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.

Viral respiratory infections (VRIs) can spread quickly and cause enormous morbidity and mortality worldwide. These events pose serious threats to public health due to time lags in developing vaccines to activate the acquired immune system. The high variability of people’s symptomatic responses to viral infections, as illustrated in the current COVID-19 pandemic, indicates the potential to moderate the severity of morbidity from VRIs. Growing evidence supports roles for probiotic bacteria (PB) and prebiotic dietary fiber (DF) and other plant nutritional bioactives in modulating immune functions. While human studies help to understand the epidemiology and immunopathology of VRIs, the chaotic nature of viral transmissions makes it difficult to undertake mechanistic study where the pre-conditioning of the metabolic and immune system could be beneficial. However, recent experimental studies have significantly enhanced our understanding of how PB and DF, along with plant bioactives, can significantly modulate innate and acquired immunity responses to VRIs. Synbiotic combinations of PB and DF potentiate increased benefits primarily through augmenting the production of short-chain fatty acids (SCFAs) such as butyrate. These and specific plant polyphenolics help to regulate immune responses to both restrain VRIs and temper the neutrophil response that can lead to acute respiratory distress syndrome (ARDS). This review highlights the current understanding of the potential impact of targeted nutritional strategies in setting a balanced immune tone for viral clearance and reinforcing homeostasis. This knowledge may guide the development of public health tactics and the application of functional foods with PB and DF components as a nutritional approach to support countering VRI morbidity.

Formaldehyde is a highly irritant gas commonly encountered in indoor environments. Domestic levels of formaldehyde may vary with building practices and climate and the aim of the present study was to investigate formaldehyde levels in 185 homes in Perth, Australia. The formaldehyde was monitored using a validated passive sampling technique. Levels were measured in four rooms of each house (living room, kitchen and large and small bedrooms). In 160 homes the monitoring was repeated 4–7 months later in a different season to the original measurement. It was found that within homes there was no significant difference in formaldehyde concentrations measured in the four rooms. For the first sampling period, the geometric mean of the average household concentration (average of the four rooms) for all homes was 22.8 ppb and ranged from 3.0 to 92.3 ppb. Only the age of the house (p < 0.0001) and the season of monitoring (p < 0.0001) were significant predictors of indoor levels, higher levels in newer homes and in homes monitored in summer. Mean concentrations were lower during the follow-up monitoring, but only in houses that were less than 10 years old or in houses that were initially monitored in summer. Overall formaldehyde concentrations were low and rarely exceeded the Australian guideline level of 100 ppb. There seemed to be good inter-room mixing of formaldehyde within homes. Concentrations were significantly affected by season and age of the house.

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