1. Formaldehyde is a naturally occurring VOC found in small amounts in animals and plants but is carcinogenic and an irritant to most people when present in high concentrations, causing headaches, dizziness, mental impairment, and other symptoms. When present in the air at levels above 0.1 ppm, it can cause watery eyes; burning sensations in the eyes, nose, and throat; nausea; coughing; chest tightness; wheezing; skin rashes; and asthmatic and allergic reactions.2. A known carcinogen with no known safe exposure level. Formaldehyde occurs naturally, but appears in unnaturally high concentrations in many buildings because it is an ingredient in binders used in many building materials and furnishings.