An Ecological Study of the Association of Metal Air Pollutants with Lung Cancer Incidence in Texas

Composition analysis of PM2.5 at multiple sites in Zhengzhou, China: implications for characterization and source apportionment at different pollution levels

Zhengzhou is one of the most heavily polluted cities in China. This study collected samples of PM_2.5 (atmospheric fine particulate matter with aerodynamic diameter ≤ 2.5 μm) at five sites in different functional areas of Zhengzhou in 2016 to investigate the chemical properties and sources of PM_2.5 at three pollution levels, i.e., PM_2.5 ≤ 75 μg/m³ (non-pollution, NP), 75 μg/m³ < PM_2.5 ≤ 150 μg/m³ (moderate pollution, MP), and PM_2.5 > 150 μg/m³ (heavy pollution, HP). Chemical analysis was conducted, and source categories and potential source region were identified for PM_2.5 at different pollution levels. The health risks of toxic elements were evaluated. Results showed that the average PM_2.5 concentration in Zhengzhou was 119 μg/m³, and the sum of the concentrations of SO₄^2-, NO₃^-, and NH₄⁺ increased with the aggravation of pollution level (23, 42, and 114 μg/m³ at NP, MP, and HP days, respectively). Positive Matrix Factorization analysis indicated that secondary aerosols, coal combustion, vehicle traffic, industrial processes, biomass burning, and dust were the main sources of PM_2.5 at three pollution levels, and accounted for 38.4%, 21.6%, 16.7%, 7.4%, 7.7%, and 8.1% on HP days, respectively. Trajectory clustering analysis showed that close-range transport was one of the dominant factors on HP days in Zhengzhou. The potential source areas were mainly located in Xinxiang, Kaifeng, Xuchang, and Pingdingshan. Significant risks existed in the non-carcinogenic risk of As (1.4-2.3) for children at three pollution levels and the non-carcinogenic risk of Pb (1.0-1.4) for children with NP and MP days.

Inhalable metal-rich air particles and histone H3K4 dimethylation and H3K9 acetylation in a cross-sectional study of steel workers

BACKGROUND

Epidemiology investigations have linked exposure to ambient and occupational air particulate matter (PM) with increased risk of lung cancer. PM contains carcinogenic and toxic metals, including arsenic and nickel, which have been shown in in vitro studies to induce histone modifications that activate gene expression by inducing open-chromatin states. Whether inhalation of metal components of PM induces histone modifications in human subjects is undetermined.

OBJECTIVES

We investigated whether the metal components of PM determined activating histone modifications in 63 steel workers with well-characterized exposure to metal-rich PM.

METHODS

We determined histone 3 lysine 4 dimethylation (H3K4me2) and histone 3 lysine 9 acetylation (H3K9ac) on histones from blood leukocytes. Exposure to inhalable metal components (aluminum, manganese, nickel, zinc, arsenic, lead, iron) and to total PM was estimated for each study subject.

RESULTS

Both H3K4me2 and H3K9ac increased in association with years of employment in the plant (p-trend = 0.04 and 0.006, respectively). H3K4me2 increased in association with air levels of nickel [β = 0.16; 95% confidence interval (CI), 0.03-0.3], arsenic (β = 0.16; 95% CI, 0.02-0.3), and iron (β = 0.14; 95% CI, 0.01-0.26). H3K9ac showed nonsignificant positive associations with air levels of nickel (β = 0.24; 95% CI, -0.02 to 0.51), arsenic (β = 0.21; 95% CI, -0.06 to 0.48), and iron (β = 0.22; 95% CI, -0.03 to 0.47). Cumulative exposures to nickel and arsenic, defined as the product of years of employment by metal air levels, were positively correlated with both H3K4me2 (nickel: β = 0.16; 95% CI, 0.01-0.3; arsenic: β = 0.16; 95% CI, 0.03-0.29) and H3K9ac (nickel: β = 0.27; 95% CI, 0.01-0.54; arsenic: β = 0.28; 95% CI, 0.04-0.51).

CONCLUSIONS

Our results indicate histone modifications as a novel epigenetic mechanism induced in human subjects by long-term exposure to inhalable nickel and arsenic.