Raised exhaled nitric oxide in healthy children is associated with domestic formaldehyde levels

Exposure to domestic levels of formaldehyde has been associated with adverse respiratory symptoms in both adults and children. The underlying mechanisms responsible for these findings have not been established. In order to investigate possible inflammatory effects of formaldehyde at levels typically found in the home, we measured exhaled nitric oxide (eNO) in 224 healthy children 6 to 13 yr of age (116 girls) and monitored formaldehyde levels in their homes. Formaldehyde was monitored using a passive sampling technique. Exhaled NO was measured directly into a fast response chemiluminescence nitric oxide analyzer. The children also undertook a lung function (spirometry) test. There was no effect of formaldehyde levels measured in homes on spirometric variables. However, eNO levels were significantly elevated in children living in homes with average formaldehyde levels ⩾ 50 ppb. Exhaled NO levels (geometric mean) were 15.5 ppb (95% CI: 10.5 to 22.9 ppb) for children from homes with formaldehyde concentrations ⩾ 50 ppb compared with 8.7 ppb (7.9 to 9.6) for children from homes with formaldehyde concentrations < 50 ppb (p < 0.05). These results suggest that exposure to formaldehyde in homes may invoke a subclinical inflammatory response in the airways of healthy children. Formaldehyde is a common air pollutant in homes. It is highly irritant to the mucous membranes and its effect on the eyes and upper respiratory tract is well documented (1). In the workplace, exposure to formaldehyde has been implicated in occupational asthma (2) and, recently, domestic exposure has been associated with lower respiratory tract symptoms and disease in both children (3-5) and adults (6, 7). Specific mechanisms to account for these findings have not yet been identified; however, it is possible that formaldehyde may have a direct toxic effect on the respiratory epithelium, inducing inflammatory reactions (8). Inflammatory changes are observed in the upper airways after acute low level exposure to formaldehyde (9), and damage to the lower airways is reported after exposure to high levels (5 to 30 ppm) (1). The inflammatory effects of chronic low level exposure on the lower airways, however, have not been well researched. The aim of the present study was to investigate the possible inflammatory effects of formaldehyde concentrations typically encountered in the domestic environment. Nitric oxide (NO) measured from the exhaled breath of children was used as a marker of airway inflammation