Evidence from environmental health research could eventually lead to liability exposure, based on material contribution. Of more immediate concern is the support for setting an occupational exposure standard; which would include nanoparticles.
Evidence from:
Committee on the Medical Effects of Air Pollutants (COMEAP) (2010) ISBN 978-0-85951-685-3
The Mortality Effects of Long-Term Exposure to Particulate Air Pollution in the United Kingdom
PM2.5 exposure is diffuse in nature and as such a specific insured would be hard to identify. Even if they were identified, the likelihood is that the pollution is not sudden and accidental. However, given the developing theory of liability for diffuse effects (climate change, biodiversity) it is conceivable that liability for PM2.5 exposure could one day be an issue for heart disease and stroke.