Detecting nanoparticles in the open environment can be very difficult, both in gases and in liquids. Nanoparticles are so minuscule that they can only be detected by electron microscopes. Other Instruments that are capable of detecting and analyzing particles of a few nanometres were only developed recently. Exposure to airborne nanoparticles is low in terms of mass but could be significant in terms of numbers of particles. It is the number of particles, their size, and their surface characteristics can effect the way they behave in contact with organisms.

Inhalation is the main route of human exposure to nanoparticles, and motor vehicle emissions tend to constitute the most significant source of nanoparticles in urban areas. Exposure to airborne nanoparticles may also occur at some workplaces but data is scarce. Very little is known about the other routes of exposure, namely exposure through the skin and exposure through ingestion.

Nanoparticles can have the same dimensions as some biological molecules and can interact with these. In humans and in other living organisms, they may move inside the body, reach the blood and organs such as the liver or the heart, and may also cross cell membranes.

Insoluble nanoparticles are a greater health concern because they can persist in the body for long periods of time. The parameters of nanoparticles that are relevant for health effects are nanoparticle size (smaller particles can be more dangerous), chemical composition and surface characteristics, and shape.Inhaled nanoparticles can deposit in the lungs and then potentially move to other organs such as the brain, the liver, and the spleen, and possibly the foetus in pregnant women. Some materials could become toxic if they are inhaled in the form of nanoparticles. Inhaled nanoparticles may cause lung inflammation and heart problems.


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