Even as the phasing out of leaded petrol in Delhi has led to jubilation among environmentalists, they are up in arms against the rising levels of benzene in Delhi's atmosphere. And the highly carcinogenic nature of "Kekule's ring" has indeed become a cause for alarm.The benzene content in Delhi's atmosphere as measured by the Central Pollution Control Board(CPCB) is many times the European Union's safety standards of 10 pppm. An independent research carried out at the ITO area of Delhi showed a benzene content of 139 pppm.