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Table 1 Summary of quality ratings of studies reviewed

From: Exposure of laboratory animals to small air ions: a systematic review of biological and behavioral studies

Topic Number of studiesa Number of studies in compliance with quality indicatorsb
Shamcontrol Confoundingbc Blinding Randomized Individual exposure
Behavior 13 12 6 4 4 6
Learning and memory 9 4 2 1 5 3
Serotonin and other neurotransmitters 13 6 2 4 6 4
Tracheal function 7 6 2 0 0 3
Respiratory infection 5 4 1 0 2 0
Cardiovascular measures 5 4 0 0 0 5
Reproduction and growth 11 8 3 0 3 1
Carcinogenesis 2 1 0 0 1 1
Other endpoints 4 2 1 0 1 1
Totals (%) 69 47 (68%) 22(35%) (32%) 9 (13%) 22 (32%) 24 (35%)
  1. aSome of the 62 studies reported results in more than 1 topic area
  2. bSome studies that did not generate air ions by corona discharge were not susceptible to major confounding factors
  3. cMinimal compliance was indicated if any confounding factor, electric field, ozone, noise, or light was addressed