Abstract
Environmental intolerance (EI) is a chronic acquired disorder characterized by non-specific and recurrent multisystem symptoms attributed to low levels of chemical, biologic, or physical agents. Multiple chemical sensitivity (MCS) or chemical intolerance (CI) is one of the EI. This review presents the suggested mode of action, pathophysiology, epidemiology, and extrinsic environmental factors for preventing MCS/CI. Patients with MCS process odors differently from healthy controls. Several studies suggested that patients with MCS were demonstrated to peculiarly react to sensory stimuli, with activation of brain areas connected with motivational and emotional processing of the information. These brain responses may involve cognitive and memory processing systems during past exposure event to harmful chemicals. A 5-year follow-up epidemiological study indicated that the baseline negative psychosomatic states, including irritability, fatigue, anxiety, depressed mood, and somatic symptoms were associated with development of CI in controls. Appropriate physical activity and maintaining a regular lifestyle, including diet or sleep, were factors for improvement of CI in the CI group. Stable psychosomatic state is essential for preventing CI. Multiple extrinsic environmental factors involve the onset of MCS/CI and the exposure events are different in patients with MCS. In particular, information on the exposure concentration is very limited. Many countries including Japan have developed air quality guidelines or standards in indoor, ambient, or occupational environment. These provide a uniform basis for protecting public health from the adverse effects of air pollution, and to eliminate or reduce to a minimum exposure to those pollutants that are known or are likely to be hazardous to human health. Furthermore, these guidelines or standards can serve to limiting emissions, especially those of materials, products, or industrial activities. These guidelines or standards will play an important role in preventing the onset of MCS/CI. Continuous assessment and management in indoor, ambient, and occupational environment are required.
