Introduction
Do the characteristics of MNPs differ from those of other ANPs?
Characteristics | ANPs | MNPs |
---|---|---|
Source | Combustion | Engineering (controlled synthesis) |
Most popular class | Volatile organics, sulpur compounds and carbonaceous agglomerates | Silver, TiO2 and CNTs |
Physicochemical properties | Volatile or semi-volatile, scattering and absorption | Non–volatile, conductive, super–hard, optical absorption, magnetism (properties of MNPs differ from those of their bulk material) |
Organic chemical content | High | Low |
Metal impurities | Low | Varies |
Atmospheric release | Intentional or incidental (fugitive) | Unintentional or incidental (fugitive) (during production, handling, use and disposal of MNP products) |
Atmospheric life time | Low | Unknown (expected to be relatively larger than ANPs but depending on type) |
Preferred measurement metric for regulation | Number | Unknown (number, mass or surface area) |
General shape of particle number/size distributions | Bi–modal (changing continuously due to the effect of transformation processes) | Unimodal or bimodal depending on material |
Exposure route | Oral, dermal, inhalation | Oral, dermal, inhalation or ingestion |
Adverse health effects | Fairly well known | Largely unknown |
Surface area/volume | High | High |
Uniformity in shape, size and functionality | Low | High |
Instruments generally used for measuring ambient number distributions | SMPS, DMS500, DMS50, ELPI, CPC, CNC, APS, FMPS, UFP, LAS | SMPS, CPC |