How does ionizing radiation primarily damage biological tissues?

Ionizing radiation primarily damages biological tissues by causing breakage in DNA. DNA is the fundamental molecule that carries genetic information in cells, and when ionizing radiation interacts with biological tissues, it has sufficient energy to displace electrons from atoms, leading to ionization. This process can create free radicals and charged particles, which can then directly or indirectly cause the breakage of the DNA strands.

When DNA is damaged, it can lead to mutations, cell death, or malfunction, which are critical factors in radiation's impact on biological systems, including the development of cancer and other radiation-related injuries. The repair mechanisms within cells can sometimes correct this damage, but if the damage is too extensive or occurs in critical areas of the DNA, it may result in significant biological consequences.

The other choices do not accurately depict the primary effect of ionizing radiation. For instance, promoting cell growth and enhancing cellular health are contrary to the effects observed with exposure to ionizing radiation, as it typically leads to cell death or dysfunction rather than promoting health. Altering atomic structures can occur but is not the primary mechanism by which biological damage is manifested; the breaking of DNA is more directly harmful and pertinent to radiation biology.