Zadeh-Deshpande (ZD) fuzzy logic based formalism for linguistic description of air quality: A case study

Communicating information on the environmental status of water, air and other parameters to the policy makers and the public at large is by indices. The US Environmental Protection Agency (EPA) formulated a uniform Air Quality Index (AQI), for the use of state and local agencies but there has been no general acceptance of the method. Many countries have devised their own methods for describing air quality. The sequel is an attempt to compare the following two methods for air quality classification using the available air quality parametric data in Chennai city of India. These methods include: 1. US-EPA´s Conventional AQI (CAQI) and Fuzzy logic based method proposed by Zadeh-Deshpande(ZD) using the concept of degree of match, without computing AQI and straightway describing air quality in various linguistic terms with some degree of certainty attached to each term. The case study relates to application of these methods to air quality data of Chennai City, India. The study reveals that the air quality description using the ZD formalism is comparable with the CAQI. The conventional method fails to capture the uncertainty which is resident in the pollutant data. Furthermore, the advantage of the second method is that, it attaches a linguistic degree of certainty to each linguistic class. In spite of variability in the perception of the experts´ there are no visible changes in the final results using Zadeh-Deshpande formalism.