TOXICOLOGY: The Science of Poisons

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“The Science of Poisons” defines what toxicology is but the more appropriate definition is that toxicology is the study of the adverse effects of chemicals on living organisms. It is the study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people.

These adverse effects may occur in many forms, ranging from immediate death to subtle changes not realized until months or years later. They may occur at various levels within the body, such as an organ, a type of cell, or a specific biochemical. Knowledge of how toxic agents damage the body has progressed along with medical knowledge. It is now known that various observable changes in anatomy or body functions actually result from previously unrecognized changes in specific biochemicals in the body.

A photo showing different drugs.
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Toxicity is complex with many influencing factors; dosage is the most important. Xenobiotics cause many types of toxicity by a variety of mechanisms. Some chemicals are themselves toxic. Others must be metabolized (chemically changed within the body) before they cause toxicity.

Xenobiotic is a term used to describe foreign substances taken into the body. The word is taken from the Greek xeno, meaning "foreigner". Xenobiotics do not just produce toxic effects, but can also produce beneficial ones as in the case of pharmaceuticals. Whereas high doses of certain toxins in the body can lead to death, smaller doses may be harmless or even beneficial. This is known as the dose-response relationship, a major concept in toxicology.

Toxicity can result from adverse cellular, biochemical, or macromolecular changes like for example:

• cell  replacement (fibrosis)
• damage to an enzyme system
• disruption of protein synthesis
• production of reactive chemicals in cells

Factors that can affect toxicity of a substance:

• form and innate chemical activity
• dosage
• exposure route 
• species
• age
• sex
• ability to observed 
• metabolism 
• excretion 
• distribution within the body 
• presence of other chemicals 

BRANCHES OF TOXICOLOGY

• Risk assessment is a branch of toxicology which attempts to determine, probabilistically, outside the laboratory, the likelihood of an adverse effect based on a particular exposure scenario. This is not experimental activity, involves much more uncertainty about its findings and is as much art as science. It is conducted quantitatively, relying on mathematics and computer modeling, or qualitatively, relying more on experience and similar scenarios that have been previously looked at.

• Regulatory toxicology relies on risk assessment and experimental data to determine the risk and benefits, or the costs and benefits of exposure to certain chemicals, to determine whether such chemical will be allowed in the public sphere and to what extent its use and exposure will be regulated. This field of toxicology probably has the greatest effect on our daily lives of all the different fields of toxicology.

• Clinical toxicology involves the application of toxicological principles within a diagnostic setting, usually to determine whether a presenting adverse effect or disease or injury is due to some type of chemical exposure. This area of toxicology is typically practiced by a physician, nurse or other clinician, often times in consultation with the experimental toxicologist, who is in a position to better explain certain published experimental findings and whether they would be applicable to the case at hand.

• Forensic toxicology focuses on medical-legal aspects  of chemical exposure and toxic injury. Evaluation of analytical chemistry techniques and measurements, and testimony of conclusions and opinions in courts of law encompass the activity of this specialized field of toxicology.

• Environmental Toxicology is also known as entox, is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms.

For better understanding of Toxicology, here are some of the terminologies to be known:

• Toxic agent is anything that can produce an adverse biological effect. It may be chemical, physical, or biological in form. 
• Toxic substance is simply a material which has toxic properties. It may be a discrete toxic chemical or a mixture of toxic chemicals. 
• Systemic toxin is one that affects the entire body or many organs rather than a specific site. 
• Benzene is a specific organ toxin in that it is primarily toxic to the blood-forming tissues.
• Lead is also a specific organ toxin; however, it has three target organs (central nervous system, kidney, and hematopoietic system).
• Germ cells are those cells that are involved in the reproductive process and can give rise to a new organism. They have only a single set of chromosomes peculiar to a specific sex.
• Somatic cells are all body cells except the reproductive germ cells. They have two sets (or pairs) of chromosomes.

REFERENCES:
http://www.themoldsource.com/experts/Toxicology.html
http://www.wisegeek.com/what-is-toxicology.htm
http://www.toxicologysource.com/whatistoxicology.html