The Periyar river has borne the brunt of pollution with untreated or partially treated effluents being drained into it. Though the Periyar is a source of drinking water for thousands of people, various companies manufacturing chemicals have failed to conform to the standards on effluent treatment before letting it out into the river.

Recently, the river surface reflected shades of red, apparently owing to the effluents discharged into the Periyar. Though environmental groups had been keeping a close watch, pollution continues unabated.

A study conducted recently revealed that the Air Quality Index (AQI), a standardised measurement indicating the quality of air, in Kochi is unhealthy. According to the measurements monitored by a scientific group, some areas have considerably high pollution levels.

The AQI was calculated for Aluva, Kalamasserry, Edappally, Palarivattom, Ernakulam North, Ernakulam South, Vyttila and Thripunithura.

The concentration of oxides of nitrogen, sulphur dioxide and suspended particulate matter were considered for the calculation. The AQI readings varied from 92 in Aluva to 237 in Edappally.

An AQI measurement exceeding 100 is said to indicate air that is unhealthy, especially for asthmatic people. The air is unhealthy for the public as well if the reading is in the range of 151 to 200. AQI in the 201 to 300 range indicates very unhealthy air. A reading above 300 is hazardous.

The air quality index is denoted by internationally accepted colour codes. AQI in the range of 0 to 50, representing good air quality, is symbolised by green; 51 to 100, indicating moderate air quality, is symbolised by yellow; 101 to 150, denoting unhealthy air quality for sensitive groups, is symbolised by orange; 151 to 200, representing unhealthy air quality, is symbolised by red.

An AQI ranging from 201 to 300, indicating very unhealthy air quality, is symbolised by purple while AQI ranging from 301 to 500, indicating hazardous air quality, is indicated by maroon colour.

R. Ramabhadran Pillai