Ortho-Phthalaldehyde (OPA) has been approved for high-level sterilization of heat-sensitive
medical instruments and is increasingly being used as a replacement in the healthcare industry
for glutaraldehyde, a known sensitizer. Numerous case reports have been published indicating
workers and patients experiencing respiratory problems, anaphylaxis, skin reactivity, and
systemic antibody production. Our laboratory previously demonstrated that OPA is a dermal
sensitizer in mice. The goal of the present study was to determine if OPA is a respiratory
sensitizer following inhalation exposure. Mice were exposed to OPA vapor and airway and
lymph nodes were examined for cytokine gene expression and alterations in lymphocyte
populations. Inhalation of OPA for 3 days resulted in a concentration-dependent increase in
lymphocyte proliferation, mainly B lymphocytes, in the draining lymph nodes. A secondary
challenge of mice with OPA resulted in a dramatic increase in the population of B lymphocytes
expressing IgE. Expression of Th2 (IL-4, IL-5, and IL-13) and anti/proinflammatory (IL-10,
TNFα, and IL-1β) cytokine genes was upregulated in the lymph nodes and the nasal mucosa.
Mice exposed to the higher concentrations of OPA-produced OPA-specific IgG1 antibodies
indicating systemic sensitization. These findings provide evidence that OPA has the potential to
cause respiratory sensitization in mice.
Inhalation of Ortho-Phthalaldehyde Vapor Causes Respiratory Sensitization in Mice