An ion is an atom or molecule with a net electrical charge due to an unequal number of electrons and protons. A positive ion (cation) forms when an atom loses electrons, resulting in a net positive charge. Conversely, a negative ion (anion) forms when an atom gains electrons, giving it a net negative charge. The concept that an excess of positive ions is detrimental to human health has prompted investigation into the validity of this popular belief.
Understanding Positive Ions and Environmental Presence
Positive ions are continuously created in the atmosphere through natural processes, such as the decay of radioactive minerals and the bombardment of air molecules by cosmic rays. These processes dislodge electrons, forming positive ions. Under normal, fair-weather conditions, the concentration of positive ions is typically between 250 and 1,500 ions per cubic centimeter.
Positive ion concentrations are higher in certain environments. Polluted urban air, industrial zones, and enclosed spaces often contain elevated levels due to the presence of large particles like dust, mold, and chemical pollutants. Concentrations sometimes exceed 5,000 ions per cubic centimeter several hours before a thunderstorm or during warm, dry, downslope winds like the Foehn or Santa Ana. Electronic devices, including computers, televisions, and fluorescent lighting, are also common indoor sources of positive ions.
Proposed Biological Interaction with the Human Body
The primary mechanism proposed for the supposed harm from positive ions centers on the body’s neurochemical balance, involving the neurotransmitter serotonin (5-HT). Serotonin is a monoamine neurotransmitter that regulates mood, sleep, and appetite. While found in the central nervous system, approximately 90% of the body’s serotonin is located in the enterochromaffin cells of the gastrointestinal tract.
The serotonin hypothesis suggests that inhaling air with high positive ion concentrations may trigger a rapid release of serotonin in the respiratory tract and the brain. This biochemical change is theorized to overstimulate certain receptors, leading to physiological effects. High concentrations of free serotonin are the proposed chemical link between environmental exposure and negative health responses. This hypothesis posits that positive ions raise serotonin levels, while negative ions reduce them.
Reported Physiological Responses and Symptoms
Proponents of the positive ion theory associate exposure to high concentrations with various negative health outcomes and subjective feelings of discomfort. Symptoms commonly reported include generalized unpleasantness and lethargy. Cognitive effects often cited are mood swings, irritability, difficulty concentrating, and increased anxiety.
Physiological symptoms attributed to high positive ion exposure include headaches, vertigo, and chronic pain. Respiratory issues are also reported, such as acute irritation, dry throat, and the exacerbation of conditions like asthma. Positive ions are also suggested to increase physiological functions such as pulse rate, blood pressure, and metabolic rate, contributing to these unpleasant sensations. These reports align with observations made during warm, dry, high-positive-ion winds, where some people experience heightened health problems.
Scientific Validation and Research Gaps
Despite popular belief and numerous anecdotal reports, scientific evidence supporting the direct harm from ambient positive ions is limited and often conflicting. While the serotonin hypothesis provides a biological framework, comprehensive reviews and meta-analyses have found no consistent influence of positive air ionization on measures of anxiety, mood, relaxation, or personal comfort. Other research supports the “no effect” hypothesis regarding air ions and serotonin concentration or turnover in animal models.
Research into air ionization is challenged by a lack of standardized test conditions, including differences in ion generation methods, concentration measurement, and exposure duration. It is difficult for studies to isolate the effect of ions from other environmental factors that change simultaneously, such as temperature, humidity, and fine particulate pollutants. The scientific consensus is not universal, and the claims that positive ions are definitively harmful are not fully accepted by mainstream medical science. More definitive, well-controlled clinical research is needed to fully understand any potential health impacts.