ata. However, the available data do notinclude ambient nickel analyses. Even if such data did exist, it is very unlikely that themonitor locations would have been appropriately located so as to assess the spatiallyrestricted areas affected by emissions from the nickel smelter. As our modeled ambient airconcentrations are based on measured stack concentrations and are consistent with measuredsoil concentrations, we are confident that the results of the evaluation are protective of publichealth.
ATSDR Response: According to the information available , stack concentrations weremeasured for three separate trial runs of the batch smelter using an average of 96% of themaximum charging capacity. The average annual smelter output was ~72% of the annualmaximum charging capacity. Therefore, the trial runs were conducted using conservativeestimates of operating capacity. ATSDR used an estimated instantaneous nickel emissionvalue that was 13% greater than the measured average trial run value. Overall, theseemission and production values indicate that ATSDR employed health protective estimatesof annual production and instantaneous emission rates in estimating airborne nickelconcentrations to off-site areas.
The odd thing about some of the slag was it's tendency to roll onto the surface of themelt in the form of golf ball sized spheres which were sometimes kept as souvenirs onworker's desk. A more accurate estimation of releases could be made by having thesespheres tested (they are still around, no pun intended) or better still performing amass balance (drums of flakes were weighed and sampled before and ingots weretested after they were cast so total material lost could be estimated). [redacted name]in the C-710 building closely studied distribution of materials within the meltingprocess and his documents detail his findings (a search of the database using his nameas the author should kick out some good information, e.g. K/TL 338-339-443 andK/PS230). If nothing is easily available I could provide some of the analytical resultfrom the testing done.
ATSDR Response: The Commentor is correct that radionuclide concentrations in the nickelbuttons underestimate the total radionuclide concentration of the feed material due tosegregation in the slag and nickel ingots. However, as stated in the above response to item 1,radionuclide stack emissions were also directly measured. Annual emissions from the C-746A stack are reported for the calender year 1985 . As these values are all at least fiveorders of magnitude lower than the emissions from other previously evaluated sources forearlier years (1956-59), they do not comprise a significant additional source of radionuclideemissions (see Table E-1 in Apendix E for uranium values evaluated for specific releaseyears).
ATSDR Response: The section containing the cited paragraph is entitled "Evaluation ofModeled Concentrations of Airborne Metals Particulates." While this clearly indicates thatthe data in question are model results, we will add the term "modeled" or "estimated" to thecited sentences. The comment is not correct in stating that "better data" are available whichshould be demanded from DOE. As historic off-site airborne nickel concentrations were notcollected for the express purpose of quantifying potential off-site exposures, any additionaldata will be subject to inherent uncertainty which limits its utility for exposure assessment.The best response to such uncertainty is to seek consistency from different types of data.Because our modeled off-site concentrations are based on measured stack concentrations andare consistent with measured soil concentrations, we are confident that the results of theevaluation are protective of public health.
ATSDR Response: The suggested revision has been incorporated into the healthconsultation. It is important to note the distinction between emissions from primary andsecondary (such as PGDP) nickel smelting operations. More than 90% of emissions fromsecondary smelters are in an oxide form . Refinery dust (primarily nickel subsulfide) ismore typically produ