Consider the following statements

1.    Ionizing radiation is a type of energy released by atoms in the form of electromagnetic waves or particles.

2.    People are exposed to natural sources of ionizing radiation, such as in soil, water, vegetation, and in human-made sources, such as x-rays and medical devices.

3.    Ionizing radiation has many beneficial applications, including uses in medicine, industry, agriculture and research.

4.    The sievert (Sv) is a unit of radiation weighted dose also called the effective dose. It is a way to measure ionizing radiation in terms of the potential for causing harm.

Which of the above statements are correct?