Formaldehyde as an Air Toxic: Indoor and Outdoor Exposure and Risk

Formaldehyde is a chemical used in industrial processes and found in household products such as wood products and adhesives. It is also a secondary product of photooxidation in the atmosphere. It is listed as a probable human carcinogen or a known human carcinogen, and acute and chronic exposure can lead to respiratory health effects, eye, nose, and throat irritation, and allergic sensitization (Formaldehyde). This study aims to characterize population risk due to formaldehyde inhalation exposure both in the home and outdoors. Indoor and outdoor concentrations were measured from six houses in Pullman, WA and Tri Cities, WA as part of an EPA Indoor Air Quality study (EPA IAQ). These were compared to three outdoor sites in the Lewiston-Clarkston Valley (LCV), a region being monitored in an air toxics study for elevated levels of formaldehyde. EPA’s Integrated Risk Information System (IRIS) was used to perform risk characterization. Analysis of the homes showed an indoor median expected excess of 269-801 cancers per million, while the outdoor data ranged from 24-61 excess cancers per million. The three monitored sites in the LC Valley had median risks of 27.03, 35.13, and 43.70. Additionally, outdoor formaldehyde levels in the LCV appeared to be correlated to the Clearwater Pulp and Paper Mill, while indoor pollution was variable and may depend on habits and products in the home. Data analysis indicated that even in relatively polluted areas, ambient HCHO levels do not appear to pose a significant risk to human health as compared to indoor air. While outdoor point source pollution is regulated, indoor air pollution is not monitored for safety. Qualitative GC-MS analysis was done on indoor air samples to better understand what abundant organic species are contributing to indoor air pollution.