Final answer:
Initial symptoms of acute radiation syndrome include leukopenia and nausea and vomiting, due to the sensitivity of rapidly dividing cells to radiation; cataracts are a long-term effect.
Step-by-step explanation:
The early symptoms of acute radiation syndrome (ARS) include a series of health effects due to exposure to high levels of radiation. These symptoms arise because radiation has significant impacts on various cellular processes, especially in cells that reproduce quickly. Among the early signs are leukopenia, which is a decrease in white blood cell count, making the immune system weaker and the body more prone to infections. Another early symptom includes nausea and vomiting, which result from the damage of the cells lining the digestive system. These symptoms can occur because these cells also rapidly divide and are therefore sensitive to radiation. While cataracts can eventually form due to radiation exposure, they are not considered an immediate effect of ARS but more of a long-term consequence.