Cigarette-related cadmium and environmental pollution exposure are reflected in airway ultrafine particle content

Biomarkers of the relationship of particulate matter exposure with the progression of chronic respiratory diseases

A high level of particulate matter (PM) in air is correlated with the onset and development of chronic respiratory diseases. We conducted a systematic literature review, searching the MEDLINE, EMBASE, and Cochrane databases for studies of biomarkers of the effect of PM exposure on chronic respiratory diseases and the progression thereof. Thirty-eight articles on biomarkers of the progression of chronic respiratory diseases after exposure to PM were identified, four of which were eligible for review. Serum, sputum, urine, and exhaled breath condensate biomarkers of the effect of PM exposure on chronic obstructive pulmonary disease (COPD) and asthma had a variety of underlying mechanisms. We summarized the functions of biomarkers linked to COPD and asthma and their biological plausibility. We identified few biomarkers of PM exposure-related progression of chronic respiratory diseases. The included studies were restricted to those on biomarkers of the relationship of PM exposure with the progression of chronic respiratory diseases. The predictive power of biomarkers of the effect of PM exposure on chronic respiratory diseases varies according to the functions of the biomarkers.

COVID-19 Lockdown in Israel: The Environmental Effect on Ultrafine Particle Content in the Airway

Inhaled ultrafine particle (UFP) content in exhaled breath condensate (EBC) was observed as an airway inflammatory marker and an indicator of exposure to particulate matter (PM). The exceptional decline in air pollution during the COVID-19 lockdown was an opportunity to evaluate the effect of environmental changes on UFP airway content. We collected EBC samples from 30 healthy subjects during the first lockdown due to COVID-19 in Israel (March–April 2020) and compared them to EBC samples retrieved during April–June 2016 from 25 other healthy subjects (controls) living in the same northern Israeli district. All participants underwent EBC collection and blood sampling. Ambient air pollutant levels were collected from the Israeli Ministry of Environmental Protection’s online database. Data were acquired from the monitoring station closest to each subject’s home address, and means were calculated for a duration of 1 month preceding EBC collection. UFP contents were measured in the EBC and blood samples by means of the NanoSight LM20 system. There was a dramatic reduction in NO, NO₂, SO₂, and O₃ levels during lockdown compared to a similar period in 2016 (by 61%, 26%, 50%, and 45%, respectively). The specific NO₂ levels were 8.3 ppb for the lockdown group and 11.2 ppb for the controls (p = 0.01). The lockdown group had higher UFP concentrations in EBC and lower UFP concentrations in serum compared to controls (0.58 × 10⁸/mL and 4.3 × 10⁸/mL vs. 0.43 × 10⁸/mL and 6.7 × 10⁸/mL, p = 0.05 and p = 0.03, respectively). In this observational study, reduced levels of air pollution during the COVID-19 lockdown were reflected in increased levels of UFP airway contents. The suggested mechanism is that low airway inflammation levels during lockdown resulted in a decreased UFP translocation to serum. Further studies are needed to confirm this hypothesis.

Trajectory of inhaled cadmium ultrafine particles in smokers

Introduction

Tobacco smoking is a significant source of cadmium exposure among smokers. Most of inhaled heavy metals, including cadmium, are attached to ultrafine particles (UFPs) surface. A low inhaled UFP content in exhaled breath condensate reflects a high inflammatory status of airways. Increased respiratory epithelial permeability and translocation to the circulation is the proposed mechanism. UFP recovered from smokers’ airways have high levels of cadmium compared with the airways of non-smokers.

Methods

Urine was collected from 22 smokers subjects and 43 non-smokers. Samples were analysed for UFP and cadmium content. UFP were measured in urine samples by means of the NanoSight LM20 system (NanoSight, UK). A Niton XL3 X-ray fluorescence spectrometer analyzer (Thermo Fischer Scientific, Germany) quantified heavy metal contents in the urine samples.

Results

Smokers had elevated UFP and cadmium content in urine compared with non-smokers (4.6 E8/mL and 20.6 ppm vs 3.4 E8/mL and 18.5 ppm, p=0.05 and p=0.05, respectively). Smokers had elevated levels of lead and rubidium compared with non-smokers (8.9 ppm and 27 ppm vs 7.8 ppm and 2 ppm, p=0.05 and p=0.04, respectively)

Discussion

We suggest that the trajectory of cadmium-related UFP in smokers begins by its inhalation into the airways. The UFPs induce inflammation and oxidative stress in the small airways, are subsequently translocated from the interstitium to the circulation and are finally detected and secreted in urine