While most of the 167 Durga idols in the city were immersed in Daya and Kuakhai rivers on Sunday, the post-immersion scenario remained a matter of concern as no fully-guarded measures were taken to check waters of the rivers from getting polluted. Sources said the concerned authorities had not taken care to see that the idols made in compliance with the water pollutions norms that bar use of harmful chemicals and other stuff which cause increase in the biochemical oxygen demand (BOD) level in the river water. Even though the puja committees had not used plaster of paris (POP) and had used straw and clay in the making of idols, the harmful colours used in them are likely to affect the river waters, said a Odisha State Pollution Control Board (OSPCB) official. The huge quantity of non-biodegradable materials like chemical paints, plastic covers, jari and thermocol used in Medhas and other decorative pieces are dumped into the river along with the idols, thus causing water pollution in a big way, he pointed out. The OSPCB guidelines state that urban local bodies should be well prepared to remove all idols from the rivers within 48 hours of the immersion. The guidelines also prevent use of baked clay, toxic and non-degradable chemical and materials and removal of artificial objects like flowers, clothes and decorative materials before the immersion of the idols, the official informed. The annual average BOD level in rivers here was found to be a whopping 12.4 mg per litre as against the tolerance limit of less than 1 mg per litre. The pollution levels are alarming. There were a total of 167 puja pandals in the capital city this year which included 57 of ‘A’ category, 65 ‘B’ and 47 of ‘C’ category.