title: Air ions and respiratory function outcomes: a comprehensive review.
abstract: BACKGROUND
  From a mechanistic or physical perspective there is no basis to suspect that electric charges on clusters of air molecules (air ions) would have beneficial or deleterious effects on respiratory function. Yet, there is a large lay and scientific literature spanning 80 years that asserts exposure to air ions affects the respiratory system and has other biological effects.
  
  
  OBJECTIVE
  This review evaluates the scientific evidence in published human experimental studies regarding the effects of exposure to air ions on respiratory performance and symptoms.
  
  
  METHODS
  We identified 23 studies (published 1933-1993) that met our inclusion criteria. Relevant data pertaining to study population characteristics, study design, experimental methods, statistical techniques, and study results were assessed. Where relevant, random effects meta-analysis models were utilized to quantify similar exposure and outcome groupings.
  
  
  RESULTS
  The included studies examined the therapeutic benefits of exposure to negative air ions on respiratory outcomes, such as ventilatory function and asthmatic symptoms. Study specific sample sizes ranged between 7 and 23, and studies varied considerably by subject characteristics (e.g., infants with asthma, adults with emphysema), experimental method, outcomes measured (e.g., subjective symptoms, sensitivity, clinical pulmonary function), analytical design, and statistical reporting.
  
  
  CONCLUSIONS
  Despite numerous experimental and analytical differences across studies, the literature does not clearly support a beneficial role in exposure to negative air ions and respiratory function or asthmatic symptom alleviation. Further, collectively, the human experimental studies do not indicate a significant detrimental effect of exposure to positive air ions on respiratory measures. Exposure to negative or positive air ions does not appear to play an appreciable role in respiratory function.
authors.affiliation: Exponent, Health Sciences, 17000 Science Drive, Suite 200, Bowie, MD 20715, USA. wbailey@exponent.com.
authors.forename: Dominik D
authors.initials: DD
authors.lastname: Alexander
authors.forename: William H
authors.initials: WH
authors.lastname: Bailey
authors.forename: Vanessa
authors.initials: V
authors.lastname: Perez
authors.forename: Meghan E
authors.initials: ME
authors.lastname: Mitchell
authors.forename: Steave
authors.initials: S
authors.lastname: Su
mesh_terms: D000388:Air / Q000032:analysis*; D006801:Humans; D007477:Ions / Q000032:analysis; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D012119:Respiration
chemical_list: D007477:Ions
references.citation: Am J Phys Med. 1958 Feb;37(1):18-27
references.pmid: 13508856
references.citation: Ann Allergy. 1983 Oct;51(4):430-5
references.pmid: 6625226
references.citation: J Clin Invest. 1935 Jan;14(1):70-80
references.pmid: 16694283
references.citation: Thorax. 1984 Aug;39(8):594-6
references.pmid: 6474386
references.citation: Allergy. 1979 Jun;34(3):187-94
references.pmid: 495917
references.citation: Br Med J (Clin Res Ed). 1987 May 9;294(6581):1195-6
references.pmid: 3109576
references.citation: Thorax. 1976 Aug;31(4):428-32
references.pmid: 823659
references.citation: Dis Chest. 1966 Oct;50(4):343-52
references.pmid: 5924970
references.citation: Am J Phys Med. 1955 Dec;34(6):618-31
references.pmid: 13268624
references.citation: Thorax. 1983 Dec;38(12):919-22
references.pmid: 6364442
references.citation: Thorax. 1983 Aug;38(8):584-8
references.pmid: 6351332
references.citation: Int J Biometeorol. 1978 Dec;22(4):249-62
references.pmid: 750505
references.citation: J Allergy. 1960 Jul-Aug;31:370-4
references.pmid: 13847998
references.citation: Arch Environ Health. 1963 Dec;7:664-7
references.pmid: 14077212
references.citation: Ann Allergy. 1983 Sep;51(3):362-6
references.pmid: 6351676
references.citation: Thorax. 1993 Apr;48(4):330-3
references.pmid: 8511730
references.citation: Am J Phys Med. 1958 Apr;37(2):83-9
references.pmid: 13520928
references.citation: J Hum Ergol (Tokyo). 1993 Jun;22(1):1-9
references.pmid: 8064146
references.citation: Cochrane Database Syst Rev. 2003;(3):CD002986
references.pmid: 12917939
references.citation: Int J Radiat Biol. 1999 Dec;75(12):1523-31
references.pmid: 10622258
references.citation: Pediatrics. 1966 Sep;38(3):405-11
references.pmid: 5918389