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

Particulate matter (PM) and cigarette-related cadmium exposure increases inflammation and smokers' susceptibility to developing lung diseases. The majority of inhaled metals are attached to the surface of ultrafine particles (UFPs). A low inhaled UFP content in exhaled breath condensate (EBC) reflects a high inflammatory status of airways.

EBC was collected from 58 COPD patients and 40 healthy smokers and nonsmokers. Participants underwent spirometry, diffusion capacity, EBC and blood sampling. Environmental pollution data were collected from monitoring stations. UFPs were measured in EBC and serum, and cadmium content was quantified.

Subjects with low UFP concentrations in EBC (<0.18×10⁸·mL^-1) had been exposed to higher long-term PM_2.5 levels versus subjects with high UFP concentrations in EBC (>0.18×10⁸·mL^-1) (21.9 µg·m^-3 versus 17.4 µg·m^-3, p≤0.001). Long-term PM_2.5 exposure levels correlated negatively with UFP concentrations in EBC and positively with UFP concentrations in serum (r=-0.54, p≤0.001 and r=0.23, p=0.04, respectively). Healthy smokers had higher cadmium levels in EBC versus healthy nonsmokers and COPD patients (25.2 ppm versus 23.7 ppm and 23.3 ppm, p=0.02 and p=0.002, respectively). Subjects with low UFP concentrations in EBC also had low cadmium levels in EBC versus subjects with high UFP levels (22.8 ppm versus 24.2 ppm, p=0.004).

Low UFP concentration in EBC is an indicator of high-level PM exposure. High cadmium levels in EBC among smokers and the association between cadmium and UFP content in EBC among COPD patients indicate cadmium lung toxicity.