x was approximately 70 to 230 ppm.That of SPM was approximately 40 to 100 µg/m³.

More value of BOD means the water sample is polluted by organic matter. BOD of distillary effluent is 40000 mg/L and that of paper mill effluent and sewage is 190 mg/L and 30 mg/L respectively.

Montreal protocol which calls for appropriate action (like less production of ozone depleting substances called ODS such as CFCs) to protect the ozone layer was passed by a forum of 27 industralized countries on 16 September 1987. Till now 175 countries have joined this.

Photochemical smog is made by the deposition of dust& carbon particles on the pollutant gases and water vapours. The gases found in photochemical smog are NO₂, PAN, O₃ etc.

Biochemical Oxygen Demand (BOD) is the amount of oxygen required to destroy the organic waste by the bacteria. The more oxygen required for bacteria that means there is more organic waste. For pure drinking water it is decided less than 1 ppm and for industrial &municipal waste it is less than 10 ppm. In Yamuna water in Delhi it is about 1000 ppm.

Solar energy coming to the earth is not responsible for green house effect. It is the increase in green house gases in atmosphere like CO₂ which is released by complete combustion of fossil fuels or biomass in industries or transportation vehicles that prevent the reradiation of infrared radiation from the earth and result in increase in temperature of the earth.

Kyoto Protocol (1997) : International conference held in Kyoto, Japan obtained commitments from different countries for reducing overall greenhouse gas emissions at a level 9% below 1990 level by 2008-2012.Montreal Protocol (1987) : Industrialized countries agreed to limit production of chloroflourocarbons to half the level of 1986.

Chlorine, ozone, chloramine are used for disinfection of drinking water.