**Conflict of interest**

None.

### **Declarations and acknowledgements**

The writing of this chapter is supported by the National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health with also feedback on microscopy methods by Richard Leapman and colleagues (Maria Aronova), and the Department of Environmental Medicine and Public Health, Mount Sinai School of Medicine, USA with feedback in the system by John Meyer on respiratory particulates, and James Godbold in Biostatistics on post-analyses of Ref. 31 study data. Additional feedback was provided by Behzad Ghanbarian on solution percolation, Mark Goldberg and Jack Caravanos on the air sampling and industrial hygiene, Phil Landrigan on the initial Lead smelter study and exposure thresholds, Roberto Lucchini on the effects of Manganese exposure-related toxicity to susceptible populations, Paul Tofts on the vascular plasma term modification in the general kinetic model, Charles Michel on the convective effects of macromolecules, and Gunter Oberdorster on the inhalation toxicology aspects. All previous co-authors including John Butman, Steve Fung, Ariel Kanevsky, Colin Wilson, Haitao Wu, Alioscka Sousa and Matthew Hall have reviewed the pertinent contents.
