title: Evaluation and application of the RD50 for determining acceptable exposure levels of airborne sensory irritants for the general public.
abstract: BACKGROUND
  The RD(50) (exposure concentration producing a 50% respiratory rate decrease) test evaluates airborne chemicals for sensory irritation and has become an American Society for Testing and Materials (ASTM) standard method. Past studies reported good correlations (R(2)) between RD(50)s and the occupational exposure limits, particularly threshold limit values (TLVs).
  
  
  OBJECTIVE
  The main purpose of this study was to examine the relationship between RD(50)s and human sensory irritation responses in a quantitative manner, particularly for chemicals that produce burning sensation of the eyes, nose, or throat, based on lowest observed adverse effect levels (LOAELs) reported for human subjects.
  
  
  METHODS
  We compared RD(50)s with LOAELs and acute reference exposure levels (RELs). RELs, developed by the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment, represent a level at which no adverse effects are anticipated after exposure. We collected RD(50)s from the published literature and evaluated them for consistency with ASTM procedures. We identified LOAELs for human irritation and found 25 chemicals with a corresponding RD(50) in mice.
  
  
  CONCLUSIONS
  We found the relationship between RD(50)s and LOAELs as log RD(50) = 1.16 (log LOAEL) + 0.77 with an R(2) value of 0.80. This strong correlation supports the use of the RD(50) in establishing exposure limits for the public. We further identified 16 chemical irritants with both RD(50)s and corresponding acute RELs, and calculated the relationship as log RD(50) = 0.71 (log REL) + 2.55 with an R(2) value of 0.71. This relationship could be used to identify health protective values for the public to prevent respiratory or sensory irritation.
  
  
  CONCLUSIONS
  Consequently, we believe that the RD(50) has benefits for use in setting protective levels for the health of both workers and the general population.
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California 94612, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kuwabara
authors.forename: George V
authors.initials: GV
authors.lastname: Alexeeff
authors.forename: Rachel
authors.initials: R
authors.lastname: Broadwin
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Salmon
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects* / Q000737:chemistry / Q000145:classification; D000818:Animals; D002140:California; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure / Q000592:standards*; D004784:Environmental Monitoring / Q000379:methods / Q000592:standards; D015386:Hazardous Substances / Q000009:adverse effects* / Q000145:classification; D006801:Humans; D007509:Irritants / Q000009:adverse effects* / Q000737:chemistry / Q000145:classification; D008297:Male; D008452:Maximum Allowable Concentration; D051379:Mice; D011634:Public Health / Q000592:standards*; D012119:Respiration / Q000187:drug effects; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012678:Sensation Disorders / Q000139:chemically induced* / Q000209:etiology; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D000393:Air Pollutants; D015386:Hazardous Substances; D007509:Irritants