yenvironmental media will include contributions from all sources. Neither the public healthassessment nor the health consultation attempted to discern the specific source of nickel inany media. The objective in these contaminant evaluations is to determine if the totalexposures result in doses of public health concern. If the doses are at concentrations of publichealth concern, it may become necessary to determine the specific sources in order toimplement a dose reduction strategy.
The annual smelter nickel emissions for the years 1983 to 1986 is estimated to be about 794pounds per year (based on an instantaneous emission rate of 0.05 g/sec for 8 hours per dayand 250 days per year). This operating schedule is in agreement with estimates of annualsmelter production of 6.7 million pounds per year (for the radiologically contaminatednickel). Using an average smelter loading rate of 3350 pounds per hour for 8 hours day, 250days per year equals a smelter output of 6.7 million pounds per year which is very close tothe average annual nickel production. It is assumed that releases of non-contaminated andcontaminated nickel are similar even though the maximum amount of non-contaminatednickel produced was stated to be just over 5 million pounds per year.
Although ATSDR was aware that metal smelting operations had taken place at PGDP, wehad not included such emissions in the Public Comment Release of the Public HealthAssessment. This consultation (this appendix) is a response to comments received.
ATSDR Response: Nickel stripping operations in C-400-C consisted primarily in use oforganic solvents (either trichloroethylene or trichloroethane) to remove surfacecontamination from nickel components. This process will not result in the release ofsignificant quantities of nickel. Emissions of and potential exposures to the organic solventswere evaluated in the PHA.
ATSDR Response: Any such health data is confidential information. ATSDR has no accessto such data unless provided by the individual in question and cannot review or evaluatewithout such access.
ATSDR Response: We have reconfigured the ISC air dispersion model to include potentialcontributions from both PGDP steam plant and the TVA facility. Based on 1998 and 1999Toxic Release Inventory data for the TVA facility , the instantaneous nickel air emissionsaverage ~0.0025 g/sec. Assuming that those later years are similar to the years of PGDPnickel smelter emissions, the instantaneous TVA release is about 20 times lower than thePGDP smelter release (0.05 g/sec) and is dispersed from an 800+ foot stack. Similarly,using standard emission factors for coal and oil combustion and annual fuel usage rates,instantaneous nickel emissions from the PGDP steam plant averaged 0.00009 g/sec(dispersed from two adjacent 110 foot stacks), which is 500 times lower than the smelteremissions. The results of the revised air dispersion models indicate no differences in the shortterm or annual distributions of nickel. All estimated concentrations are still well below levels of health concern.
While the revised air model does not include potential re-suspension from roadways,particulates from road dust are relatively large particles with limited capacity for widespreaddispersion. Additionally, exposure to road dust within the non-residential WKWMAroadways would be a relatively infrequent type of exposure. As a result of the limitedcapacity for significant dispersion and the infrequent exposure, nickel in road dust alongWKWMA roadways is not an important contributor to the total airborne nickel load.
ATSDR Response: While this comment is theoretically true, based on availabledocumentation, particulates from the smelter are much larger than those from the PGDPsteam plant and TVA facilities and much more likely to settle out in a short distance fromthe release point. Conversely, the smaller particle sizes from the fossil fuel facilities andmuch higher release points (stack heights), which leads to longer suspension times, meansthat nickel from those sources is dispersed over a much larger area and does not si