Nanotechnologies are producing impressive results in an ever increasing number of sectors and their market could reach a value of 200 billion euros in 2010. However, the nanoparticles on which they are based pose a serious risk to the lungs, even more so than the notorious ultrafine particles present in air pollution. This is the groundbreaking message of the Chinese study published in the forthcoming issue of the European Respiratory Journal (ERJ), the scientific peer-reviewed publication of the European Respiratory Society. Not only did exposure to nanoparticles in adhesive paint cause severe pulmonary fibrosis in a group of young female workers; two of them developed fatal lung failure. Given the increasing enthusiasm for nanotechnologies, the authors urge that priority be given to protecting the public and the workforce.

Nanotechnology is no longer confined to science fiction. In recent years, the technology of tiny particles has invaded every aspect of our daily lives. Tennis racquets, special-purpose fabrics, fuels, household articles, even paints: many everyday products now have components measurable on the scale of a nanometre, or one billionth of a metre. Nanotechnologies are also popular in the cosmetics industry, particularly in sunscreens, and the pharmaceuticals industry is likewise conducting very active research into the production of 'smart' drugs that perform even better.

While nanoparticles' diminutive size means they have unprecedented physical properties (such as diffusion, resistance or flexibility of use) that are invaluable in industrial applications, it also raises the question of their toxicity for consumers and the workforce. Their tiny diameter means that they can penetrate the body's natural barriers, particularly through contact with damaged skin or by inhalation or ingestion.

Moreover, their toxicity has already been established in animals: mice were found to develop symptoms of inflammation and pulmonary fibrosis following application of carbon nanoparticles to the trachea. But until now no cases had been reported in humans. The revelations to be published in the ERJ by a Beijing team will thus break new ground and relaunch the debate on the dangers of nanotechnologies.

Risk to heart and lungs

The study, by a team led by Yuguo Song, of the Occupational Disease and Clinical Toxicology Department at Chaoyang Hospital in Beijing, involved seven healthy young women employed in a print plant. Over the course of a few months, all of the women were hospitalised for respiratory problems, accompanied by itchy eruptions of the skin on the face and arms.

On examination, the patients were found to have liquid effusion around the heart and lungs, which proved resistant to all treatments. Comprehensive investigation led to a diagnosis, in all cases, of pulmonary fibrosis with consequent impairment of lung function.

The Chinese team's suspicions were raised in particular by the results from electron microscopy of the chemical used, lung biopsy tissue and pleural effusion liquid. All three were found to contain round nanoparticles with a diameter of approximately 30 nanometres, which could even be found in the cytoplasm of the pulmonary epithelial and mesothelial cells.

According to Yuguo Song, these particles must originate in the polyacrylate-based adhesive paints used by the women daily in the course of their work. He emphasises that, despite repeated efforts, he has not at this stage been able to obtain precise data on the composition of the paint in question. Likewise, the researchers have not been able to determine the workers' level of exposure through measurement of airborne particles, since the workshop was closed down several months before their investigation began.

But that was not the end of the matter. Researchers at Beijing Chaoyang Hospital, together with the Chinese Centre for Disease Control, were able through careful detective-style investigation of the women's working conditions and analysis of lung biopsy tissue and pleural effusion liquid to reconstruct the probable sequence of events that led to their poisoning with nanoparticles.

Unventilated premises

Before their respiratory symptoms led them to consult a doctor, the seven young women had been working for between 5 and 13 months in the same workshop, where white paint was sprayed onto polystyrene slabs. The spraying, and the heating and drying of the polystyrene slabs, were part of an automatic process; the workers' task was, using a large scoop, to load the machine with adhesive paint, made up of polyacrylic esters, and handle the slabs.

The researchers learned that, in the months leading up to the workers' illness, the 70 m2 workshop had been very poorly ventilated. It was windowless, the door remained closed because of the cold, and the ventilation system had broken down five months earlier. "The workers, of peasant origin, were also completely unaware of workplace health and safety regulations and of the potential toxicity of the materials they were handling", explains Yuguo Song. "Their only protection, used sporadically, was cotton gauze masks." When interviewed, the women mentioned that flecks were often present in the air and this seemed to cause itching on their face and arms.

A new challenge

Despite these unfavourable conditions, the authors of the ERJ article maintain that this was not simply a case of intoxication by paint vapour as a result of poor ventilation, but that the illness was caused by the inherent toxicity of the nanoparticles, which entered the body either through the airways or through the skin, or perhaps through both. "It is clear that the symptoms, the examination results and the progress of the disease in our patients differ markedly from respiratory pathologies induced by paint inhalation", Yuguo Song emphasises. By way of evidence, he points to the fact that, within two years, two of the women died and the other patients' pulmonary fibrosis continued slowly to develop even once the exposure had stopped.

No further cases were identified, since the machine was shut down after the workers became ill.
Many questions remain unanswered, the Chinese researchers admit, including the precise nature of the particles involved.
They insist, however, that the risks of nanoparticles must be assessed urgently and effective protection systems developed. "We call on scientists throughout the world to work together and address this new challenge", Yuguo Song concludes in the ERJ.

Title of the original article:
"Exposure to nanoparticles is related to pleural effusion, pulmonary fibrosis and granuloma"

Source
European Respiratory Journal