Final answer:
The PHN at a nuclear accident site should monitor for leukemia, thyroid disease, and mental illness, as these conditions are known to have associations with radiation exposure.
Step-by-step explanation:
A Public Health Nurse (PHN) sent to the site of a nuclear accident for long-term surveillance would want to monitor cases of certain diseases that are likely to be related to radiation exposure. Based on the research and knowledge about nuclear accidents and their long-term health effects, the PHN would likely focus on monitoring cases of leukemia, thyroid disease, and mental illness.
Leukemia is a well-documented consequence of significant radiation exposure, such as that experienced by workers in nuclear accidents. Thyroid disease, particularly thyroid cancer, is also associated with radiation exposure, and monitoring for it is imperative as it can be a more immediate consequence after exposure to radioactive iodine. Mental illness is also an essential aspect of the surveillance due to the potential psychological impact of such disasters on the affected populations. While heart disease and diabetes are chronic noninfectious diseases found in higher rates in developed countries and linked to lifestyle and genetic factors, they are not directly associated with radiation exposure like leukemia and thyroid diseases are.