What's behind the word "TOXIC"?

1 Rescue me, LORD, from evildoers;

   protect me from the violent,

2 who devise evil plans in their hearts

   and stir up war every day.

3 They make their tongues as sharp as a serpent’s;

   the poison of vipers is on their lips

-Psalms 140:1-3 (NIV)

Photo Credit: http://www.momeomagazine.com/tag/training-people-how-to-treat-you/ 

You might wonder why I started my blog with verses from the Bible. (again, this is not a Bible study Guys :)) A poisonous or toxic thing for me, is not simply a substance that may harm  someone or something but a tuckless or negligible word being held-out by a person that has negative impact on others.(perhaps, a TOXIC FRIEND. Haha) Death and life are in the power of the tongue so we should be careful in using this muscular hydrostat on the floors of the mouths. :)

The word "Toxic" as defined in Merriam-Webster dictionary, is containing or being a poisonous material especially when capable of causing death or serious debilitation but for us Medical students, specifically Medical Technology Students here in Angeles University Foundation, being toxic means, being in a state of stress and exhaustion. Why am I saying this by the way? Most of us, are familiar with this word, but does not have a better understanding of it. As we go on, you will learn more about it.

Peter Mere Latham (1789-1875) is credited with the statement "Poisons and Medicines are oftentimes the same substance given with different intents". While this remark was penned in a bygone error, it is probably truer today that it was then. Sometimes, the thing that is intended to benefit us, may harm us when we improperly used or utilized it. 

What is Toxicology? 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. It may also be defined as a science that combines biology and chemistry to study poisons and their effect on biological systems. Toxicology addresses a variety of questions. For example, in agriculture, toxicology determines the possible health effects from exposure to pesticides or herbicides, or the effect of animal feed additives, such as growth factors, on people. Toxicology is also used in laboratory experiments on animals to  establish dose-response relationships. Toxicology also deals with the way chemicals and waste products affect the health of an individual.

Photo Credit:  http://www.gaia-health.com/articles101/000142-by-law-chemicals-dont-have-to-be-listed-if-hurts-profits.shtml

Sub-Disciplines of Toxicology	Description
Environmental Toxicology	Concerned with the study of chemicals that contaminate food, water, soil, or the atmosphere. It also deals with  toxic substances that enter bodies of waters such as lakes, streams, rivers, and oceans
Occupational (Industrial) Toxicology	Concerned with health effects from exposure to chemicals in the workplace. This field grew out of a need to protect workers from toxic substances and to make their work  environment safe
Regulatory Toxicology	Gathers and evaluates existing toxicological information to establish concentration-based standards of “safe” exposure. The standard is the level of a chemical that a person can be exposed to without any harmful health effects
Food Toxicology	involved in delivering a safe and edible supply of food to the consumer
Clinical Toxicology	Concerned with diseases and illnesses associated with short term or long term exposure to toxic chemicals
Descriptive Toxicology	Concerned with gathering toxicological Information from animal experimentation. These types of experiments are used to establish how much of a chemical would cause illness or death.
Forensic Toxicology	Used to help establish cause and effect relationships between exposure to a drug or chemical and the toxic or lethal effects that result from that exposure.
Analytical toxicology	Identifies the toxicant through analysis of body fluids (e.g. urine, blood, bile, oral fluid, vitreous humor or cerebrospinal fluid) and tissues (brain cortex, liver, heart, kidney, fat tissues), stomach content, and/or drug paraphernalia. Hair is mostly used to detect long-term exposure to drugs of abuse.
Mechanistic Toxicology	Makes observations on how toxic substances cause their effects. The effects of exposure can depend on a number of factors, including the size of the molecule, the specific tissue type or cellular components affected, whether the substance is easily dissolved in water or fatty tissues.

Photo Credit:  http://www.chicagonow.com/so-you-have-a-girlfriend/2012/03/the-toxic-relationship-2/ 

Classification of Toxic Agents:

Toxic substances are classified into the following:

A.  Heavy Metals

Metals differ from other toxic substances in that they are neither created nor destroyed by humans. Their use by humans plays an important role in determining their potential for health effects. Their effect on health could occur through at least two mechanisms: first, by increasing the presence of heavy metals in air, water, soil, and food, and second, by changing the structure of the chemical. For example, chromium III can be converted to or from chromium VI, the more toxic form of the metal.

B.  Solvents and Vapors

Nearly everyone is exposed to solvents. Occupational exposures can range from the use of “white-out” by administrative personnel, to the use of chemicals by technicians in a nail salon. When a solvent evaporates, the vapors may also pose a threat to the exposed population.

C.  Radiation and Radioactive Materials

Radiation is the release and propagation of energy in space or through a material medium in the form of waves, the transfer of heat or light by waves of energy, or the stream of particles from a nuclear reactor.

D.Dioxin/FuransDioxin, (or TCDD) 

It was originally discovered as a contaminant in the herbicide Agent Orange. Dioxin is also a by-product of chlorine processing in paper producing industries.

E.  Pesticides

The EPA defines pesticide as any substance or mixture of substances intended to prevent, destroy, repel, or mitigate any pest. Pesticides may also be described as any physical, chemical, or biological agent that will kill an undesirable plant or animal pest.

F. Microbial toxins

Bacteria, fungi and algae are the microorganisms typically associated with  microbial toxin production. Cholera toxin produced by Vibrio cholerae is the virulence factor responsible for the massive secretory diarrhea seen in Asiatic cholera (5 million cases each year).

G. Mushroom toxins

Several mushroom species (e.g. Amanita phalloides, A. virosa), produce a family of cyclic octapeptides called amanitins. Symptoms of intoxication appear at the end of a latent period of 6-48 hours during which the patient shows no symptoms.

H.  Plant Toxins

Different portions of a plant may contain different concentrations of chemicals. Some chemicals made by plants can be lethal. For example, taxol, used in chemotherapy to kill cancer cells, is produced by a species of the yew plant.

I.  Animal Toxins

These toxins can result from venomous or poisonous animal releases.

Subcategories of Toxic Substance Classifications

All of these substances may also be further classified according to their:

•  Effect on target organs (liver, kidney, hematopoietic system),
•  Use (pesticide, solvent, food additive),
•  Source of the agent (animal and plant toxins),
•  Effects (cancer mutation, liver injury),
•  Physical state (gas, dust, liquid),
• Labeling requirements (explosive, flammable, oxidizer),
• Chemistry (aromatic amine, halogenated hydrocarbon), or
• Poisoning potential (extremely toxic, very toxic, slightly toxic)

References:

 Poisoning and Toxicology Compendium with Symptoms Index by Jerrold B. Leikin (1998) Clinical Chemistry: Techniques, Principles, Correlations 6th Ed. by Michael L. Bishop et al. (2010)

http://www.eoearth.org/article/History_of_toxicology

http://www.thebts.org/Careers/ToxicologyDisciplines.aspx

http://www.lnt.ch/Toxicology.pdf