Effects of nanoparticles on lung damage in humans

To the Editors:

We read with great interest a recent article in the European Respiratory Journal by Song et al. 1 and we would like to add some questions/comments to their paper. First, we are interested in the (estimated) total weight of the polyacrylate nanoparticles detected in the lungs and/or pleural fluids obtained from the patients. In our in vivo experiments, mice were exposed seven times per week to nanoparticles (carbon black 2 and latex 3) at the weight of 50 μg·time⁻¹·animal⁻¹ (∼83 mg in the human body), and did not die within 6 months thereafter (unpublished observation). Taken together, results from the study in humans by Song et al. 1 and our in vivo studies may provide an important finding regarding difference in susceptibility to nanoparticles between humans and rodents. The second point to be addressed is the possibility of endotoxin attaching to (around) the nanoparticles. Do the authors have any information about endotoxin level in the lung samples or endotoxin concentration in the workplace? We have previously demonstrated that combined exposure to nanoparticles and endotoxin elicited devastating lung injury compared to nanoparticles or endotoxin alone 4. The lethal events occurring in the patients may have resulted from synergistic effects of nanoparticles with other toxic substances, rather than effects of the nanoparticles alone. Finally, we would like to know if these seven patients had pre-existing atopy. In particular, we are interested in the physical condition of the patients described in “The general characteristics of the patients” section in which “all patients suffered from rash with intense itching on their faces” 1, implicating an association with some immunological impairment. Allergen-specific immunoglobulin (Ig)E titres examined by radioallergosorbent test could provide hints for detection, as total IgE (measured by radioimmunosorbent test) does not always cover allergic conditions. Furthermore, atopic subjects are prone to particulate matter (PM), i.e. PM exposure significantly exacerbates the pathophysiology in the subjects 2, 5, sometimes leading to a fatal outcome. A careful search for pre-existing illness (in particular, atopy) may have helped in resolving the pathogenesis of the lung damage seen in the patients. In any case, the study by Song et al. 1 is valuable for future inhalation toxicology, and environmental and preventive medicine, if correlated to previous in vivo findings.

Statement of interest

None declared.