Toxicologic Assessment of the Army's Zinc Cadmium Sulfide Dispersion Tests (1997) / Chapter Skim
Currently Skimming:
Risk Characterization of Exposures to Zinc Cadmium Sulfide
Risk Characterization of Exposures to Zinc Cadmium Sulfide
Pages 67-81
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 67... ...
A ~ 994 NRC report describes a 4-step analytic process for performing a human-health risk assessment, which involves hazard identification, dose-response assessment, exposure assessment, and risk characterization. When a substance leaves a source (such as an industrial facility)
|
From page 68... ...
Results of the subcommittee's analyses can be found in Chapters 2, "Input from the Public"; 3, "Toxicity and Related Data on Zinc Cadmium Sulfide"; 4, "Toxicity and Related Data on Selected Cadmium Compounds"; and 5, "Exposure Assessment." Greater detail on exposure data can be found in Appendix B "A Summary of Doses and Concentrations of ZnCdS Particles from Army's Dispersions Tests." This chapter combines information Dom the hazard-identification and dose-response assessments, as presented in Chapters 3 and 4, with the exposure-assessment, as presented in Chapter 5, to determine what magnitude of human exposure to ZnCdS might produce adverse health effects.
|
From page 69... ...
The health effects depend on the route by which the chemical enters the body, the changes in the chemical as it moves through the body, and the specific target organ that is the most susceptible. Noncancer risk assessment normally incorporates a number of "safety" or "uncertainty" factors, which are applied when there is a need to accommodate human response variability, including response in sensitive subgroups; to predict human response from animal data; to extrapolate from subchronic to chronic exposure; to predict a no-observed-adverse-effect level (NOAEL)
|
From page 70... ...
Therefore, the subcommittee chose to base its assessment of the potential toxicity of ZnCd S for noncancer health effects on the toxicity of CdS. Results of studies conducted by Oberdorster (1990)
|
From page 71... ...
studies, rats exposed to CdS at 39,600 mg-min/m3 had only a mild pulmonary response. Using those data and dividing by an uncertainty factor of 10 to extrapolate from a LOAEL to a NOAEL, by a factor of 10 to extrapolate from animal to human exposures, and by another factor of 10 to account for sensitive populations, one would not expect adverse health effects, even in sensitive populations, from exposure to cadmium sulfide in an insoluble form, such as ZnCdS, at 39.6 mg-m~n/m3 or 39,600 ,ug-m~n/m3.
|
From page 72... ...
As stated previously, this approach will therefore overestimate the risk. Assuming that 100% of the cadmium is bioavailable, estimates of lung-cancer risk were calculated for all test sites for which air concentrations are available based on the maximal recorded cumulative exposures of ZnCdS in the air and the carcinogenic potency derived from a study of workers exposed to cadmium by inhalation and oral ingestion of dust containing cadmium compounds.
|
From page 73... ...
The average daily exposure is directly proportional to the cumulative exposure on which the cancer risk estimate is based. The cancer risk estimates were calculated first on the basis of a lifetime of exposure and then reduced to the proportion of a lifetime during which people were actually exposed in the test areas.
|
From page 74... ...
Regardless, the relationship between excess cancer rates and exposures to cadmium compounds in these workers provides an estimate of lung-cancer potency of inhaled cadmium compounds. A simple linear regression provides a potency estimate of 14.6 x 10~ per ~ug-yr/m3.
|
From page 75... ...
states that "the carcinogenic risk associated with specific cadmium compounds could be overestimated or underestimated, because bioavailability has not been included in the risk assessment." However, the Occupational Safety and Health Administration came to the conclusion (OSHA 19924: "Record evidence and expert opinion [given by G Oberdorster and U
|
From page 76... ...
The human lung-cancer potency factor (probability of lung cancer per mg/kg cadmium per day average lifetime exposure) calculated earlier in this chapter is ~ I.7 per mg/kg of cadmium per day over a lifetime.
|
From page 77... ...
Estimated Maximal Estimated Maximal Exposure per Person, fig Lifetime RiskC 24,0x 10-6 1,2x 10-6 o,gx 10-6 0,4X 10-6 03 x 10-6 0 3 x 10 PaloAlto,CA(1962) 4.4 0.3 x 10-6 ChippewaNationalForest,MN 4.2 0.3 x 10-6 Oceanside, CA (on shore)
|
From page 78... ...
The lung-cancer potency was estimated from results in workers exposed to cadmium compounds at higher air concentrations for periods much longer than those of any people exposed in the ZnCdS releases. It is unknown whether the cancer potency (risk)
|
From page 79... ...
Hence, the contribution of this route of exposure, if any, to lung cancer was included in the potency estimate. CONCLUSIONS In the absence of adequate toxicity data on ZnCdS, the subcommittee considered it to be most appropriate to base its assessment of the potential toxicity of ZnCdS for noncancer health effects on the toxicity of CdS, an insoluble cadmium compound.
|
From page 80... ...
The potential exposures of people with the highest ZnCdS exposures from the Army tests in St. Louis were equivalent to the ambient airborne cadmium exposures of people living in typical urban areas for I-8 mot For the vast majority of people exposed to ZnCdS from the Army tests in St.
|
From page 81... ...
Hence, it is unlikely that anyone in the test areas developed lung cancer owing to direct exposure to cadmium from airborne releases of ZnCdS.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.