Acute airway narrowing in monkeys from challenge with 2.5 ppm formaldehyde generated from formalin

Nine adult male Cynomolgus monkeys (Macaca fascicularis) were exposed for 10 min to 2.55 +/- 0.03 ppm formaldehyde (HCHO; mean +/- standard error of the mean, SEM) generated from formalin with a newly developed HCHO challenge system. The generation system was capable of producing highly stable HCHO vapor concentrations with fluctuations of HCHO concentrations of less than +/- 5%. The experimental design included pre-exposure methacholine challenge to determine if responses to HCHO were associated with pre-existing bronchial hyperreactivity. Significant changes in average pulmonary flow resistance (RL) were observed (compared to control RL values) at 2 (p less than 0.01), 5 (p less than 0.01), and 10 min (p less than 0.005) post-HCHO challenge. Pre-challenge RL values (mean +/- SEM) were 11.3 +/- 1.4 cm H2O.l/s, while at 2, 5, and 10 min after HCHO challenge, values were 16.1 +/- 2.1, 16.9 +/- 2.8 and 20.0 +/- 3.4 cm H2O.l/s, respectively. Methacholine challenge data suggest that reactions to HCHO tend to be greater in monkeys hyperreactive to methacholine, but the relationship does not reach statistical significance in this small series of animals. These data indicate that significant pulmonary function deficits occur immediately after challenge with 2.55 ppm HCHO vapor in monkeys.