Table 2.

Experimental design and respiratory outcomes

Study author and year	Ion polarity	Ion concentration	Results
Infants
[8]	Negative or positive	Calibrated to deliver 1 × 104 ions on 1 cm2 area 10 cm away; negative or positive ions.	Negative ion exposure - severity of bronchospasm decreased from 3 to 0.3 after negative ion exposure. Average of 7.5 hrs between start of exposure and effects. Respiratory rate decreased on average 27% after first exposure period. Severity of bronchospasm returned in 7/16 subjects who were followed with cessation of ion exposure; increase in respiratory rate returned in 6/10 subjects who were followed. Positive ion exposure - severity of bronchospasm increased from about 0 to average of 2 after positive ion exposure. Respiratory rate (measured in only 2 subjects) increased on average 20-25% after 3 hrs. Response to positive ion exposure "disappeared spontaneously" after 10 to 50 hrs despite continued exposure. Positive and negative ion exposures - effects are lost when ion concentrations were reduced by a factor of 10 to 20. Control group (at different hospital) - bronchospasm decreased from N.S. to 0 or increased from 0 to 1 after 6 to 7 days of conventional asthma treatment.
Child-Adolescent (up to 20)
[6]	Negative	5 × 105 - 10 × 105 ion/cm3; negative; 4 × 105 - 5 × 105 ion/cm3; negative	Pre-exercise mean FEV1 before ion exposure 1.36 L/min (SEM 0.07) and after ion exposure 1.35 L/min (SEM 0.08) not significantly different. After exercise challenge mean delta FEV1: Controls 29% of baseline (SE 5%), Exposed 21% (SE 3%) was significantly different (t-test, p<0.015). Histamine challenged mean delta FEV1 before ion exposure was 70% (SE 6%) and after ion exposure was 69% (SE 5%) not significantly different; median provocative dose of histamine was higher with ion exposure than control but difference was not significant, and some patients became more and some less sensitive to histamine challenge after ion exposure.
[15]	Negative	Concentration N.S.; negative	No significant difference in lung function when comparing exposed vs unexposed groups (unpaired t-test) or prior to exposure vs post-exposure for the exposed group (paired t-test).
[16]	Positive	5 × 105 - 10 × 105 ion/cm3; positive	Mean delta FEV1 = 35.3% (SEM 5%) with positive ion exposure; 24.7% (SEM 5.3%) control; the difference was significant (paired t-test, p<0.04); other parameters showed no significant change.
[14]	Not specified	N.S.	Difference between active ionizer vs placebo ionizer was significant for airborne allergen concentration (reduction during active ionizer; p<0.0001 Mann–Whitney U-test; p<0.01 Chi-Square test), but non-significant for PEFR, symptom scores, and medication scores. Authors noted increased nighttime cough but difference did not reach a standard significance (p=0.055).
Overlapping child-adult
[7]	Negative	Concentration N.S.; negative	Individual results - Four patient's mean morning PEFR during treatment period significantly improved when comparing to control period (Mann–Whitney U-test; p<0.05). Three patient's mean evening PEFR during treatment period significantly improved when comparing to control period (p<0.01). Three patient's mean morning and evening PEFR significantly decreased when in transition from exposure to control period (p<0.001). Two patients reported subjective improvement during exposure period. Group results - Lung function measurements (from self- and investigator-administered) & diary card scored by investigator showed no significant difference during exposure and control periods (two-way analysis; p>0.4). Lung function measurements (from self- and investigator-administered) alone scored by independent physicians showed no significant difference during exposure and control periods (p>0.7).
[17]	Negative	Concentration N.S.; negative	Hay fever patients (n=17) = 35.3% relief, 47.06% complete relief, 17.64% no relief. All patients (n=27) = 29.63% relief, 33.33% complete relief, 37.04 no relief.
[18]	Negative or positive	Negative 1,200 to 2,600 ion/cm3; Positive 2,000-6,500 ion/cm3.	Negative ion exposure (n=54) = 62.9% relief; positive ion exposure (n= 5) = 0% relief; control (n = 15) = 6.6% relief. Asymptomatic of hay fever prior to exposure but developed symptoms during exposure: negative ion = 0/37; positive ion = 6/10; control = 1/2.
[10]	Negative or positive	1-50% of generated 5,000-1,500,000 ion/cm3; positive or negative	Effects of ion exposure similar regardless of polarity or ion concentration. Tabular summary of averages of measured parameters with ion exposure during basal, 2–4 hrs after breakfast, and 3–5 hrs after lunch. Positive ion exposure resulted in a group of individuals reporting subjective sensation of dryness and irritation of the nose and throat, and frontal headache. Negative ion exposure led to relaxation, and decrease in physiological parameters. Freshness of air felt during negative ion exposure but preference was not strong enough to be significant.
[19]	Negative or positive	N.S. (rate of 1 × 10-10 amp); negative and positive	35/40 experiments saw no effects, and 5/40 experiments with negative or positive ion exposure saw mild to moderate wheezing and dyspnea.
[20]	Negative or positive	~30,000 ion/cm3; negative or positive.	Group 1 - significant differences in FEV1 over the 4 ion and no ion exposures (Friedman's test, p<0.04). Individual FEV1 higher during both negative (20/27 values) and positive (21/27 values) ion exposure intervals. No significant difference (Friedman's test) in subjective scoring of temperature (p=0.2), air quality (p=0.3), and breathing comfort (p=0.7). Group 2 - no significant difference in histamine threshold after exposure to either ion exposures (Friedman's test, p<0.4) and no change was "demonstrated" (Wilcoxon match pair) in FEV1 from no ion to either positive or negative ion exposure.
Adult
[21]	Negative or positive	300 – 9,000 ions/cm3	No significant effects of ionization were observed in either experiment except in certain partial means for the mental performances in Experiment II.
[22]	Negative or positive	60,000 - 110,000 ion/cm3; negative or positive	Mean FEV1 and pulse not significantly different between positive and negative ion exposure or from baseline (paired two-tail t-test); blood pressure significantly higher with negative ion exposure (p <0.01; paired two-tail t-test) and after 2 hours of positive ion exposure (p <0.05; paired two-tail t-test); no significant difference between positive and negative ion exposure in serum theophylline, urinary 5HIAA, or in questionnaire results.
[23]	Negative	1841 ion/cm3; negative	No significant effects observed, except for slightly more complaints of upper respiratory tract infection and nausea that may have been attributable to mild flu-like disorder in this study population.
[3]	Negative or positive	5 × 106 - 6 × 106 ion/cm3; positive or negative	Results for group-level data: basal or total metabolism/oxygen consumption, systolic and diastolic blood pressure = no significant difference between positive, negative, and control exposures. Self-reported subjective state - if 13 comment types are grouped as undesirable or desirable state, "slight difference" (higher) in frequency of reported undesirable state during positive ion than negative ion or control exposures (no statistical comparison shown).
[24]	Negative	172,000 ion/cm3; negative ions	With negative ion exposure and at rest, core (rectal) temperature, heart rate, VO2, and VE averaged over four times during the day is reduced significantly in comparison to neutral (no ion exposure) condition (three-way ANOVA, p<0.05). At both 90W and 180W exercise trials, rectal temperatures during the day with negative ion exposure averaged over four times were significantly different from no ion exposure (three-way ANOVA, p<0.05); differences between exposure and no exposure in heart rate (absolute or difference from rest) were insignificant; differences in absolute VO2 and VE between exposure and no exposure were insignificant; differences in the change from rest in VO2 and VE were significant (three-way ANOVA, p<0.05). Differences between exposure and no exposure in the modeled circadian rhythm acrophase amplitude of rectal temperature was significantly during rest (t-test, p<0.05) but not during both exercises. Differences between exposure and no exposure in the modeled circadian rhythm for VO2 and VE were not significant. Differences between exposure and no exposure in perceived exertion during exercise were not significant.
[25]	Negative or positive	Positive and negative ions were measured. Positive ion peak concentration defined as >=2,000 ion/.	Difference between mean peak flow prior to weather fronts and during peak positive ion concentration versus same times during normal days were non-significant (paired t-test).
Unspecified adult populations
[2]	Negative or positive	100,000 ion/cm3; negative, positive, or placebo	No significant pulmonary function differences comparing treatments and clinical conditions. Data on grading presented in Figure 1. Results comparing patient grouped by clinical conditions as percentages for each pulmonary function presented.
[27]	Negative or positive	125,000 or greater ion/cm3; positive and negative	Mean and S.D. of % change in FVC, FEV1, and MMFR with positive, negative, or control exposure tabulated for each comparison. No significant changes or differences with positive, negative, or no ionization.
[28]	Negative or positive	500,000 ion/cm3	1 hour exposure: no significant change with negative ion exposure, 9 subjects; 3 hour exposure: ventilation Factor = 52.2% (S.D. 4.3%) with negative ion exposure; subjectively, 10/33 felt better, 1 worse, and 22 no effect. No correlation between subjective improvement and pulmonary function measurements, 22 subjects; 2 week exposure: ventilation Factor =41.8% (S.D. 5%) with negative ion exposure; subjectively, 10/33 felt better, 1 worse, and 22 no effect. No correlation between subjective improvement and pulmonary function measurements, 15 subjects.
[13]	Negative	±150,000 ion/cm3; measured monthly. Group 1 mean = 203,000 ion/cm3; Group 2 mean = 183,000 ion/cm3.	No significant differences in PEFR, symptom scores, and medication scores were found between active ionizer vs placebo or no ionizer use (paired t-test).
[9]	Negative or positive	Body as ion collector experiment: 32,000 positive ion/cm3 or 80% of 32,000 (approx 26,000) negative ions/cm3; biological effects study 32,000 ion/ positive or negative.	Biological effects study: Study I-16 with positive ion exposure had symptoms; Study II- 4/13 with negative ion exposures had symptoms; Study III- 2/7 during negative ion exposure and 7/7 during positive ion exposure; Study IV- 3/20 with symptoms during second no ion period, 17/20 with symptoms during positive ion exposure, and 6/20 with persistent symptoms during last no ion exposure period; Study V-1/21 with symptoms during no ion exposure and 5/21 during placebo ion exposure; Maximum breathing capacity study-reduced from 35 L/min to 25 L/min after positive ion exposure, no reduction after negative ion exposure; Effects of grounding study-5/11 developed symptoms with positive ion exposure and grounding, 9/11 developed symptoms with positive ion exposure and no grounding; Temperature and humidity study-no difference in symptoms, during low humidity the symptoms were more frequent and more severe than comparison.

N.A. - not applicable; N.S. - not specified. Forced expiratory volume - FEV; forced vital capacity-FVC; peak expiratory flow rate-PEFR; standard error of mean-SEM; standard deviation-S.D.; 5-hydroxyindole acetic acid-5HIAA; oxygen consumption-VO₂; minute volume-VE.