US EPA Toxicology Review of Formaldehyde Confirms the California Health Assessment

The EPA considered seven studies for its review. All of these were epidemiological studies of people, and several included children and asthmatics. Scientists derived candidate inhalation reference concentrations (RfCs) for chronic exposures related to sensory irritation, decreased pulmonary function in children, increased asthma incidence in children, increased allergic sensitization to common allergens in children, and decreased time to pregnancy in women. Three studies were particularly relevant.

When the symptoms of respiratory effects/asthma and sensitization are considered, the derived RfCs range from 2.8 to 11 ppb. The study suggests that the average or median value could be selected, resulting in an air concentration of about 6 ppb, or 7.4 micrograms per cubic meter (mg/m³). This value is comparable to the California OEHHA 8-hour and chronic Reference Exposure Level of 9 mg/m³. An RfC based on irritation alone would be higher, in the range of 17 to 70 mg/m³.

In addition, the study developed a unit risk estimate for cancer associated with nasalpharyngeal cancer, Hodgkin lymphoma and leukemia combined. The upper bound unit risk based on adult human data was estimated to be 6.6 x 10^-5 per mg/m³. Applying age-dependent adjustment factors for increased early-life susceptibility, the overall combined cancer unit risk for a lifetime exposure was estimated to be 1.1 x 10^-4 per mg/m³.