The pollutants emitted by jet aeroplanes in the outer atmosphere,such as fluorocarbons,are known as:

If the concentration of lead in the blood reaches ........,it is considered a warning sign.

Which of the following statements is $NOT$ true for aerosols?

The higher the $BOD$ of waste water,the higher is the amount of .......... in it.

According to the Central Pollution Control Board $(CPCB)$,particulate matter of what size is responsible for causing the greatest harm to human health?

Euro $II$ norms stipulate that sulphur be controlled at . . . . . . $ppm$ in diesel and . . . . . . $ppm$ in petrol.