Citation Nr: 0115991 Decision Date: 06/12/01 Archive Date: 06/18/01 DOCKET NO. 98-11 949A ) DATE ) ) On appeal from the Department of Veterans Affairs Regional Office in Boston, Massachusetts THE ISSUE Whether new and material evidence has been received to warrant reopening a claim of entitlement to service connection for xerostomia, claimed as a result of exposure to ionizing radiation, and if so, whether service connection is warranted. REPRESENTATION Appellant represented by: Disabled American Veterans ATTORNEY FOR THE BOARD C. L. Krasinski, Counsel INTRODUCTION The veteran had active service from September 1942 to December 1946. This matter is before the Board of Veterans' Appeals (the Board) on appeal from a rating decision dated in June 1998 of the Department of Veterans Affairs (VA) Regional Office in Boston, Massachusetts, (the RO) which determined that new and material evidence had not been submitted to reopen the claim for service connection for a dry mouth disorder. Review of the record reveals that service connection for a dry mouth disorder secondary to exposure to ionizing radiation had been previously denied by the RO in July 1994. The veteran was notified of this decision in July 1994 and did not file a timely appeal. Thus, this decision became final. 38 U.S.C.A. § 7105 (West 1991); 38 C.F.R. § 20.1103 (2000). In November 1999, the RO determined that the veteran had submitted new and material evidence in support of his claim to reopen the claim for service connection for xerostomia (dry mouth) as a result of radiation exposure. The RO then adjudicated the claim for service connection on a de novo basis and determined that service connection for xerostomia as a result of exposure to ionizing radiation was not warranted. The Board is, however, required to consider the issue of finality prior to any consideration on the merits and has done so herein. 38 U.S.C.A. §§ 7104(b), 5108 (West 1991); see Barnett v. Brown, 8 Vet. App. 1 (1995). The Board concludes that the veteran is not prejudiced by such an action in that the veteran's claim is herein reopened and then considered de novo on the merits. See Barnett, supra at 4; Bernard v. Brown, 4 Vet. App. 384, 390-92 (1993). The Board further notes that the veteran has withdrawn his request for a hearing before a member of the Board. See 38 C.F.R. §§ 20.702, 20.704 (2000). FINDINGS OF FACT 1. The RO denied service connection for a dry mouth disorder secondary to exposure to ionizing radiation in July 1994 and notified the veteran of the decision; he did not appeal. 2. The evidence submitted subsequent to the July 1994 RO decision includes that which bears directly and substantially upon the specific matter under consideration; is not cumulative; and is so significant that it must be considered in order to fairly decide the merits of the claim. 3. The veteran was a member of the American occupation forces in Japan following World War II, had service aboard the U.S.S. LSM 7, and was present in the Hiroshima area from November 28 to December 4, 1945. 4. The veteran's exposure to radiation in service was one rem. 5. The competent and probative medical evidence of record indicates that xerostomia was not present in service and was first manifested nearly 44 years after the veteran's in- service exposure to ionizing radiation; the evidence does not establish a relationship between xerostomia and the veteran's period of service, to include his exposure to ionizing radiation. CONCLUSIONS OF LAW 1. New and material evidence has been received to reopen the claim of entitlement to service connection for xerostomia. 38 U.S.C.A. § 5108; 38 C.F.R. § 3.156(a) (2000). 2. Xerostomia was not incurred in or aggravated by active service and may not be presumed to have been incurred in active service. 38 U.S.C.A. §§ 1101, 1110, 1112, 1113 (West 1991); Veterans Claims Assistance Act of 2000 (VCAA), Pub. L. No. 106-475, § 4, 114 Stat. 2096, 2098-99 (2000) (to be codified as amended at 38 U.S.C. § 5107); 38 C.F.R. §§ 3.303, 3.307, 3.309, 3.311 (2000). REASONS AND BASES FOR FINDINGS AND CONCLUSIONS Pertinent Law and Regulations In order to establish service connection for a disability, the evidence must demonstrate the presence of it and that it resulted from disease or injury incurred in or aggravated by service. 38 U.S.C.A. § 1110; 38 C.F.R. § 3.303. Service connection may also be granted for a disease first diagnosed after discharge when all of the evidence, including that pertinent to service, establishes that the disease was incurred in service. 38 C.F.R. § 3.303(d). Service connection for disability that is claimed to be attributable to exposure to ionizing radiation during service can be demonstrated by three different methods. See Rucker v. Brown, 10 Vet. App. 67, 71 (1997). First, there are certain types of cancer that are presumptively service connected specific to radiation-exposed veterans. 38 U.S.C.A. § 1112(c); 38 C.F.R. § 3.309(d). Second, "radiogenic diseases" may be service connected pursuant to 38 C.F.R. § 3.311. Third, service connection may be granted under 38 C.F.R. § 3.303(d) when it is established that the disease diagnosed after discharge is the result of exposure to ionizing radiation during active service. See Combee v. Brown, 34 F.3d 1039 (Fed. Cir. 1994). The provisions of 38 C.F.R. § 3.309 provide that if a veteran, while on active duty, active duty for training, or inactive duty training, participated in a radiation-risk activity, as defined by regulation, the following diseases shall be service connected, even though there is no record of such disease during service, provided further that the rebuttable presumption provisions of 38 C.F.R. § 3.307 are also satisfied: Leukemia (other than chronic lymphocytic leukemia); cancers of the thyroid, breast, pharynx, esophagus, stomach, small intestine, pancreas, bile ducts, gall bladder, salivary gland and urinary tract; multiple myeloma; lymphomas (except Hodgkin's disease); and primary liver cancer (except if cirrhosis or hepatitis B is indicated). 38 C.F.R. § 3.309(d). "Radiation-risk activity" is defined as onsite participation in a test involving the atmospheric detonation of a nuclear device; the occupation of Hiroshima or Nagasaki, Japan, by U.S. forces during the period of time from August 6, 1945 through July 1, 1946; or internment as a prisoner of war in Japan during World War II, and/or service on active duty in Japan immediately following such internment, resulting in the opportunity for exposure to ionizing radiation comparable to that of U.S. occupation forces in Hiroshima or Nagasaki, Japan from August 6, 1945 through July 1, 1946. 38 C.F.R. § 3.309 (d)(3)(ii). 38 C.F.R. § 3.311 provides instruction on the development of claims based on exposure to ionizing radiation, and does not refer to any other types of radiation exposure. 38 C.F.R. § 3.311(a) calls for the development of a dose assessment where it is established that a radiogenic disease first became manifest after service, where it was not manifest to a compensable degree within any applicable presumptive period specified in either § 3.307 or § 3.309, and where it is contended that the disease is a result of ionizing radiation in service. 38 C.F.R. § 3.311(a)(2) requires that dose data will be requested from the Department of Defense in all claims based upon participation in the American occupation of Hiroshima or Nagasaki, Japan, prior to July 1, 1946. 38 C.F.R. § 3.311. Pursuant to 38 C.F.R. § 3.311, "radiogenic disease" is defined as a disease that may be induced by ionizing radiation, and specifically includes the following: thyroid cancer, breast cancer, lung cancer, bone cancer, liver cancer, skin cancer, esophageal cancer, stomach cancer, colon cancer, pancreatic cancer, kidney cancer, urinary bladder cancer, salivary gland cancer, multiple myeloma, posterior subcapsular cataracts, non-malignant thyroid nodular disease, ovarian cancer, parathyroid adenoma, tumors of the brain and central nervous system, cancer of the rectum, lymphomas other than Hodgkin's disease, prostate cancer, and any other cancer. 38 C.F.R. § 3.311(b)(2)(i)-(xxiv). In addition, 38 C.F.R. § 3.311 (b)(4) provides that, even if the claimed disease is not one that is already recognized as radiogenic by 38 C.F.R. § 3.311(b)(2), the claim will still be considered, or developed, under § 3.311 if the veteran cites or submits competent scientific or medical evidence that the claimed disease is radiogenic. Id. The provisions of 38 C.F.R. § 3.311 (b)(1) require that claims involving exposure to ionizing radiation will be referred to the VA Undersecretary for Benefits if it is determined that: (1) a veteran was exposed to ionizing radiation; (2) the veteran subsequently developed a radiogenic disease; and (3) such disease became manifest within the period specified in 38 C.F.R. § 3.311(b)(5)(2 ). Id. Factors to be considered in determining whether a veteran's disease resulted from exposure to ionizing radiation in service include: (1) The probable dose, in terms of dose type, rate and duration as a factor in inducing the disease, taking into account any known limitations in the dosimetry devices employed in its measurement or the methodologies employed in its estimation; (2) The relative sensitivity of the involved tissue to induction, by ionizing radiation, of the specific pathology; (3) The veteran's gender and pertinent family history; (4) The veteran's age at time of exposure; (5) The time-lapse between exposure and onset of the disease; and (6) The extent to which exposure to radiation, or other carcinogens, outside of service may have contributed to development of the disease. 38 C.F.R. § 3.311 (e). Factual Background Service medical records show that upon enlistment examination in September 1942, examination of the veteran's mouth and glands were normal. The service separation examination report, dated in November 1946, indicates that examination of the veteran's tongue, palate, and glands was normal. The service medical records are silent for complaints or diagnosis of xerostomia. A May 1976 VA examination report was silent for complaints of dry mouth or diagnosis of xerostomia. A VA treatment record dated in 1993 reflects complaints of dry mouth. In a September 1993 statement, the veteran indicated that he had radiation problems that he thought came from World War II. He stated that he had no saliva in his mouth. In a decision dated in July 1994, the RO denied service connection for dry mouth, claimed as secondary to exposure to ionizing radiation and notified the veteran of the decision. He did not appeal. In an October 1997 statement, the veteran stated that he had a dry mouth condition due to radiation exposure while stationed at Hiroshima and Nagasaki in 1945. He stated that he was seen at T. University for this condition. He indicated that he was told that there was nothing that could be done. In a May 1998 statement, Dr. A.P. of the T. University School of Dental Medicine, Oral Medicine Service, stated that the veteran was examined in May 1998. Dr. A.P. indicated that the veteran had a low salivary flow, unstimulated whole saliva which equaled zero and stimulated whole saliva which equaled 0.4 ml/min. Dr. A.P. stated that this was comparable to radiation people who have a mean stimulated flow of 0.7 ml/min and unstimulated flow of 0.03 ml/min. Dr. A.P. stated that medication-induced xerostomia had a higher stimulated flow with the mean of 1.23 ml/min. Dr. A.P. noted that the veteran was seen seven years ago before he was on xerostomia medication and at that time, he was severely xerostomia without taking medication. Dr. A.P. concluded that the veteran had a radiation induced xerostomia resulting from his exposure to radiation during World War II. In July 1998, the RO contacted the Defense Nuclear Agency and requested confirmation of the veteran's presence and nature of his duties at the nuclear test or occupation of Hiroshima or Nagasaki. The RO requested the Defense Nuclear Agency to provide the recorded levels of radiation exposure for the veteran's unit of assignment. In an August 5, 1998 letter to the RO, the Nuclear Test Personnel Review indicated that they were researching the veteran's case. In August 1998, the National Personnel Records Center (NPRC) submitted an abstract of service which indicated that the veteran served on the USS LSM 7 from November 9, 1945 to January 17, 1946. In an August 1998 follow-up letter, the Nuclear Test Personnel Review of the Defense Special Weapons Agency, indicated that naval records confirmed that the veteran was a member of the American occupation forces in Japan following World War II. The Nuclear Test Personnel Review indicated that while serving aboard USS LSM 7, the veteran was present in the VA-defined Hiroshima area from November 28 to December 4, 1945. The Nuclear Test Personnel Review indicated that the scientific dose reconstruction titled Radiation Dose Reconstruction U.S. Occupation Forces in Hiroshima and Nagasaki, Japan, 1945-1946 (DNA 5512F) determined the maximum possible radiation dose that might have been received by any individual who was at either Hiroshima or Nagasaki for the full duration of the American occupation (September 1945 to June 1946 for Nagasaki; and September 1945 to March 1946 for Hiroshima). The Nuclear Test Personnel Review stated that using all possible "worst case" assumptions, the maximum possible dose any individual serviceman might have received from external radiation, inhalation, and ingestion was less than one rem. This did not mean that any individual approached that level of exposure. The Nuclear Test Personnel Review stated that in fact, it was probable that the great majority of servicemen assigned to the Hiroshima and Nagasaki occupation forces received no radiation exposure whatsoever, and that the highest dose received by anyone was a few tens of millirem. In July 1999, the RO referred the veteran's radiation claim to the Compensation and Pension Service for review under the provisions of 38 C.F.R. § 3.311 (b)(1)(ii). In September 1999, the Director of Compensation and Pension requested the Under Secretary for Health to render an opinion as to whether it was likely, unlikely, or at least as likely as not that the xerostomia resulted from exposure to ionizing radiation in service. In an October 1999 letter, the VA Chief Public Health and Environmental Hazards Officer, Dr. S.M., indicated that they were responding to the memorandum dated in September 1999. Dr. S.M. stated that the Defense Special Weapons Agency estimated that the veteran was exposed to a dose of ionizing radiation during military service of less than 1 rem. Dr. S.M. noted that the Committee on Interagency Radiation Research and Policy Coordination (CIRRPC) Science Panel Report Number 6,1988, did not provide screening doses for xerostomia (dry mouth). Damage to the salivary glands other than neoplastic transformation, if caused by radiation, would be an example of a deterministic effect. Deterministic changes generally were considered to have a threshold. Dr. S.M. indicated that the probability of causing harm in most healthy individuals at doses of less than 10 rem as a result of deterministic effects was close to zero (Institute of Medicine Report, Adverse Reproductive Outcomes in Families of Atomic Veterans: The Feasibility of Epidemiologic Studies, 1995, pages 23-24). Dr. S.M. indicated that Xerostomia can follow high-dose radiation therapy (e.g., hundreds or thousands of rads) (Mettler and Upton, Medical Effects of Ionizing Radiation, 2nd edition, 1995, pages 235-236). In light of the above, Dr. S.M. concluded that it was unlikely that the veteran's xerostomia could be attributed to exposure to ionizing radiation in service. In an October 1999 letter, the Director of Compensation and Pension Service indicated that they received the medical opinion from the Under Secretary for Health which advised that it was unlikely that the veteran's xerostomia resulted from his exposure to ionizing radiation in service. As a result of this opinion, and following review of the evidence in its entirety, the Director of Compensation and Pension Service concluded that there was no reasonable possibility that the veteran's disability was the result of such exposure. Analysis Initial Matters During the pendency of the veteran's appeal the VCAA, Pub. L. No. 106-475, 114 Stat. 2096 (2000) was signed into law. This liberalizing legislation is applicable to the veteran's claim. See Karnas v. Derwinski, 1 Vet. App. 308, 312-13 (1991). It essentially eliminates the requirement that a claimant submit evidence of a well-grounded claim, and provides that VA will assist a claimant in obtaining evidence necessary to substantiate a claim but is not required to provide assistance to a claimant if there is no reasonable possibility that such assistance would aid in substantiating the claim. It also includes new notification provisions. Specifically, it requires VA to notify the claimant and the claimant's representative, if any, of any information, and any medical or lay evidence, not previously provided to the Secretary that is necessary to substantiate the claim. As part of the notice, VA is to specifically inform the claimant of which portion, if any, of the evidence is to be provided by the claimant and which part, if any, VA will attempt to obtain on behalf of the claimant. The Board finds that the veteran is not prejudiced by its consideration of his claim pursuant to this new legislation insofar the requirements of the VCAA have been satisfied with respect to the issue on appeal. There is sufficient evidence of record with which the Board may make an informed decision. The Board has not identified any pertinent evidence which is not currently of record, and the veteran has not pointed to any such evidence. The Board points out that the RO developed the veteran's claim pursuant to the provisions of 38 C.F.R. § 3.311. Review of the record reveals that the RO contacted the Defense Nuclear Agency in July 1998 and requested confirmation that the veteran participated in radiation-risk activity, as the veteran claimed. The RO also requested the veteran's radiation dose information. In August 1998, the Nuclear Test Personnel Review provided the RO with the requested information. In July 1999, the RO referred the veteran's claim to the Director of Compensation and Pension for consideration pursuant to 38 C.F.R. § 3.311. In September 1999, the Director of Compensation and Pension referred the claim to the VA Under Secretary for Health for an opinion as to whether the veteran's disability resulted from exposure to radiation. The Under Secretary for Health considered the evidence and rendered a medical opinion. Thus, the Board finds that the RO properly developed the veteran's claim pursuant to 38 C.F.R. § 3.311. The Board acknowledges argument put forth by the veteran's representative to the effect that T. University has indicated only that records were unidentifiable in that VA had used the veteran's initials and not his full name. However, the claims file contains a summary opinion from Dr. A.P., associated with T. University. Dr. A.P. is the physician who reportedly treated the veteran and the opinion presented is favorable to the veteran. Such opinion has been considered herein. The Board further observes that in the July 1998 statement of the case and the November 1999 supplemental statement of the case, the veteran was informed of the pertinent law and regulations and was notified of the evidence needed to be shown in order for his claim to be granted. The veteran has been accorded ample opportunity to present evidence and argument in support of this claim and has neither submitted nor identified additional relevant evidence. When the Board addresses in its decision a question that has not been addressed by the RO, it must consider whether the appellant has been given adequate notice to respond and, if not, whether he has been prejudiced thereby. See Bernard v. Brown, 4 Vet. App. 384 (1993). In the present case, the veteran's claim has been adjudicated by the RO under the same statutory and regulatory criteria which must be applied by the Board. Accordingly, the Board does not believe that a remand for re-adjudication is required under the VCAA or otherwise. In short, the Board has carefully considered the provisions of the VCAA in light of the record on appeal, and for the reasons expressed above finds that the development of this claim has been consistent with the provisions of the new law. Under these circumstances, a remand of this matter for further development would not avail the veteran or aid the Board's inquiry, and would only serve to unnecessarily delay a decision. See Soyini v. Derwinski, 1 Vet. App. 540, 546 (1991). Discussion-Finality As the veteran did not appeal the July 1994 RO decision, see 38 C.F.R. §§ 20.200, 20.302 (2000), such became final. 38 U.S.C.A. § 7105(c) (West 1991); 38 C.F.R. § 20.1103 (2000). A final and binding decision shall not be subject to revision on the same factual basis except as provided by regulation. See 38 C.F.R. § 3.105 (2000). However, if new and material evidence is presented or secured with respect to a claim that has been disallowed, the Secretary shall reopen the claim and review the former disposition of the claim. 38 U.S.C.A. § 5108; Hickson v. West, 12 Vet. App. 247 (1999). New and material evidence is defined as evidence not previously submitted to agency decisionmakers which bears directly and substantially upon the specific matter under consideration; which is neither cumulative nor redundant; and which, by itself or in connection with evidence previously assembled, is so significant that it must be considered in order to fairly decide the merits of the claim. 38 C.F.R. § 3.156(a). In Hodge v. West, 155 F.3d 1356, 1363 (Fed. Cir. 1998), the Federal Circuit noted that new evidence could be sufficient to reopen a claim if it could contribute to a more complete picture of the circumstances surrounding the origin of a veteran's injury or disability, even where it would not be enough to convince the Board to grant a claim. In July 1994, the RO denied the claim based on the absence of a diagnosed disability related to in-service radiation exposure. Subsequent to the July 1994 RO decision, VA received an opinion from a competent physician that the veteran's clinical pathology related to dry mouth, diagnosed as xerostomia, was consistent with that seen in radiation- exposed individuals and that the veteran's xerostomia resulted from radiation exposure during World War II. Also received were records and opinions pertinent to the nature and amount of the veteran's in-service exposure to radiation. Such evidence is clearly pertinent to the matter on appeal; accordingly, the claim was properly reopened. 38 C.F.R. § 3.156(a). Discussion-Service Connection In accordance with the Court's holding in Combee, supra, the Board will first address the potential application of presumptive service connection for radiation-exposed veterans pursuant to 38 C.F.R. § 3.309(d). The Board will then address the relevance of the "radiogenic diseases" provisions of 38 C.F.R. § 3.311. Lastly, the Board will discuss whether service connection has been established by way of proof of actual direct causation under 38 C.F.R. § 3.303(d). See Combee, 34 F.3d at 1043-1044. Presumptive service connection - radiation exposure Initially, the Board finds that the evidence of record does establish that the veteran is a radiation-exposed veteran as defined by 38 C.F.R. § 3.309(d)(3)(i). The Nuclear Test Personnel Review indicated that naval records confirmed that the veteran was a member of the American occupational forces in Japan following World War II; he served aboard the U.S.S. LSM 7; and he was present in the Hiroshima area from November 28 to December 4, 1945. This evidence establishes that the veteran participated in "radiation-risk activity" as defined by 38 C.F.R. § 3.309(d)(3), and therefore, he is considered a radiation-exposed veteran. However, status as a radiation-exposed veteran is not sufficient, by itself, to warrant presumptive service connection under the provisions of 38 C.F.R. § 3.309. Rather, in order to warrant such a presumption, the veteran must be diagnosed with one of the presumptive diseases specifically listed under 38 C.F.R. § 3.309(d)(2). The medical evidence of record establishes that the veteran has xerostomia. In the May 1998 statement, Dr. A.P. of the T. University School of Dental Medicine, Oral Medicine Service, stated that the veteran was examined in May 1998 and he had xerostomia. The evidence of record shows that the xerostomia first manifested in the early 1990's. In the May 1998 statement, Dr. A.P. noted that the veteran was seen seven years ago before he was on xerostomia medication and at that time, he was severely xerostomia without taking medication. Xerostomia is not specified as one of the disabilities presumed to be related to exposure to radiation pursuant to 38 C.F.R. §§ 3.307 and 3.309. Accordingly, service connection for xerostomia cannot be granted on a presumptive basis. Thus, the Board can find no basis for applying the presumptive provisions of 38 C.F.R. § 3.309. The Board points out that in a June 1999 letter, the veteran indicated that he had salivary gland cancer which caused the xerostomia. The Board notes in passing that cancer of the salivary gland is listed as one of the presumptive conditions set forth in 38 C.F.R. § 3.309(d) as being related to radiation exposure. However, there is no competent medical evidence of record demonstrating that the veteran has ever been diagnosed with cancer of the salivary gland. The veteran himself is not competent to render a medial opinion as to whether he has or had cancer of the salivary glands. Although the veteran and other lay persons are competent to testify as to his in-service experiences and symptoms, where the determinative issue involves a question of medical diagnosis or causation, only individuals possessing specialized medical training and knowledge are competent to render such an opinion. Espiritu v. Derwinski, 2 Vet. App. 492 (1992). Moreover, the veteran has not filed a claim for service connection for cancer of the salivary glands and this issue is not before the Board for appellate review. In short, the disorders granted presumptive service connection under 38 C.F.R. § 3.309(d) for radiation exposure are specified with precision, and the disorder for which service connection is sought must be specified at 38 C.F.R. § 3.309(d) in order to enjoy the presumption of service incurrence thereunder. Because the veteran's xerostomia is not included among the diseases specified at 38 C.F.R. § 3.309(d), the Board finds that the veteran's claim, as evaluated under the regulations governing presumptive service connection based on radiation exposure, must be denied. Radiogenic diseases under 38 C.F.R. § 3.311 As noted above, the provisions of 38 C.F.R. § 3.311 provide for development of claims based on a contention of radiation exposure during active service and post-service development of a radiogenic disease. The provisions do not give rise to a presumption of service connection, but rather establish a procedure for handling claims brought by radiation exposed veterans or their survivors. See Ramey v. Brown, 120 F.3d 1239, 1244 (Fed. Cir. 1997). Specifically, 38 C.F.R. § 3.311(a) states that in all claims in which it is established that a radiogenic disease first became manifest after service, and it is contended that the disease resulted from radiation exposure, a dose assessment will be made. 38 C.F.R. § 3.311(b)(1) further states that if it is ultimately determined that the veteran was exposed to ionizing radiation, that the veteran subsequently developed a radiogenic disease and that such disease became manifest within the period specified in 38 C.F.R. § 3.311(b)(5)(2 ), the claim will be referred to the VA Under Secretary for Benefits. As discussed above, the RO properly developed the claim in accordance with 38 C.F.R. § 3.311. In this case, the veteran is seeking service connection for xerostomia. This disorder is not among the radiogenic diseases specified in 38 C.F.R. § 3.311(b)(2). However, the veteran has submitted medical evidence pertinent to whether xerostomia is a radiogenic disease. See 38 C.F.R. § 3.311(b)(4). In the May 1998 statement, Dr. A.P. of the T. University School of Dental Medicine, indicated, in essence, that people exposed to radiation could develop xerostomia and the veteran had radiation-induced xerostomia. Also, the evidence of record establishes that the veteran's xerostomia became manifest more than five years after exposure to radiation. The demonstration of a radiogenic disease does not, in and of itself, establish entitlement to service connection. The Board must consider all relevant factors, including the amount of radiation exposure, the veteran's age at the time of the exposure, and the time-lapse between exposure and onset, in determining whether the veteran's xerostomia was caused by exposure to ionizing radiation in service. The RO thus obtained information as to the size and assessment of the veteran's radiation dose. The Nuclear Test Personnel Review of the Defense Special Weapons Agency indicated that naval records confirmed that the veteran was present in the VA-defined Hiroshima area from November 28 to December 4, 1945. The Nuclear Test Personnel Review stated that using all possible "worst case" assumptions, the maximum possible dose any individual serviceman might have received from external radiation, inhalation, and ingestion was less than one rem. After careful review of the evidence of record, the Board finds that the xerostomia did not result from exposure to ionizing radiation in service. As noted above, Dr. S.M., the Chief Public Health and Environmental Hazards Officer, concluded that it was unlikely that the veteran's xerostomia could be attributed to the ionizing radiation in service. Dr. S.M. indicated that damage to salivary glands other than neoplastic transformation, if caused by radiation, was a deterministic effect. Dr. S.M. indicated that the probability of causing harm in most healthy individuals at doses of less than 10 rem as a result of deterministic effects was close to zero. Dr. S.M. indicated that the veteran's estimated dose of ionizing radiation was one rem. Dr. S.M. also noted that xerostomia can follow high-dose radiation therapy (e.g., hundreds or thousands of rads). Dr. S.M. cited to the scientific and medical research which supported her conclusions. The Board finds this medical opinion to be more probative that that offered by Dr. A.P. It is the Board's responsibility to assess the credibility and the probative value of proffered evidence of record in its whole. See, e.g. Madden v. Gober, 125 F. 3d 1477, 1481 (Fed. Cir. 1997); Guimond v. Brown, 6 Vet. App. 69, 72 (1993); Hensley v. Brown, 5 Vet. App. 155, 161 (1993). First, Dr. S.M. is an expert. He is the Chief Public Health and Environmental Hazards Officer. Dr. S.M. has special knowledge in the field of medical effects of ionizing radiation and is competent to render a medical opinion as to whether the veteran's xerostomia was due to the exposure to ionizing radiation in service. In evaluating the probative value of medical statements, the Board looks at factors such as the health care provider's knowledge and skill in analyzing the medical data. See Guerrieri v. Brown, 4 Vet. App. 467, 470-71 (1993); see also Black v. Brown, 10 Vet. App. 279, 284 (1997). The Board also finds the medical opinion by Dr. S.M. to be highly probative because Dr. S.M. specifically considered the veteran's estimated dose of ionizing radiation, which was one rem. Dr. S.M. also considered the specific type of disorder that the veteran alleged was due to ionizing radiation and the veteran's health at the time of exposure. The Board also points out that Dr. S.M. analyzed recent scientific studies regarding the medical effects of ionizing radiation exposure and the epidemiology of radiogenic diseases. Dr. S.M. cited to the scientific and medical research that supported her medical conclusion. The Board has carefully considered the medical opinion of Dr. A.P. Dr. A.P. essentially concluded that the veteran had radiation-induced xerostomia resulting from his exposure to radiation during World War II because his salivary flow was comparable to the salivary flow of people with radiation- induced xerostomia as compared to people with medication- induced xerostomia. The Board finds this opinion to be of less probative value than the opinion of Dr. S.M., particularly because Dr. A.P. failed to specifically address several of the factors considered by Dr. S.M. in her opinion, including, most significantly, the veteran's specific level of radiation exposure in service and the type of radiation exposure. As noted above, 38 C.F.R. § 3.311(e) specifically lists probable dose assessment as a factor to be considered in determining whether a claimed radiogenic disease is related to exposure to ionizing radiation in service. Therefore, the Board places much more probative weight on the opinion of Dr. S.M., who specifically considered the veteran's dose assessment and the type of radiation exposure, which in the veteran's case, was ionizing radiation exposure. Dr. S.M. indicated that high-dose radiation therapy could cause xerostomia. The Board notes that the veteran does not allege high-dose radiation therapy in service and the evidence of record does not establish this type of exposure. In light of the fact that Dr. S.M. considered the veteran's specific dose estimate and specific type of radiation exposure in reaching her conclusion, the Board finds her opinion to be of much more probative value than the opinion of Dr. A.P. who did not address the amount or type of the veteran's radiation exposure. Further, Dr. A.P. did not refer to any studies of radiation- exposed veterans at atomic test sites. She did not cite to any scientific or medical studies which supported her conclusion. Thus, the Board finds Dr. A.P.'s medical opinion to be unpersuasive. In summary, for the reasons and bases set forth above, the Board finds that most probative evidence of record is the opinion of Dr. S.M., who found that it was unlikely that the veteran's xerostomia was incurred as a result of exposure to ionizing radiation in service. Thus, the Board finds that the preponderance of the evidence is against the claim for service connection for xerostomia under the provisions of 38 C.F.R. § 3.311. Direct service connection Notwithstanding the foregoing, the United States Court of Appeals for the Federal Circuit has determined that the regulations governing presumptive service connection for radiation exposure do not preclude a veteran from establishing service connection with proof of actual direct causation. Combee, 34 F.3d at 1043-1044. Accordingly, the Board will proceed to evaluate the veteran's claim under the regulations governing direct service connection. At the outset, the Board notes that for the purposes of this opinion, it does not challenge the veteran's contention that he was exposed to ionizing radiation during service. As noted above, the record reflects that the veteran was a member of the American occupation forces in Japan following World War II. The Nuclear Test Personnel Review indicated that while serving aboard U.S.S. LSM 7, the veteran was present in the VA-defined Hiroshima area from November 28 to December 4, 1945. The Nuclear Test Personnel Review indicated that using all possible "worst case" assumptions, the maximum possible dose any individual serviceman might have received from external radiation, inhalation, and ingestion was less than one rem. The Board notes that there is no other evidence of record regarding the veteran's level of radiation exposure in service. Thus, for the purposes of this decision, the Board will concede that the veteran was exposed to at least some degree of ionizing radiation in service. After carefully reviewing all of the evidence of record, including the medical opinions set forth above, the Board concludes that the preponderance of the evidence is against the veteran's claim for service connection for xerostomia on a direct basis. In that regard, service medical records are silent for complaints or diagnosis of xerostomia. Also, the record shows that the xerostomia first manifested in the early 1990's, over 44 years after service separation in 1946. And, as discussed in detail above, the most probative medical evidence of record, based on complete consideration of the relevant record, establishes that it is unlikely that the veteran's xerostomia was the result of exposure to ionizing radiation in service and does not otherwise attribute such to military service. The veteran himself has asserted that he incurred xerostomia as a result of exposure to ionizing radiation in service. However, the evidence does not reflect that the veteran possesses a recognized degree of medical knowledge that would render his opinion as to the etiology of the xerostomia competent. See Espiritu v. Derwinski, 2 Vet. App. 492 (1992). There is no other probative medical evidence to support his contention, or to establish the xerostomia was first manifest during service or is otherwise related to service. In summary, for the reasons and bases expressed above the Board believes that the preponderance of the competent and probative evidence of record is against finding that the veteran's xerostomia was incurred or aggravated in service or is etiologically related to the veteran's period of service, including the exposure to ionizing radiation in service. The benefit sought on appeal is accordingly denied. ORDER The claim of entitlement to service connection for xerostomia as due to exposure to ionizing radiation is denied. J. M. Daley Acting Member, Board of Veterans' Appeals