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Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 8
End Point/Concentration/Rationale: no effect level for lethality
Total uncertainty factor: 10
Interspecies: 3 - propylenimine is a reactive direct-acting alkylating agent, and the AEGL-3 effects are expected to be confined to the respiratory tract. Respiratory tract damage appears to be due to the direct effect of an alkylating agent on the respiratory epithelium; this mechanism is expected to be similar among species. The time of onset of signs and symptoms of exposure on the eyes and respiratory tract is expected to be delayed in both humans and animals.
Intraspecies: 3 - the effects appear to involve direct contact of the eyes or respiratory epithelium with a very reactive alkylating agent. Studies have shown that DNA damage is probably the initiating step in a cascade of events leading to cell damage after exposure to alkylating agents, and DNA damage is persistent in respiratory and systemic organs following inhalation exposure to these agents.
Modifying Factor: 1
Animal to Human Dosimetric Adjustment: None applied.
Time Scaling: Cn × k = t, where n = 0.91 derived empirically from LC50 data in which guinea pigs were exposed to ethylenimine for times ranging from 5 min to 480 min.
Data Adequacy: Very few data were available for deriving AEGL-3 values for propylenimine. A standard acute lethality study has not been conducted for propylenimine; therefore, the time-response study in which rats and guinea pigs were exposed to 500 ppm for different time periods was used to derive AEGL-3 values. The data for the guinea pig showed that this species is more sensitive to propylenimine exposure than the rats; lethality occurred after exposure of guinea pigs to 500 ppm for 60 min and after exposure of rats to 500 ppm for 240 min.