Formaldehyde Exposure and Asthma in Children: A Systematic Review

Gerald McGwin Jr.; Jeffrey Lienert; John I. Kennedy Jr.

Disclosures

Environ Health Perspect. 2010;118(3) 

In This Article

Abstract and Introduction

Abstract

Objective: Despite multiple published studies regarding the association between formaldehyde exposure and childhood asthma, a consistent association has not been identified. Here we report the results of a systematic review of published literature in order to provide a more comprehensive picture of this relationship.
Data sources: After a comprehensive literature search, we identified seven peer-reviewed studies providing quantitative results regarding the association between formaldehyde exposure and asthma in children. Studies were heterogeneous with respect to the definition of asthma (e.g., self-report, physician diagnosis). Most of the studies were cross-sectional.
Data extraction: For each study, an odds ratio (OR) and 95% confidence interval (CI) for asthma were either abstracted from published results or calculated based on the data provided. Characteristics regarding the study design and population were also abstracted.
Data synthesis: We used fixed- and random-effects models to calculate pooled ORs and 95% CIs; measures of heterogeneity were also calculated. A fixed-effects model produced an OR of 1.03 (95% CI, 1.021.04), and random effects model produced an OR of 1.17 (95% CI, 1.011.36), both reflecting an increase of 10 µg/m3 of formaldehyde. Both the Q and I 2 statistics indicated a moderate amount of heterogeneity.
Conclusions: Results indicate a significant positive association between formaldehyde exposure and childhood asthma. Given the largely cross-sectional nature of the studies underlying this meta-analysis, further well-designed prospective epidemiologic studies are needed.

Introduction

Acute exposure to formaldehyde can cause eye, nose, throat, and skin irritation, whereas long-term exposure has been associated with certain cancers (e.g., sinonasal) as well as asthma (Daisey et al. 2003). Exposure to formaldehyde occurs in certain occupational settings (e.g., embalmers), but exposure via formaldehyde-emitting products such as particle board, urea formaldehyde insulation, carpeting, and furniture is more common (Garrett et al. 1999). In the United States, the legal occupational limit for short-term (i.e., < 15 min) formaldehyde exposure is 2 ppm, and the long-term limit (i.e., > 15 min) is 0.75 ppm [Occupational Safety and Health Administration (OSHA) 2005]. In contrast, the National Institute for Occupational Safety and Health suggests that exposure be limited to much lower levels: 0.016 ppm (long term) and 0.1 ppm (short term).

Much of the research regarding the health effects of formaldehyde has focused on cancer, whereas less attention has been paid to more common conditions such as asthma. In the United States, the prevalence of asthma is approximately 7% among adults and 9% among children (Akinbami et al. 2009; Moorman et al. 2007). Among adults, some studies have reported a positive association between formaldehyde and asthma (Wieslander et al. 1997), while others have not (Krzyzanowski et al. 1990). It has been suggested that certain groups, specifically children, may be particularly sensitive to formaldehyde exposure; however, as with adults, the results have been inconsistent, with some studies reporting an association (Garrett et al. 1999) and others not (Symington et al. 1991). All of these studies have specific limitations including small sample sizes (Delfino et al. 2003), the use of self-reported asthma (Smedje et al. 1997), and potential selection bias (Garrett et al. 1999). In addition, the extent of formaldehyde exposure varies widely across studies. For example, Mi et al. (2006) reported a range of 320 µg/m3, whereas the range reported by Rumchev et al. (2002) was ~ 0224 µg/m3. However, the former study derived measurements from schools while the latter study obtained measurements from homes. Moreover, most studies are cross-sectional and fail to provide information on exposure levels that reflect individual exposure (in magnitude and/or duration).

Although there have been multiple reviews of the literature pertaining to formaldehyde and asthma in children, these have all been qualitative (Mendell 2007). The relationship between formaldehyde and respiratory symptoms has received attention recently because of concerns regarding air quality in mobile homes and travel trailers provided by the Federal Emergency Management Agency (FEMA) to displaced Gulf Coast residents in the aftermath of Hurricane Katrina. We conducted the current study, a systematic review of the literature regarding the potential association between formaldehyde exposure and asthma in children, to shed additional light on the issue.

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