Final answer:
Leukopenia is caused by toxins that affect the bone marrow, leading to a reduction in white blood cell production, especially granulocytes, which are a type of leukocyte.
Step-by-step explanation:
The etiology of Leukopenia, which involves toxins, impacts the bone marrow. The bone marrow is crucial for hematopoiesis, the process by which all types of blood cells are formed, including leukocytes. When toxins affect the bone marrow, they can disrupt the production of leukocytes, resulting in Leukopenia. It's important to note that granulocytes, which are a type of leukocyte, are primarily affected in Leukopenia.