title: Evaluation of the experimental basis for assessment factors to protect individuals with asthma from health effects during short-term exposure to airborne chemicals.
abstract: BACKGROUND
  Asthmatic individuals constitute a large sub-population that is often considered particularly susceptible to the deleterious effects of inhalation of airborne chemicals. However, for most such chemicals information on asthmatics is lacking and inter-individual assessment factors (AFs) of 3-25 have been proposed for use in the derivation of health-based guideline values.
  
  
  OBJECTIVE
  To evaluate available information in attempt to determine whether a general difference in airway response during short-term exposure between healthy and asthmatic individuals can be identified, and whether current AFs for inter-individual variability provide sufficient protection for asthmatics.
  
  
  METHODS
  After performing systematic review of relevant documents and the scientific literature estimated differential response factors (EDRF) were derived as the ratio between the lowest observed adverse effect levels for healthy and asthmatic subjects based on studies in which both groups were tested under the same conditions. Thereafter, the concentration-response relationships for healthy and asthmatic subjects exposed separately to four extensively tested chemicals (nitrogen dioxide, ozone, sulfuric acid, sulfur dioxide) were compared on the basis of combined data. Finally, a Benchmark Concentration (BMC) analysis was performed for sulfur dioxide.
  
  
  RESULTS
  We found evidence of higher sensitivity among asthmatics (EDRF > 1) to 8 of 19 tested chemicals, and to 3 of 11 mixtures. Thereafter, we confirmed the higher sensitivity of asthmatics to sulfuric acid and sulfur dioxide. No difference was observed in the case of ozone and nitrogen dioxide. Finally, our BMC analysis of sulfur dioxide indicated a ninefold higher sensitivity among asthmatics.
  
  
  CONCLUSIONS
  Although experimental data are often inconclusive, our analyses suggest that an AF of 10 is adequate to protect asthmatics from the deleterious respiratory effects of airborne chemicals.
authors.affiliation: a Unit of Work Environment Toxicology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden and.
authors.forename: Mia K V
authors.initials: MK
authors.lastname: Johansson
authors.affiliation: a Unit of Work Environment Toxicology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden and.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Johanson
authors.affiliation: a Unit of Work Environment Toxicology , Karolinska Institutet, Institute of Environmental Medicine , Stockholm , Sweden and.|b Swedish Toxicology Sciences Research Center , Södertälje , Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Öberg
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D001249:Asthma / Q000139:chemically induced / Q000175:diagnosis* / Q000517:prevention & control; D016208:Databases, Factual; D006801:Humans; D009585:Nitrogen Dioxide / Q000633:toxicity; D010126:Ozone / Q000633:toxicity; D013458:Sulfur Dioxide / Q000633:toxicity; D013464:Sulfuric Acids / Q000633:toxicity
chemical_list: D000393:Air Pollutants; D013464:Sulfuric Acids; D013458:Sulfur Dioxide; D010126:Ozone; C033158:sulfuric acid; D009585:Nitrogen Dioxide
keywords: Guideline values; inhalation; nitrogen dioxide; ozone; risk assessment; sulfur dioxide; sulfuric acid; susceptible populations