Association between indoor formaldehyde exposure and asthma: A systematic review and meta‐analysis of observational studies

Abstract

About 339 million people worldwide are suffering from asthma. We aimed to investigate whether exposure to formaldehyde (FA) is associated with asthma, which could provide clues for preventive and mitigation actions. This article provides a systematic review and meta‐analysis of observational studies to assess the association between indoor FA exposure and the risk of asthma in children and adults. An electronic search of PubMed, Embase, and Web of Science was performed to collect all relevant studies published before January 1, 2020, and a total of 13 papers were included in this meta‐analysis. A random‐effect model was conducted to calculate the pooled odds ratio (OR) between FA exposure and asthma. We found that each 10 µg/m3 increase in FA exposure was significantly associated with a 10% increase in the risk of asthma in children (OR = 1.10, 95% confidence interval = 1.00‐1.21). We sorted the FA concentrations reported in the selected articles and categorized exposure variables into low (FA ≤ 22.5 µg/m3) and high exposure (FA > 22.5 µg/m3) according to the median concentration of FA. In the high‐exposure adult group, FA exposure may also be associated with an increased risk of asthma (OR = 1.81, 95% CI = 1.18‐2.78).

Challenges and recommendations on the conduct of systematic reviews of observational epidemiologic studies in environmental and occupational health

“…Despite these flaws, this scale continues to be widely used in published reviews ( 24 ). A recent systematic review and meta-analysis on indoor formaldehyde exposure and asthma utilized the Newcastle-Ottawa Scale for case-control and cohort studies ( 25 ). In this study, no information was provided by the authors as to why each study scored the way it did, leading to a lack of transparency in their risk-of-bias findings.…”

Network-based integrated analysis for toxic effects of high-concentration formaldehyde inhalation exposure through the toxicogenomic approach

“…Inhaled formaldehyde mainly affects the upper respiratory system, but a certain amount can be deposited directly into the lower respiratory system during oronasal breathing 2 . In animal, epidemiologic, and pulmonary function test studies, inhaled formaldehyde caused respiratory symptoms, with asthma identified as one of the most common diseases to arise due to exposure in indoor and occupational environments 25 – 29 . However, detailed knowledge of the mechanisms of respiratory disease onset associated with genetic changes in response to formaldehyde exposure is still lacking.…”

Housing conditions and respiratory morbidity in Indigenous children in remote communities in Northwestern Ontario, Canada

“…We logged particulate matter 2.5 (PM 2.5 ) concentrations by laser photometry and an in-line filter to collect corresponding gravimetric measurements. We also analyzed filters for levoglucosan, 10,[17][18][19][20] a major constituent of wood smoke. 21 We used a carbon dioxide (CO 2 ) sensor attached to a data logger to measure CO 2 , with a second logger to collect temperature and relative humidity (RH).…”