User Guide to Thresholds and Classification - Environmental ...

148User Guide for Thresholds and Classificationsiv.Acute inhalation toxicityA hazard classification may be assigned for acute inhalation toxicity for aerosol products. Theclassification assigned should also take into account the propellant in the aerosol.10.3.3. Classification of mixtures based on ingredients of the mixture (additivity formula)Data available for all ingredientsThe ATE of ingredients should be considered in the following way.Include ingredients (including impurities and additives) with a known acute toxicity, that fall into any ofthe HSNO Act acute toxicity categories.Ignore ingredients that are presumed not acutely toxic (for example, water and sugar).Ignore ingredients if the oral limit test does not show acute toxicity at 2,000 mg/kg bw.Ingredients that fall within the scope of this paragraph are considered to be ingredients with a known ATE.The ATE of the mixture is determined using the ATE values for all relevant ingredients, according to thefollowing formula for oral, dermal, or inhalation toxicity:C a /ATE a + C b /ATE b + ...+ C z /ATE z = 100/ATE mixWhere:C a = percentage of the component in the substance as a mixtureATE a = acute toxicity estimate of componentATE mix = estimated LD 50 of the mixtureSee the worked examples in Appendix 10B.Data are not available for one or more ingredients of the mixtureWhen an ATE is not available for an individual ingredient of the mixture, but information such as that listedbelow can provide a derived conversion value (see Table 10.2) the formula above may be applied.This may include evaluating:the extrapolation between oral, dermal, and inhalation ATEs, 2 which could require appropriatepharmacodynamic and pharmacokinetic data;evidence from human exposure that indicates toxic effects but does not provide lethal dose data;evidence from any other toxicity tests and assays available on the substance that indicates toxic acuteeffects but does not necessarily provide lethal dose data; ordata from closely analogous substances using structure activity relationships.This approach generally requires substantial supplemental technical information and a highly trained andexperienced expert to reliably estimate acute toxicity. If such information is not available, follow theprovisions below.2For ingredients with ATEs available for other than the most appropriate exposure route, values may be extrapolatedfrom the available exposure route to the most relevant route.January 2012 EPA0109