The apex court termed as "astonishing" that the board has not conducted a study or prepared a report on this aspect and said that government authorities have paid "very little or no attention" to the possible health hazards faced by children due to exposure to such chemicals.

It said these authorities need to realise their responsibility regarding the care and protection of health of the people in Delhi and the national capital region (NCR) and the importance of launching a sustained campaign to reduce air pollution to manageable limits during and after Diwali.

"What has really disturbed us is that the CPCB was directed on November 11, 2016 to study and prepare a report within three months on the harmful effects of the materials used in the manufacture of fireworks.

"It is astonishing that the CPCB has not conducted the study and prepared a report as directed," a bench comprising Justices Madan B Lokur and Deepak Gupta said, adding "the right to breathe clean air is a recognised right under our Constitution".

The top court, which temporarily lifted its earlier order suspending permanent licences for sale of fire crackers in the NCR, said no standards have been laid down by the CPCB which could give any indication of acceptable and permissible limit of constituent metals or chemicals used in fire crackers and released in air, beyond which their presence would be harmful.

"What is also worrying, apart from the absence of standards or limits having been laid down by the CPCB, is that very little or no attention seems to have been paid by any of the governmental authorities to the possible health hazards faced by children due to exposure to chemicals in fireworks," the bench said.

"The governmental authorities need to realise their responsibility regarding the care and protection of the health of the people in Delhi and NCR and the importance of launching a sustained campaign to reduce air pollution to manageable limits during Diwali and the period immediately thereafter.

The health of children should be of foremost concern in this regard," it said.

The bench also observed that presence of certain metals or chemicals in the air beyond a particular limit would be inadvisable, but that limit is not known to anybody including the CPCB.

"Therefore, any discussion on the subject of whether there is an excessive presence of a particular chemical in the air will not yield any result unless some authority lays down an acceptable standard of what is excessive and what is not," it said.

While temporarily lifting its earlier order, the top court said continuing the suspension of licences "might be too radical a step to take for the present" and a graded and balanced approach was needed to reduce and gradually eliminate air pollution in Delhi-NCR caused by bursting of fireworks.