What is the term for the undesirable change in the physical,chemical,or biological characteristics of air,water,or land?

What is the density of heavy metals?

What is the consequence of a lake being saturated with organic waste?

Which of the following concentrations in the atmosphere leads to acid rain?

$A$ dental disease characterized by mottling of teeth is due to the presence of a certain chemical element in drinking water. Which is that element?

Assertion: $A$ suspended particulate matter $(SPM)$ is an important pollutant released by diesel vehicles.
Reason: Catalytic converters greatly reduce pollution caused by automobiles.