In most cases, doctors do not know the cause of aplastic anemia. In about 20% of patients, the disease develops from an inherited disorder, such as Fanconi anemia. Aplastic anemia may also be caused by high doses of radiation or certain chemicals or viruses. There is evidence that in many people aplastic anemia is an autoimmune disease. This means that the body’s immune system is reacting against itself. The immune system attacks the bone marrow and stops it from making enough blood cells.
Is it the doctor saying that the cause is exhaust gases, or you? I would think its very unusual for a doctor to make this comment as in most cases there is no way of telling!;