How does the body detoxify itself naturally?

How are xenobiotics eliminated from the body? 

The main routes of elimination are urine, faeces and sweat. They play an important role in detoxifying the body by removing xenobiotics and waste products produced by the body. 

When a foreign chemical substance (xenobiotic) is introduced into the body, it enters the bloodstream.

Depending on its chemical properties, it will be stored in specific organs, transformed by the body and then eliminated. It is the bloodstream that will transport and diffuse the xenobiotic throughout the body. 

The blood is filtered by the kidneys to form urine, which is mainly composed of water. This will be stored temporarily in the bladder before being discharged.

However, the kidneys are not able to effectively eliminate some xenobiotics that are not very soluble in water and therefore in urine. These xenobiotics will spend a longer time in the blood.

In order to eliminate them, the body will have to carry out their biological transformation. This transformation is called metabolisation and the substances produced during this transformation are the metabolites. Metabolisation usually occurs in the liver and improves the solubility of xenobiotics in the urine. 

Hair and nails are manufactured by the body from elements in the bloodstream. Thus, they store endogenous and exogenous substances and also participate in the elimination of waste products from the body. 

Depending on their chemical nature, chemicals can be stored in part in tissues such as fat, brain, kidneys, bones or muscles.

With repeated or prolonged exposure, they accumulate in the body. This is the process of bioaccumulation. Once they have settled in the tissues, the xenobiotics can re-enter the bloodstream and be eliminated. However, the elimination process is longer and these substances are eliminated very slowly from the body. 

Stools mainly include substances that have not been absorbed by the body. 

Blood, urine and hair are therefore very interesting biological matrices for determining the exposome, as they include all the information on a person's exposure. 

How long do xenobiotics stay in the body? 

The time it takes for xenobiotics to enter the bloodstream depends on the route of exposure and the nature of the substance and can vary from a few minutes (inhalation) to a few hours (ingestion). 

Thus, even for a short period of time the body can be exposed to xenobiotics. 

The duration of the presence of xenobiotics in the body is variable and depends on many factors, in particular the physicochemical properties of the xenobiotics: solubility in water, lipophilic character (affinity for fatty tissue). 

Some heavy metals, such as lead, take several years to be eliminated from the body after exposure has stopped.