Abstract
Environmental exposure to phthalates may contribute to an increased risk of asthma in children and adults. We aimed to assess the direction and strength of the association between urinary phthalates metabolites and current asthma in children and adults that participated in the National Health and Nutrition Examination Survey (NHANES) 2007–2012. Data on ten urinary phthalate metabolites, self-reported questionnaires, spirometry measures, and covariates were obtained from 7765 participants (28.1% were children aged 6–17 years) taking part in the NHANES 2007–2012. Asthma was assessed using self-reported questionnaires for children and adults, and via spirometry measures for adults alone. We used crude and adjusted logistic regression models to estimate the odds ratios (ORs) and 95% confidence interval (CI) per one log10 unit change in the concentration of phthalate metabolites. We further modeled the effect modification by sex. Out of 10 metabolites, only mono-benzyl phthalate (MBzP) was positively associated with the prevalence of self-reported asthma in children, after adjusting for a range of potential confounders (odds ratio 1.54; 95% confidence interval 1.05–2.27). No significant relationship was observed for adults. The association of mono-ethyl phthalate (MEP) was modified by sex, with significantly increased odds of asthma among males [boys (2.00; 1.14–3.51); adult males (1.32; 1.04–1.69)]. While no other phthalates showed a positive relationship with current asthma in males, mono-(carboxynonyl) phthalate (MCNP) and mono-(3-carboxylpropyl) phthalate (MCPP) were inversely associated with spirometrically defined asthma in adult females. A sex-specific relationship in adults was evident when spirometry, but not self-reported measures were used to define asthma. We found no clear association between exposure to phthalates and current asthma, except for a significant relationship between MBzP metabolites and self-reported asthma in children. As a result, exposure to phthalates and asthma development and/or exacerbations remains controversial, suggesting a need for a well-designed longitudinal study.
Highlights
For the past two decades, the prevalence of asthma has substantially increased in both the developed and developing countries (Osborne et al 2017)
Urinary phthalate concentrations were determined for 7765 subsets (2180 children and 5585 adults); only these participants were used for analysis
The weighted proportions of all children belonging to any race or living below the poverty threshold [povertyto-income ratio (PIR)] were somewhat similar to those with measured phthalate metabolites
Summary
For the past two decades, the prevalence of asthma has substantially increased in both the developed and developing countries (Osborne et al 2017). Asthma is a common chronic disease in children and adults characterised by airway inflammation and increased mucus production—leading to airway obstruction (Khalili et al 2018). It is estimated by the US Centers for Disease Control and Prevention (CDC) that 6.8% of US working adults have current asthma—defined as having had at least one asthma attack or visit the emergency department (ED) for asthma in the past 12 months (Mazurek and Syamlal 2018). The root causes of asthma have not been fully elucidated, but genetic predisposition, and environmental factors including allergens and chemicals (such as phthalates) as well as geneenvironment interactions, have been suggested as important risk factors for asthma pathogenesis and exacerbations (Wang et al 2015; Sordillo et al 2015; Surdu et al 2006)
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