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G: Review of AEHA Risk Assessment Reports on Zinc Cadmium Sulfide
Pages 315-333

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From page 316...
... The Army recognizes that there was a large degree of uncertainty associated with its estimates of human health risk, as in any risk assessment, and that the calculated estimates should be taken not as "absolute estimates of risk but rather as conditional estimates." The subcommittee's evaluation of the Army Environmental Hygiene Agency (AEHA) reports on risk assessment of ZnCdS is as follows.
From page 317...
... Because zinc is an essential element for humans and animals and is generally considered to be relatively nontoxic in small amounts, the subcommittee concluded that the Army's approach of estimating the toxic potential of ZnCdS by using toxicity data on cadmium compounds as a surrogate was appropriate and could be considered to be conservative and prudent and to constitute a worst-case scenario for estimating risk associated with exposure to ZnCdS.
From page 318...
... The tracer was released at an altitude of 500 ft in all experiments except for tests 15 and 17, whose release altitudes were 750 and 1,000 ft. Rotorod samplers were placed at I-mile intervals along a 25-mile-Iong line downwind of and perpendicular to the line source at its midpoint.
From page 319...
... Some 250 Rotorod samplers were used to collect integrated samples along 5 lines across the city: ~ at the upwind edge of the city, ~ at the downwind edge, and 3 dividing the city according to major land-use categories. The 50 samplers in each line were spaced as evenly as possible.
From page 320...
... However, the same sampling rate as that used in earlier Dallas Tower experiments, 33 1:/min, was used in the calculations for determining ZnCdS concentrations in Corpus Christi because sampling rates determined at Corpus Christi were variable and on the average were not distinguishably different from the Dallas sampling rate (Smith and Wolf 1963~. The highest ZnCclS concentration was observed at the sampling station closest to the source.
From page 321...
... MINNEAPOLIS Unlike the Corpus Christi study, the Minneapolis experiments varied in sources and receptor locations from test to test. The methods used to analyze concentration data for the Minneapolis experiments are described briefly in the Army risk assessment (AEHA ~ 994b)
From page 322...
... . The risk assessment states that the maximal integrated concentration obtained outside the Clinton School was 247 particle-min/~; this value was used to represent exposure at the Clinton School.
From page 323...
... The mean of these, T.385 x 10~° particles/g, was used for converting count to weight units when the sum of the yellow and green ZnCdS concentrations was used. The Army calculated the I-h and chronic concentrations by dividing the integrated concentrations, shown in Table G-2, by the corresponding sampling times and particles-per-gram values.
From page 324...
... The average concentration in terms of weight of cadmium per volume of air was calculated by multiplying by 0.2, the Army's assumed weight fraction of cadmium in ZnCdS. TABLE G-2 Army Estimates of Time-Averaged Concentrations for Fort Wayne, IN, Atmospheric Tracer Experiments (AEHA 1995)
From page 325...
... For the pathway of direct atmospheric convection and inhalation, Table G-4 summarizes maximal integrated exposures in the 4 cities considered in this report. in Corpus Christi, the maximal integrated concentration
From page 326...
... The maximal integrated-exposure estimate was taken as the sum of the integrated concentrations at that monitoring station. TABLE G-4 Maximal Integrated Exposures and Lung Deposition of Cadmium by Direct Atmospheric Convection and Inhalation Pathway Maximal Integrated Lung Exposure Cadmium Deposition City Area (particle- min/L)
From page 327...
... The maximal integrated exposure was then converted from particle-minutes per liter to cadmium in milligram-minutes per cubic meter by using the adjustments mentioned above. Using the data from Corpus Christi as an example: 2327 part-mint g FP 103L 103 mg 0.156 mg Cd.
From page 328...
... Furthermore, it is pointed out that lung injury caused by inhalation of high concentrations of cadmium compounds, as seen in experimental animals, can range from signs of acute diffuse alveolar damage, with accompanying edema and regenerative changes during the recovery phase, to chronic degenerative lesions. Acute exposure to high concentrations of cadmium have caused death in humans, but no data are known on adverse pulmonary effects in humans exposed chronically to low concentrations.
From page 329...
... The subcommittee agrees that because of the low concentrations and short duration of the exposure, the ZnCdS tests posed negligible pulmonary-health threats to the residents in the test areas. With those considerations, the Army's health risk assessment is reasonable.
From page 330...
... The executive summaries for Corpus Christi and Minneapolis state that there are no adverse reproductive outcomes among women occupationally exposed to higher concentrations of cadmium for longer periods. Later, in the toxicity-assessment sections, the Army notes that reductions in birthweight among offspring born to exposed women were observed in 2 studies.
From page 331...
... The general approach used was that of the Environmental Protection Agency, namely, the lifetime cancer risk was calculated as the product of cancer potency and average lifetime daily dose. Because the potency was calculated to represent an upper bound for low-dose cancerrisk estimation, cancer risk < ~ ~ x \ potency / average ( daily dose )
From page 332...
... Wayne estimates by a factor of 3s x 52 = i,820. Even with appropriate adjustments to the cancer risks calculated by the Army, the lifetime lung-cancer risks associated with the low doses of cadmium are low, arid it is unlikely that anyone in these 4 test areas developed lung cancer as a result of direct inhalation of cadmium from the airborne releases.
From page 333...
... 1988. Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Volume 8, Litium Chromate ant!


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