Impacts of low socioeconomic status and polycyclic aromatic hydrocarbons exposure on lung function among a community-based Chinese population

Developing a profile of urinary PAH metabolites among Chinese populations in the 2010s

Polycyclic aromatic hydrocarbons (PAHs) pose significant health risks. However, no nationwide cohort has been established to consistently record biomonitoring data on PAH exposure in the Chinese population. Biomonitoring data from 56 published studies were combined in this study to develop a profile of urinary PAH metabolites among Chinese population in the 2010s. The stacked column charts described the composition profiles of hydroxylated PAHs (OH-PAHs) in general, special, and occupational populations. Hydroxynaphthalene (OH-Nap) and hydroxyfluorene (OH-Flu) accounted for more than half of the urinary OH-PAH in general and special populations. The urine of the occupational populations contained a significant amount of hydroxyphenanthrene (OH-Phe) and 1-hydroxypyrene (1-OHPyr). Furthermore, this study analyzed the distribution profiles of non-occupationally exposed populations, such as spatial distribution, age distribution, and trends over time. The population of the Southern region had higher urinary OH-PAH concentrations than the population of the Northern region. Adults (45-55 years old) had the highest level of internal PAH exposure. Between 2010 and 2018, the overall trend of urinary OH-PAHs in Chinese general populations decreased. The cumulative distribution function (CDF) revealed that 1-OHNap and 1-OHPyr were better at distinguishing internal PAH exposure among different populations. The sum of OH-Flu and OH-Phe in urine can be used to assess the impact of indoor and outdoor environments on human exposure to PAHs. Our findings suggest that more emphasis should be placed on collecting biomonitoring data for adults of all ages (particularly in the Northern region) and vulnerable populations. In conclusion, this study advocates for the establishment of a nationwide cohort study of Chinese populations as soon as possible in the future to evaluate the Chinese population's exposure to environmental contaminants.

Systematic Review of Exposure to Polycyclic Aromatic Hydrocarbons and Obstructive Lung Disease

BACKGROUND

There is fast-growing epidemiologic evidence of the effects of environmental chemicals on respiratory health. Polycyclic aromatic hydrocarbons (PAHs) have been linked with airway obstruction common in asthma and/or asthma exacerbation, and chronic bronchitis and emphysema.

OBJECTIVES

A systematic review of the association between exposure to PAHs and obstructive lung diseases is not yet available. The present systematic review aims to evaluate the evidence available in epidemiological studies that have associated PAHs with obstructive lung diseases such as asthma, chronic bronchitis, emphysema.

METHODS

We performed a systematic literature search on PubMed, Google Scholar, and Scopus databases using relevant keywords and guided by predesigned eligibility criteria.

RESULTS

From the total of 30 articles reviewed, 16 articles examined the link between PAHs and lung function in both adults and children. Twelve articles investigated the association between PAHs and asthma, asthma biomarkers, and/or asthma symptoms in children. Two articles studied the relationship between PAHs and fractional exhaled nitric oxide (FeNO), a biomarker of airway inflammation and the relationship between PAHs and obstructive lung diseases and infections, respectively. One study assessed exposure to daily ambient PAHs and cough occurrence.

DISCUSSION

Twenty-seven studies found an association between PAHs and asthma and reduced lung function. In children it is reinforced by studies on prenatal and postnatal exposure, whereas in adults, reductions in lung function tests marked by low forced expiratory volume in 1 second, (FEV₁), forced vital capacity (FVC), and forced expiratory flow (FEF_25-75%) were the major health outcomes. Some studies recorded contrasting results: insignificant and/or no association between the two variables of interest. The studies reviewed had limitations ranging from small sample size, to the use of cross-sectional rather than longitudinal study design.

CONCLUSIONS

The literature reviewed in the present study largely suggest positive correlations between PAHs and obstructive lung diseases marked mainly by asthma and reduced respiratory function. This review was registered with PROSPERO (Registration no: CRD42020212894).

COMPETING INTERESTS

The authors declare no competing financial interests.

Potential role of polycyclic aromatic hydrocarbons in air pollution-induced non-malignant respiratory diseases

Epidemiological studies have found strong associations between air pollution and respiratory effects including development and/or exacerbation of asthma and chronic obstructive pulmonary disease (COPD) as well as increased occurrence of respiratory infections and lung cancer. It has become increasingly clear that also polycyclic aromatic hydrocarbons (PAHs) may affect processes linked to non-malignant diseases in the airways. The aim of the present paper was to review epidemiological studies on associations between gas phase and particle-bound PAHs in ambient air and non-malignant respiratory diseases or closely related physiological processes, to assess whether PAH-exposure may explain some of the effects associated with air pollution. Based on experimental in vivo and in vitro studies, we also explore possible mechanisms for how different PAHs may contribute to such events. Epidemiological studies show strongest evidence for an association between PAHs and asthma development and respiratory function in children. This is supported by studies on prenatal and postnatal exposure. Exposure to PAHs in adults seems to be linked to respiratory functions, exacerbation of asthma and increased morbidity/mortality of obstructive lung diseases. However, available studies are few and weak. Notably, the PAHs measured in plasma/urine also represent other exposure routes than inhalation. Furthermore, the role of PAHs measured in air is difficult to disentangle from that of other air pollution components originating from combustion processes. Experimental studies show that PAHs may trigger various processes linked to non-malignant respiratory diseases. Physiological- and pathological responses include redox imbalance, oxidative stress, inflammation both from the innate and adaptive immune systems, smooth muscle constriction, epithelial- and endothelial dysfunction and dysregulated lung development. Such biological responses may at the molecular level be initiated by PAH-binding to the aryl hydrocarbon receptor (AhR), but possibly also through interactions with beta-adrenergic receptors. In addition, reactive PAH metabolites or reactive oxygen species (ROS) may interfere directly with ion transporters and enzymes involved in signal transduction. Overall, the reviewed literature shows that respiratory effects of PAH-exposure in ambient air may extend beyond lung cancer. The relative importance of the specific PAHs ability to induce disease may differ between the biological endpoint in question.

Air pollution inequality and health inequality in China: An empirical study

China's residents experience unequal exposure to air pollution in different regions, and the corresponding health consequences have increased remarkably. To ensure sustainable development, China should monitor health inequality and its potential determinants. This study empirically examines the health inequalities (represented by perinatal and tuberculosis mortalities) caused by air pollution inequalities (represented by SO₂ and NO_x emissions) from 31 Chinese provinces in the period 2006 to 2015, using the generalized method of moments (GMM) and quantile regression (QR). The GMM results reveal a strong positive relationship between SO₂/NO_x emission inequality and tuberculosis mortality inequality. In contrast, the QR results show that perinatal mortality inequality is closely related to emission inequality across all percentiles for SO₂ emission and at the 75th percentile for NO_x emission. Our findings help policymakers to identify health disparities and be mindful of air pollution inequality as a factor in the elimination of health inequality.

Declining Pulmonary Function in Populations with Long-term Exposure to Polycyclic Aromatic Hydrocarbons-Enriched PM2.5

This study assesses the effects of long-term exposure to ambient air pollutants on inflammatory response and lung function. We selected 390 male coke oven workers with exposure to polycyclic aromatic hydrocarbons (PAHs) and fine particulate matter (PM_2.5) and 115 control workers. The average duration in the exposed group was 9.10 years. The total amount of PAHs was more enriched in PM_2.5 which collected from the coke oven workshops compared with the control areas. Correspondingly, the internal PAHs exposure indicated by urinary 1-hydroxypyrene (1-OHP) in the exposure group increased 25.7-fold compared to that of the control group. Moreover, the increasing level of urinary 1-OHP was associated with the decrease of forced expiratory volume in 1 s to forced vital capacity ratio (FEV₁/FVC). In non-current smokers of exposure group, inverse correlation of 1-OHP with FEV₁/FVC was also found. Particularly, an exposure duration-dependent decline in FEV₁/FVC and mean forced expiratory flow between 25% and 75% of forced vital capacity (FEF_25-75%) indicated that small airways were functionally obstructed. Furthermore, the increasing serum high-sensitivity C-reactive protein (hs-CRP) was correlated with the decline in pulmonary function in all subjects. These findings provide a clue that long-term exposure to PAHs-enriched PM_2.5 impairs pulmonary function in occupational population.