Table 3.

Reported overall study conclusions for air ions and pulmonary and ventilatory measures

Study	Ion polarity evaluation			Conclusions reported in article
	Negative	Positive	Both
[27]			X	“It is concluded that we have not shown any effect of highly ionized air upon these ventilator tests.”
[6]	X			“It is concluded that negative ionization of inspired air can modulate the bronchial response to exercise but the effect on the response to histamine is much more variable.” [Note: no effect seen in non-exercise challenge]
[16]		X		“It is concluded that positive ionization aggravates the bronchial response to exercise.” [Note: only significant difference was for post-exercise FEV comparisons]
[22]			X	“…exposure to positive or negative small air ions did not influence the clinical condition…findings do not support a significant role of small air ions in exacerbation or treatment of bronchial asthma.”
[21]			X	“A slight but significant (at the 5% level) improvement in the lung function was demonstrated during positive as well as negative ion exposure…”
[20]			X	“A slight but significant (at 5% level) improvement in the lung function was demonstrated in nine patients during positive as well as negative ion exposure…”
[28]			X	“No significant changes were observed in the lung volume measurements…after breathing the negative ions.” [Note: no effect for short or long exposure] “To date our work has failed to demonstrate any significant objective changes which can be measured from breathing of negative or positive ions either favorable or unfavorable.”
[13]	X			“There were no significant differences in PEFR…between the periods that active ionizers and either no ionizers or placebo ionizers were in operation…study has failed to show a statistically significant benefit in asthmatic subjects from the use of negative ion generators.”
[7]	X			“…it is unlikely that exposure to negative ions will be of significant benefit in the majority of patients with asthma…the effects of negatively ionized air on such patients remains to be determined.”
[2]			X	“…failed to show any significant effects when judged by subjective clinical appraisal or evaluated by objective pulmonary function…ionization should not be recommended as a therapeutic adjuvant in the treatment of these diseases.”
[25]		X		“The mean peak flow rates in this group of patients did not vary significantly with the changes in ion levels or other meteorologic factors which resulted from the passage of these weather fronts.”
[14]	X*			“This study indicates that the use of ionizers cannot be recommended in the homes of asthmatic subjects to improve their symptoms.”
[10]			X	“No significant changes were found in…exposures of between one and two hours to either positive or negative ions, compared to changes which occurred in control experiments.” “As in our previous work, nothing definite was found to justify the use of artificial ionization in ventilation or air conditioning.” [Note: upper respiratory irritation increased after exposure to positive ions, based on subjective responses but may be due to weather effects.]
[9]			X	“…positive ions produce irritation of the respiratory tract especially when the humidity is low, the patient is grounded and high ion densities are employed.” [Note: primarily based on subjective symptom responses, not objective clinical measurements.]
[10]			X	“…under the conditions of the present experiments nothing definite was found to justify the use of artificial ionization in general ventilation.”
[3]			X	“They [the experiments] certainly do tend to justify the opinion that, so far as normal subjects are concerned, such effects are unproven and improbable.”
[8]			X	“It was demonstrated that atmospheric ions have an effect on infants, especially those suffering from asthmatic (spastic) bronchitis.” [Note: in some subjects, negative ions had a beneficial impact on bronchial spasms and respiration rate, and positive ions had a deleterious impact in spastic attacks in some normal infants.]
[15]	X			“We concluded that nocturnal administration of negative air ionization has no significant effect upon lung function in the asthmatic child using the above tests.”
[24]	X			“…negative air ions significantly reduced resting values of all physiological variables…these effects tended to disappear under exercise conditions.”
[19]			X	“…no difference in the biologic effect of positive and of negative atmospheric ions…the negative (like the positive) ions did not appear to influence the patient’s typical pattern of wheezing and remission.”
[17]	X			“…twenty-seven patients were exposed to the influence of negative ionization in an experimental room. Many patients with hay fever and asthma responded favorably to the physical alteration of the environment.”
[17]			X	“Favorable responses were elicited by the negative polarity. Positive ionization caused either no relief or increased distress.”
[23]	X			“Negative ion generators are not to be recommended for this problem [sick building syndrome], especially as the data on temperature and humidity provided a good 'internal control' that real effects were being measured.”

*not stated explicitly-presumed negative.