(a) Presumption of exposure. A covered veteran as defined in § 3.320a(c) shall be presumed to have been exposed to certain toxic substances, chemicals, and airborne hazards, including fine particulate matter, during such service, unless there is affirmative evidence to establish that the veteran was not exposed to any such toxic substances, chemicals, and airborne hazards during that service.

(b) Presumption of service connection. Except as provided in paragraph (c) of this section, the following diseases becoming manifest in a covered veteran, as defined in § 3.320a(c), shall be considered to have been incurred in or aggravated during active military, naval, air, or space service, notwithstanding that there is no record of evidence of such disease during the period of such service:

(1) Acute leukemias.

(2) Chronic leukemias.

(3) Multiple myelomas, including monoclonal gammopathy of undetermined significance (MGUS).

(4) Myelodysplastic Syndromes (MDS).

(5) Myelofibrosis.

(c) Exceptions. A disease listed in paragraph (b) of this section shall not be presumed service connected if there is affirmative evidence that:

(1) The disease was not incurred or aggravated during active military, naval, air, or space service; or

(2) The disease was caused by a supervening condition or event that occurred between the veteran's most recent departure from active military, naval, air, or space service and the onset of the disease; or

(3) The disease is the result of the veteran's own willful misconduct.