Name two main sources of nuclear radiations. How are the nuclear radiations harmful?

Two main sources of nuclear radiations are:

1. Radioactive fall out from nuclear plants — The nuclear power plants are now a major source of electricity in the world. If somehow, there is an accident in the reactor of power plant, a large amount of radioactive material and radiations will escape out into the atmosphere. This will not only affect the population around the plant, but will also affect the life at far off places where they will reach due to air currents.
2. Nuclear waste — The nuclear waste are still very radioactive and are a source of harmful radiations therefore, they should not be dumped in the open garbage. They can contaminate water and soil and affect the human and living organisms.

The harmful biological effects of nuclear radiations are of three types:

1. Short term recoverable effects like diarrhea, sore throat, loss of hair, nausea, etc.
2. Long term irrecoverable effects like leukemia and cancer.
3. Genetic effects that appear in the later generations of the person exposed to the radiation as the genes in the living cell get modified.