Particulate Matter Exposure and Stress Hormone Levels

Abstract

BACKGROUND:Exposure to ambient particulate matter (PM) is associated with a number of adverse health outcomes, but potential mechanisms are largely unknown. Metabolomics represents a powerful approach to study global metabolic changes in response to environmental exposures. We therefore conducted this study to investigate changes in serum metabolites in response to the reduction of PM exposure among healthy college students. METHODS:We conducted a randomized, double-blind crossover trial in 55 healthy college students in Shanghai, China. Real and sham air purifiers were placed in participants' dormitories in random order for 9 days with a 12-day washout period. Serum metabolites were quantified by using gas chromatography-mass spectrometry and ultrahigh performance liquid chromatography-mass spectrometry. Between-treatment differences in metabolites were examined using orthogonal partial least square-discriminant analysis and mixed-effect models. Secondary outcomes include blood pressure, corticotropin-releasing hormone, adrenocorticotropic hormone, insulin resistance, and biomarkers of oxidative stress and inflammation. RESULTS:The average personal exposure to PMs with aerodynamic diameters ≤2.5 μm was 24.3 μg/m 3 during the real purification and 53.1 μg/m 3 during the sham purification. Metabolomics analysis showed that higher exposure to PMs with aerodynamic diameters ≤2.5 μm led to significant increases in cortisol, cortisone, epinephrine, and norepinephrine. Between-treatment differences were also observed for glucose, amino acids, fatty acids, and lipids. We found significantly higher blood pressure, hormones, insulin resistance, and biomarkers of oxidative stress and inflammation among individuals exposed to higher PMs with aerodynamic diameters ≤2.5 μm. CONCLUSIONS:This study suggests that higher PM may induce metabolic alterations that are consistent with activations of the hypothalamuspituitary-adrenal and sympathetic-adrenal-medullary axes, adding potential mechanistic insights into the adverse health outcomes associated with PM. Furthermore, our study demonstrated short-term reductions in stress hormone following indoor air purification. ORIGINAL RESEARCH ARTICLE C onvincing epidemiological evidence suggests that exposure to higher levels of ambient particulate matters (PMs), especially fine PMs with aerodynamic diameters ≤2.5 μm (PM 2.5 ), may have adverse cardiovascular and metabolic consequences such as hypertension, coronary heart disease, stroke, and diabetes mellitus. CLINICAL TRIAL REGISTRATION:1-4 Although potential biological mechanisms for these adverse health effects are yet to be fully ascertained, inflammation and oxidative stress are likely to be involved. [5][6][7] In addition, several studies have reported an association between PM exposure and dysfunction of the automatic nervous system, which is known to increase cardiovascular risk. [8][9][10] Animal studies further implicated PM 2.5 as a stressor to the central nervous system that might induce a cascade of neuroendocrine responses...

Risk Reduction Behaviors Regarding PM2.5 Exposure among Outdoor Exercisers in the Nanjing Metropolitan Area, China

“…Therefore, it may not be one of the most efficient ways to reduce PM 2.5 exposure. The current studies showed that air purifiers could result in significant reduction in indoor PM 2.5 concentration and improve human health in some areas with ambient particulate air pollution [44,45]. Two randomized, double-blind cross over trials among Chinese college students suggested clear cardiopulmonary benefits of indoor air purification [44,45].…”

“Stressed” About Air Pollution

“…The findings by Li et al 7 also add to the growing body of evidence that simple interventions such as air purifier systems using high-efficiency particulate arrestance filters can help protect against adverse health impacts of air pollution. 5,13 The reduction in estimated PM 2.5 exposure afforded by filtration favorably influenced most of the health outcomes (blood pressure, insulin resistance, oxidative stress, inflammation), curtailed PM 2.5 -induced activation of the sympathetic nervous system and hypothalamic-pituitary-adrenal axis, and helped mitigate the ensuing metabolomic perturbations.…”

“…In this issue, Li et al 7 have provided some significant insights into both of these issues. In a well-designed randomized, double-blind, crossover trial using indoor air purifiers, the investigators demonstrated that short-term exposure (9 days) to high levels of ambient PM 2.5 (outdoor mean, 101 μg/m 3 ) among 55 healthy young students in Shanghai prompted a host of adverse cardiometabolic responses.…”

Response by Li et al to Letters Regarding Article, “Particulate Matter Exposure and Stress Hormone Levels: A Randomized, Double-Blind, Crossover Trial of Air Purification”

“…Unfortunately, we did not measure total PM and ultrafine particles in the study because initially our primary exposure of interest was PM with aerodynamic diameters ≤2.5 μm, and thus we were not able to conclude whether the observed health benefits were because of the reduction of PM 2.5 or ultrafine particles. 1 Third, although melatonin may have cardioprotective effects because of its antioxidative property in experimental settings, evidence in humans are not consistent. For instance, Dominguez-Rodriguez et al 2 found no beneficial effects on cardiovascular system in patients with ST-elevation myocardial infarction.…”