Multiple Chemical Sensitivity (MCS) is a health problem where sensitive people– some studies show up to 30% of the general population– react unfavorably to very low levels of synthetic chemicals in the environment from things like pesticides, cigarette smoke, paint fumes, wood preservatives, photocopier fumes, perfumes and epoxy. Symptoms vary from fleeting to severe and might include rapid heart rate, shortness of breath, fatigue, flushing, dizziness, nausea, coughing, or difficulty concentrating (reference).
People with MCS are often call “canaries.” The name comes from an old practice of miners who took canaries with them into the mines; if the canary died from toxic air in the shaft, the miners had time to escape with their lives. People with chemical sensitivities are the canaries of the modern world.
This is excerpt from article on The Canary Report.