A Comprehensive Literature Review on the Effects of Formaldehyde on the Upper Respiratory Tract

Abstract

Prolonged exposure to indoor air pollutants at high concentrations can have adverse health effects on the respiratory system of individuals who spend most of their time indoors. Formaldehyde (FA) is a common indoor air pollutant because of its extensive use in household products such as cleaners, floorings, and furnishings. As a chemical, FA is highly water soluble and reactive. When its airborne form is inhaled, it is mainly absorbed in the upper airways. FA has been extensively studied for its carcinogenic effects, but it can also cause inflammation in the upper airways. The objective of the current review was to assess the secondary effects of such inflammation and how it can contribute to an increased risk for upper respiratory infections, which are mostly caused by viruses. A rigorous literature review was conducted through gathering, reading, and analyzing relevant literature, including peer-reviewed articles published after 1990 and seminal literature regardless of publication date. Findings from the review provide a greater understanding of the outcomes of FA exposure, the potential accumulative damage to the upper respiratory tract, and the associated increased risk for acute infections of the upper respiratory tract. This information can help in the development and enforcement of stricter regulations for furniture and building materials for household-related products to limit exposure to indoor pollutants such as FA.

Keywords: formaldehyde exposure; histopathological findings; indoor air pollution; mucociliary clearance; respiratory epithelium; upper respiratory tract; upper respiratory tract infection.

Figure 1. Chronic cycle of inflammation secondary to formaldehyde. Created by authors using BioRender.

URT: upper respiratory tract

Figure 2. Methodology diagram of literature review study. Created by authors using BioRender.

Figure 3. Graphic that summarizes significant findings of the studies. Created by authors using BioRender.

FM: formaldehyde; MC: mucociliary clearance; CBF: ciliary beat frequency; HMMECs: human mucosal microvascular endothelial cells; ECP: eosinophil cationic protein