It is difficult to determine which pollutant or pollutants are the sources of a person’s ill health, or even if indoor air pollution is the problem. Many indoor air pollutants cannot be detected by our senses (e.g., smell) and the symptoms they produce can be vague and sometimes similar, making it hard to attribute them to a specific cause. Some symptoms may not show up until years later, making it even harder to discover the cause. Common symptoms of exposure to indoor air pollutants include headaches, tiredness, dizziness, nausea, an itchy nose, and a scratchy throat. More serious effects are asthma and other breathing disorders and cancer.