Table 2 Air ion exposure assessment, psychological measures, and study findings

Silverman and Kornblueh 1957[27]^a,b

Negative air ion (30 minutes)

Not reported

Human electroencephalogram

Decrease in alpha frequency in most subjects; half of the subjects reported relaxation and sleepiness with ionization (slightly more frequent for (−) than (+) ion exposure); one consistent finding was a decrease in alpha frequency during negative or positive ionization (or both) in all but two subjects. Findings reported as “transient.”

Positive air ion (30 minutes)

Activations by hyperventilation, apnea, photic stimulation and sleep (natural)

McGurk, 1959[17]^c

Negative air ion (5 hours)

8.0 × 10³ ions/cm³

Self-reported feelings of comfort, ease by which subjects worked on a cognitive task, and reactions to the test room atmosphere

Regarding negative ionization, a significant percent of subjects appeared to detect ionization condition despite blinding and reported more pleasant feelings.

Positive air ion (2 hours)

Regarding positive ionization, subjects reported more unpleasant feelings.

Yaglou, 1961[19]^b

Negative air ion (1–2 hours)

5,000 to 10,000 ions/cm³ air

Self-reported impressions (indifference, relaxation, air freshness, headache, respiratory irritation, restlessness)

Subjectively, positive air ions seemed to increase the incidence of upper respiratory irritation in the winter, while negative air ions had little or no effect on the quality of air.

Positive air ion (1–2 hours)

5% of subjects reported feeling relaxed when exposed to positive air ions; 17% reported feeling relaxed when exposed to negative air ions; and 21% of subjects reported feeling relaxed under control conditions

Yaglou, 1961[19]^b

Negative air ion (1–2 hours)

10⁵-10⁶ ions/cm³ air

Self-reported impressions (indifference, relaxation, air freshness, headache, respiratory irritation, restlessness)

Subjectively, negative air ions did not alleviate joint symptoms, while positive air ions seemed to make the symptoms worse; a higher frequency of patients reported feeling relaxed or sleepy, or both when exposed to negative versus positive air ions

Positive air ion (1–2 hours)

Assael et al., 1974[11]^b

Negative air ion (45 minutes)

3.5 × 10⁵ ions/cm³

EEG parameters:

Decrease in alpha frequency manifestation of general relaxation induced by negative air ions. Increase of amplitude interpreted as improvement of perception and apperception. Subjectively, all patients experienced initial relaxation followed by alertness connected with moving of alpha-waves from occipital to frontal areas.

frequency (Hz)

amplitude (μV)

spreading of alpha waves area

synchronization of right and left hemispheres

Self-reported relaxation, alertness, working capacity, relief

Albrechtsen et al., 1978[37]^b,c

Negative air ion (Experiment I: 8 hours; Experiment II: 15 minutes) Positive air ion (Experiment I: 8 hours; Experiment II: 15 minutes)

300-9,000 ions/cm³

Mental performance:

No significant effects of positive or negative air ions found.

number of tasks per hour

Subjective voting based on % scale:

extent of exertion

perception on air quality

perception of tasks

current feeling (sleepy vs. alert)

Charry and Hawkinshire, 1981[15]^a

Positive air ion (1.5 hours )

Positive air ions: 2.0-3.0 × 10⁴ ions/cm³

Mood Adjective Check List

For most subjects, mood changes induced by air ion exposure characterized by increased tension and irritability.

Ambient condition (contained both) (1.5 hours)

Ambient: 3.0 × 10² ions/cm³

Sharav Questionnaire (mood)

Hawkins, 1981[38]^{b, c}

Negative air ion (Weeks 5 to 12- on continuously)

Negative air ion: 2.0-3.5 × 10³ ions/cm³

Personal ratings of thermal comfort, stuffiness, alertness, well-being

Negative air ion exposure associated with higher subjective ratings of alertness, atmospheric freshness, environmental/personal warmth, and a reduction in the overall complaint rate by 50%. Night-shift working was associated with discomfort and ill-health. Positive air ion effects were not explicitly discussed.

Positive air ion (Weeks 5 to 12- on continuously)

Positive air ion: 50–125 ions/cm³ air

Tom et al., 1981[34]^a,b

Negative air ion (15 minutes)

Negative air ion: 16,160 ions/cm³

Likert scale survey for psychological state (difficulty of concentration, energetic, mood state, sociable, relaxed)

Subjects reported being more energetic and finding it easier to concentrate under the experimental condition than the control condition. Negative air ion exposure had a positive effect on certain aspects of human performance and mood.

Control (natural environment): 204.4 ions/cm³

Buckalew and Rizzuto, 1982[12]^a,b

Negative air ion (6 hours)

Not reported

Taylor Manifest Anxiety Scale (TMAS)

Mood index data showed significant changes in the subjective perception of both physiological state (relaxation increased) and psychological state (irritability, depression, and tenseness decreased while calmness and stimulation increased).

Self-report Mood Index

Dantzler et al., 1983[25]^a

Negative air ion (6 hours)

Negative and positive air ions: 60,000-110,000 ions/cm³

Sharav Questionnaires 1 and 2 Mood Adjective Check List

Patients’ mood did not differ significantly between the two ion exposures.

Positive air ion (6 hours)

Baron et al., 1985[28]^a

Negative air ion (20 minutes)

Ambient condition: 2.0-3.0 × 10² ions/cm³

Self-reported affect (Profile of Mood States survey)

Exposure to moderate or high levels of negative air ions significantly enhanced aggression by Type A subjects, but not among others. Negative air ions produced positive shifts in reported moods in the absence of provocation, but negative shifts in moods in the presence of provocation.

Moderate condition: 4 × 10⁴ ions/cm³

Aggression measured by mean level of heat selected by subjects on each of the 20 occasions when the red light appeared

High condition: 7.0-8.0 × 10⁴ ions/cm³

Memory measured by the number of traits and the number of behaviors subjects could recall about the accomplice

Deleanu and Stamatiu, 1985[29]^a,b,d

Negative aeroionotherapy (daily treatment of 15–50 minutes for 10–30 days)

1-1.5 × 10⁴ ions/cm³

Amelioration of asthenia, depressive reactions, anxiety, excitability and irascibility, cephalea, insomnia, and general disposition in patients with various psychiatric disorders

In most treated patients, a diminution or even the disappearance of the target symptoms was obtained (asthenia, depressive reactions, anxiety, irascibility, cephalea, insomnia, and general disposition).

Gianinni et al., 1986[16]^a

Negative air ion (20 minutes)

Negative air ion: not reported

Brief Psychiatric Rating Scale

Cations were found to increase anxiety, excitement, and suspicion. Anions reversed the effects of cations and, in addition, reduced suspicion and excitement to levels below those occurring before cationization.

Positive air ion (20 minutes)

Positive air ion: 2.9 × 10³ ions/cm³

Gianinni et al., 1986/87[30]^a

Positive air ion (2 hours)

2,050-2,300 ions/cm³

Brief Psychiatric Rating Scale

Symptoms of anxiety and excitement significantly increased. During the time of exposure, serum serotonin levels also increased significantly.

Finnegan et al., 1987[40]^c

Negative air ion (6–8 weeks)

1.84 × 10³ ions/cm³

Personal comfort rating

No significant effect on personal comfort found. Effects on symptoms were non-significant except for URTI and nausea in the high negative air ion period.

Hedge and Collis, 1987[18]^a

Negative air ion (7 hours)

2 × 10⁴ ions/cm³

Mood Adjective Check List

Evidence for beneficial effects of negative air ions on mood and performance could not be demonstrated.

Two cognitive tasks:

naming 24 different colors printed on card

Stroop Colour Word test

Lips et al., 1987[13]^b,c

Negative air ion Weeks 2 and 4 - on continuously; Week 3 - mornings only

5 × 10⁴ ions/cm³

10 linear scales (rated 0 to 10) on which each subject was asked to assess his or her well-being and the quality of the environment

After their exposure to enhanced negative air-ion concentrations, the subjects' assessments of both their own well-being and the quality of the environment improved significantly: neither harmful effects of exposure to enhanced levels of negative air ions nor changes in perceived thermal comfort were detected.

Misiaszek et al., 1987[14]^a,b

Negative air ion Phase I: 1 hour; Phase II: 1.5 hours

Phase I: 40,000-60,000 small, 50–1000 medium, 50–4,000 large ions/cm³

State Trait Anxiety Inventory and Inpatient Multidimensional Psychiatric Scale

Phase I: All subjects fell to sleep, reported being calm afterwards; manic behavior reappeared 5–10 minutes after treatment

Phase II: 3/4 subjects fell to sleep, 1 subject appeared less agitated; manic behavior reappeared 5–10 minutes after treatment

Phase II: 50,000-70,000 small, 50–3,200 medium, 50–7,000 large ions/cm³

Reilly and Stevenson, 1993[33]^a

Negative air ion (30 minutes pre-test + 40 minutes during test)

1.72 × 10⁵ ions/cm³

Measurements were made of state anxiety according to Spielberger et al. (1970)

There was no significant effect of air ions on state anxiety pre-or post-exercise or on the perception of effort.

Terman and Terman, 1995[6]^d

Negative air ion (30 minute sessions for 20 days)

Low density: 1.0 × 10⁴ ions/cm³

SIGH – SAD

The severity of depressive symptoms decreased selectively for the group receiving high-density treatment. When a remission criterion of 50% or greater reduction in symptom frequency/severity was used, 58% of subjects responded to high-density treatment while 15% responded to low-density treatment.

Clinical Global Impressions Scale

High density: 2.7 × 10⁶ ions/cm³

Watanabe et al., 1997[35]^a,c

Negative air ion (10 minutes)

2.0 × 10⁴ ions/cm³

Self-reported feelings of temperature, pleasantness, fatigue, and sweating

There were no differences in the moods of these persons or changes in their blood pressures between the two saunas.

Terman et al., 1998[8]^b,d

Negative air ion (30 minutes per day for 10–14 days)

Low density: 1.0 × 10⁴ ions/cm³High density: 2.7 × 10⁶ ions/cm³

SIGH – SADSelf-rating version of the SIGH-SADSleep patterns

Improved depression rating of 42-50% and 20-40% remission rate. Described as a "small effect" in period 1 and "large effect" in period 2. Analysis of depression scale percentage change scores showed low-density air ion response to be inferior to all other groups, with no other group differences. Sleep measures subjects given morning light awakened 0.62 ± 0.62 hours earlier than at baseline; negative air ions, 0.41 ± 0.37 hours earlier; and evening light, 0.09 ± 0.58 hours earlier.

Nakane et al., 2002[10]^a

Negative air ion (40 minutes during task or 30 minutes post-task)

5.5-7.3 × 10³ ions/cm³

Japanese version of the State-Trait Anxiety Inventory, Anxiety StateSalivary cortisol and chromogranin A-like immunoreactivityTask performance

The increase in the CgA-like IR level was attenuated by the exposure to negative air ions during the task. The exposure to air ions during the recovery period following the task was effective for rapidly decreasing the CgA-like IR level that had increased after the task. These effects by negative air ions were also observed using STAI-S. Task performance was slightly but significantly improved by the presence of negative air ions.

Iwama et al., 2004a[39]^b

Negative ion (not reported)

3000 parts/cm^3f

Degree of tension: 1 = relaxed; 2 = normal tension; 3 = mild tension; 4 = moderate tension; and 5 = severe tension

Degree of tension decreased significantly and more rapidly in the negative ion-rich environment.

Goel et al., 2005[22]^b,d

Negative ion (1 hour upon wakening for 5 weeks)

Low density: 1.7 × 10¹¹ ions/s [1 × 10⁴ ions/cm³]^e

SIGH – SAD

SIGH-SAD score improvement was 51.1% for high-density ions v. 17.0% for low-density ions. Remission rates were 50% and 0%, respectively.

High density: 4.5 × 10¹⁴ ions/s [2.7 × 10⁷ ions/cm³]^e

Evening saliva samples obtained before and after treatment for ascertainment of circadian melatonin rhythm phase

Goel and Etwaroo, 2006[5]^a,b,d

Negative ion (30 minutes for three consecutive evenings)

Low density: 1.7 × 10¹¹ ions/s [1 × 10⁴ ions/cm³]^eHigh density: 4.5 × 10¹⁴ ions/s [2.7 × 10⁷ ions/cm³]^e

BDI

The three active stimuli (bright light, auditory stimuli, or high-density negative ion exposure), but not the low-density placebo, reduced depression, total mood disturbance and/or anger within 15–30 min.

The Profile of Mood

States Questionnaire

The Karolinska Sleepiness Scale

Likert scales assessed four aspects of stimulus perception using a 7-point scale. Subjects rated stimulus hedonics and intensity, as well as its effects on mood and on alertness

Terman and Terman, 2006[7]^b,d

Negative ion (93 minutes before waking up)

Low density: 1.7 × 10¹¹ ions/s [1 x 10⁴ ions/cm³]^e

SIGH – SAD

Post-treatment improvement results were high-density ions, 47.9%; and low-density ions, 22.7% (significantly different).

High density: 4.5 × 10¹⁴ ions/s [2.7 x 10⁷ ions/cm³]^e

Emergence or exacerbation of depression, sleep, appetite/weight, headache

Gianinni et al., 2007[26]^a

Negative ion (1 hour)

3 × 10³ ions/cm³

Brief Psychiatric Rating Scale

A significant anti-manic effect was observed: total rating scores declined with anion treatment.

Malcolm et al., 2009[32]^a,b

Negative ion (30 minutes pre-test and 60 minutes during test)

Not reported

Subjective state measured by six visual analogue scales for happiness, sadness, hostility, alertness, anxiety and calmness.

Association between BDI score and treatment; increased recall and recognition of positive terms versus negative terms; findings indicate that HDNI treatment produces a positive bias in emotional recall and recognition.

The emotional test battery consisted of an emotional categorization task with surprise emotional recall and recognition, a facial expression recognition test, and a dot-probe task of attention with masked and unmasked conditions.

Flory et al., 2010[4]^d

Negative ion (30 minutes for 12 days)

Low density: 4.0 × 10³ ions/cm³

SIGH – SAD–Self Rating:

Subjects in all four groups showed significant score decreases on the SIGH-SAD-SR and on the BDI. For raw scale scores, neither main effects of treatment nor interactions between treatment and time were significant. When remission outcome criteria were used, exposure to high-density negative ions was more effective than either of the two placebo conditions, although the difference was not significant.

High density: ≥ 2.0 × 10⁶ ions/cm³

BDI

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for SAD

Malik et al., 2010[9]^a

Negative ion (2 hours)

>1,000,000 counts/cm³

Self-reported computer-oriented stress, physiological and psychological stress

A significant decline in computer-oriented stress and psychological stress was noticed post-computer operations in presence of negative ions.

Dauphinais et al., 2012[24]^d

Negative ion (7.5 min/day or 15 min/day if tolerable for 8 weeks)

1.7 × 10¹¹ ions/s [1 × 10⁴ ions/cm³]^e

SIGH-SAD

No significant difference in SIGH-SAD scores between light therapy and low-density negative ion groups at study end or in the proportions of responders or remitters in these groups.

Harmer et al., 2012[31]^a,b,d

Negative ion (30 minutes pre-test and 60 minutes during test)

Not reported

Subjective state measured by six visual analogue scales (happiness, surprise, sadness, fear, anger, and disgust), BDI, and State-Trait Inventory

No effect on anxiety, depression (BDI), alertness, and recall of emotional words. HDNI treatment decreased recognition of faces showing disgust and increased recognition of happy faces, and increased recognition of and vigilance to positive words. HDNI increased recognition memory of positive words only in the SAD group. The findings indicate that HDNI treatment produces a positive bias in emotional recall and recognition.

The emotional test battery consisted of an emotional categorization task with surprise emotional recall and recognition, a facial expression recognition test, and a dot-probe task of attention with masked and unmasked conditions.