Nano-particle Study Generates More Heat Than Light

A new study published in the European Respiratory Journal is generating media attention, and some observers assert it may have far-reaching implications for the nano-tech industry. Is this warranted?

In this study, Song, et al., Exposure to nano-particles is related to pleural effusion, pulmonary fibrosis and granuloma, 34(3) Eur. Respir. J. 559-567 (2009), researchers at China's Capital University of Medical Sciences linked lung disease in seven Chinese workers, two of whom reportedly died, to nano-particle exposures in a print plant where a paste containing nano-particles was sprayed onto a polystyrene substrate, with subsequent heat-curing.

The study reported that seven young female workers (ages 18–47), exposed to nano-particles for 5–13 months, were admitted to the hospital, all with shortness of breath and pleural effusions. Polyacrylate, consisting of nano-particles, was confirmed in the workplace. Pathological examinations of the patients' lung tissue displayed non-specific pulmonary inflammation, pulmonary fibrosis, and foreign-body granulomas of pleura. By transmission electron microscopy, nano-particles were observed to have lodged in the cytoplasm and caryoplasm of pulmonary epithelial and mesothelial cells, but also were located in the chest fluid.

The authors expressed concern that long-term exposure to some nano-particles may be related to serious damage to human lungs.  But, putting the media reception aside, this study appears to do more to highlight the common sense need to follow good industrial hygiene practices than to provide compelling evidence of any unique health risks posed by engineered nano-particles. The plant sprayed a strong chemical paste and then heated plastic material in an enclosed space apparently lacking ventilation.  The room in which the women worked was small and unventilated for a significant part of their exposure period. Only on occasion, they wore mere "cotton gauze masks." 

From the study it appears that the workers had a complicated exposure history to a mix of chemicals; while there was a reported association of nano-particles with lung disease, it is unclear which, if any, of the chemical exposures might have contributed to the lung issues. Readers of MassTortDefense know that an association is not causation.  For example, formation of thermodegradation fume products are known to cause significant occupational disease, and paint spraying has been shown to be potentially harmful long before nano-sizing of chemicals was utilized. 

Moreover, sufficient exposure information necessary to even begin to think about a causal connection between exposure to nano-sized particles in the paste/dust and lung and heart disease in the workers was missing.  Clearly, there may be alternative explanations for what the study authors described finding in the patients.

As noted here before, NIOSH emphasizes the use of a variety of engineering control techniques, implementation of a risk management program in workplaces where exposure to nanomaterials exists, and use of good work practices to help to minimize worker exposures to nanomaterials.