Nanotoxicity in Humans

Routes for entry of nanotoxic nanoengineered nanoparticles into the Human body. Destinations of nanotoxic nanoengineered nanoparticles, after entering the Human body.

Preface

Following my article "The Roots of Nano-Fear Decoded", I start here an attempt to approach nanotoxicology and nanotoxicity. Later on, I will attempt to point out ways and propose solutions in order fight and prevent nanotoxicity.



Introduction

As I wrote in "Nanopollution Revised", addressing nanopollution without addressing nanotoxicology is (theoretically and practically) an artificial effort, I would say. Nanopollution is present in the environment, which in turn affects the biosphere (including Humans). The biosphere is exposed to the nanotoxicity and thereby contaminates the environment. There is therefore a circle inseparable. However, due to space limitations, this article will try to address the nanotoxicology and nanotoxicity.

Of course, what I write is in line with the way I understand this issue in the present.

Not all nanoparticles are nanotoxic. In my personal opinion, naturally occurring nanoparticles are not toxic. I can possibly consider some exceptions - if supported by scientific evidence (e.g. nanotoxic natural occurring nanoparticles released in forest fires). However, unfortunately not all forest fires are of natural origin. Nature has already demonstrated many times that knows how to ensure balance and harmony rather than the Mankind knows how. The Mankind must increasingly learn the lessons that nature has to teach us all.

Furthermore, even though some exceptions as valid, it does not seem to me that the nanotoxicity of naturally occurring nanoparticles has meaning when compared with the nanotoxicity (under study) on some nanoengineered nanoparticles.

Moreover, I believe that not all nanoengineered nanoparticles are toxic. In other words, I believe that:

• Only a part of them are nanotoxic;
• Some are harmless to the health;
• And others are beneficial to the health.

Of course that my personal opinion has to be demonstrated scientifically, based on evidences.

Nanotoxicity obviously affects all living beings (including of course Humans). I will focus this article on some aspects of nanotoxicity in Humans, caused by the nanoengineered nanoparticles which are nanotoxic.


Routes For Entry of Nanotoxic Nanoengineered Nanoparticles Into The Human Body

Generally, nanotoxic nanoengineered nanoparticles can enter into the Human body through incidental and/or involuntary episodes. These incidental and/or involuntary episodes may be associated with a lack of knowledge by Humans. Therefore, through episodes of incidental and involuntary nature, the nanoparticles can enter the human body via (not necessarily in that order):

• Inhalation;
• Cutaneous;
• Ingestion;
• Other.

As an example, Humans can:

• Inhale incidentally and/or involuntarily air contaminated with nanotoxic nanoengineered nanoparticles;
• Incorporate into their bodies incidentally and/or involuntarily, through their skin (via cutaneous respiration) air contaminated with nanotoxic nanoengineered nanoparticles;
• Eat incidentally and/or involuntarily food contaminated with nanotoxic nanoengineered nanoparticles; 
• Drink incidentally and/or involuntarily water and consumer drinks contaminated with nanotoxic nanoengineered nanoparticles.

Destinations of Nanotoxic Nanoengineered Nanoparticles, After Entering The Human Body

After entering the Human body, nanotoxic nanoengineered nanoparticles can undergo different fates:

1. Can be totally or partially excreted;
2. Can be totally or partially metabolized;
3. Can be totally or partially cumulated into cells, tissues and organs.

Nanotoxic nanoengineered nanoparticles can be excreted, for example:

• Through the kidneys, during the blood filtration in which the nanotoxic nanoengineered nanoparticles are to be a product of excretion (a constituent of the urine);
• Through the intestines, during the formation of faeces and excreted through the anus;
• Through the sweat glands in order to be excreted in sweat during perspiration;
• Through the lungs (after venous blood having executed gas exchanges with the lung alveoli) being released into the environment during the exhalation.

Nanotoxic nanoengineered nanoparticles can be metabolized: 

• In the liver; 
• In the spleen.

Nanotoxic nanoengineered nanoparticles can circulate in the blood stream and lymphatic vessels. Through this path, they can travel around the entire Human body and eventually accumulate into diverse organs (e.g. brain cells).

Insoluble or low solubility nanotoxic nanoengineered nanoparticles in biological fluids are a great cause for concern.

Some insoluble or low solubility nanotoxic nanoengineered nanoparticles can pass through the several defence mechanisms of the Human body. Thus, these insoluble or low solubility nanotoxic nanoengineered nanoparticles can then be transported through the body in insoluble form. Therefore, some insoluble or low solubility nanotoxic nanoengineered nanoparticles can pass to the bloodstream (blood vessels and/or lymphatic vessels) after passing through the respiratory membranes (pulmonary alveoli, through gas exchanges) and/or gastrointestinal membranes. These insoluble or low solubility nanotoxic nanoengineered nanoparticles are then distributed to various organs and eventually can accumulate at specific locations. 

Other insoluble or low solubility nanotoxic nanoengineered nanoparticles find a direct shortcut to the brain: after inhalation, travel along the olfactory nerves and penetrate directly into the brain neurons.


Final Comment

Given my personal belief that nanotoxicity of nanoparticles is practically caused only by nanotoxic nanoengineered nanoparticles, nanotoxicology and nanotoxicity are relatively new subjects that emerged after the appearance of nanofabrication.