Tiruvannamalai: A group of three non-governmental organisations hosted a discussion on environment pollution here on Saturday. Tamil Nadu Environment Council Secretary S.K. Vinayagam welcomed the gathering. Advocate Muthaiyan insisted that a new rule should be introduced to make it mandatory to industries to plant saplings in some areas to get clearance for their upcoming units. Government Arts College lecturer S. Kamalakannan explained the ill effects of global warming.