How does a claimant prove exposure to silica in the performance of duty?

§ 30.221 How does a claimant prove exposure to silica in the performance of duty? (a) Proof of the employee's employment and presence for the requisite days during the mining of tunnels at a DOE facility located in Nevada or Alaska for tests or experiments related to an atomic weapon may be made by the submission of any trustworthy records that, on their face or in conjunction with other such records, establish that the employee was so employed and present at these sites and the time period(s) of such employment and presence. (b) If the evidence shows that exposure occurred while the employee was employed and present at a facility during a time frame that is outside the relevant time frame indicated for that facility, OWCP may request that DOE provide additional information on the facility. OWCP will determine whether the evidence of record supports enlarging the relevant time frame for that facility. (c) Records from the following sources may be considered as evidence for purposes of establishing proof of employment or presence at a covered facility: (1) Records or documents created by any federal government agency (including verified information submitted for security clearance), any tribal government, or any state, county, city or local government office, agency, department, board or other entity, or other public agency or office. (2) Records or documents created as a byproduct of any regularly conducted business activity or by an entity that acted as a contractor or subcontractor to the DOE. (d) For purposes of satisfying the 250 workday requirement of § 30.220(a), the claimant may aggregate the days of service at more than one qualifying site.