Caution: It's Toxic!!!

INTRODUCTION

Photo credit to: http://sciencegames.4you4free.com/poisons_toxicologist.gif

“All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.”

 – Paracelsus (1493-1541)

The quotation above illustrates that all chemicals could be toxic but the degree of the effect depends on the dose or degree of exposure.

            Toxicology is defined as the scientific study of toxins or poisons, which may cause adverse effects when administered by a living organism.  An adverse effect is the abnormal or harmful effect following exposure to the toxic substance. The effect can be a severe injury or death. On the other hand, these substances can also be used safely. In other words, the risk from these substances depends on the dose and exposure. (And this explains the above quotation).

AREAS OF TOXICOLOGY

The field of toxicology can be divided into following disciplines:

Mechanistic toxicology – it focuses on understanding specific chemical, biochemical and molecular mechanisms by which toxicants have their effects.

Descriptive toxicology – it focuses on the testing of chemicals and it provides information for safety evaluation and regulatory requirements.

Regulatory toxicology – deals with the risk decision-making based on data from mechanistic and descriptive toxicology. It sets standards for “safe” exposure.

Forensic toxicology – deals with the medical and legal aspects of toxicants on humans and animals.

Clinical toxicology – 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.

Occupational toxicology – concerned with health effects from exposure to chemicals in the workplace.

Environmental toxicology – deals with the study of the effects of chemicals in the body.

ROUTES OF EXPOSURE

Photo credit to: http://www.docstoc.com/docs/568884/General-diagram-of-routes-of-exposure-and-Module-Two-Routes-of-Exposure

Toxicity may depend on the route of exposure at which the substance is absorbed.

·            Dermal (Skin contact) – it is the common route of exposure. Skin acts as a barrier against entry of most chemicals thus reduces the toxic exposure.

·        Inhalation – it is said to be the most dangerous route of entry because it readily allows passage of chemicals to the lungs.

·    Ingestion – chemicals that are ingested may be absorbed into circulation along the gastrointestinal tract.

TYPES OF TOXIC EFFECTS ACCORDING TO EXPOSURE

ACUTE TOXICITY	CHRONIC TOXICITY
Exposure to a single large dose Associated with short-term exposure to  a substance Effects: often reversible Example: Carbon monoxide or cyanide poisoning	Exposure to multiple doses Associated with prolonged/repeated exposure to a substance Effects: often irreversible Example: lead or mercury poisoning

PHYSIOLOGICAL CLASSIFICATION OF TOXIC RESPONSES

Class	Effect
Irritant	Causes inflammation of the skin and mucous membranes (skin, eyes, nose, or respiratory system).
Corrosive	A material that can destroy human tissue. Includes both acids and bases and may be a solid liquid or gas. Most common toxic material encountered in the laboratory.
Asphyxiant	A material that deprives tissue of oxygen and causes suffocation by displacing oxygen or interfering chemically with oxygen absorption, transport or utilization.
Anesthetic	Depresses the central nervous system Example: alcohols, halogenated hydrocarbons
Hepatotoxin	Causes liver damage. Example: carbon tetrachloride
Nephrotoxin	Causes kidney damage. Example: chloroform, mercury, dimethyl sulfate
Neurotoxin	Affects the nervous system. Example: mercury, lead, carbon disulfide
Hematopoietic toxin	affects the cellular components of blood or its ability to function Example: benzene, xylene, CO, cyanides
Pulmonary toxin	Irritates or damages the lungs. Example: asbestos, silica ozone. chromium
Reproductive toxins	Causes impotence or sterility in men and women. Example: lead, dibromodichloropropane
Carcinogen	A material which can cause cancer. Example: asbestos, Bis-chloromethyl ether, benzene, acrylonitrile
Mutagen	Anything which causes a change in the genetic material of a living cell. Many mutagens are also carcinogens.
Teratogen	A material which interferes with the developing embryo when a pregnant female is exposed to that substance. Example: lead, thalidomide

Table from: http://learn.caim.yale.edu/chemsafe/references/classification.html

The importance of studying toxicology is that, understanding toxicology could reduce the possibility of human exposure to the harmful effects of toxicants. So I hope that somehow, you’ve learned something from this article and share it to others.

Thank you for reading, and watch out for my next article. :)

God Bless!!!

“Let the wise hear and increase in learning, and the one who understands obtain guidance”  - Proverbs 1:5

 References:

Duffus, John H. and Worth, Howarth G.J. Fundamental Toxicology

Hodgson, Ernest. A Textbook of Modern Toxicology 4^th Edition

Bishop, M., Fody, E., and Schoeff, L., Clinical Chemistry: Techniques, Principles, Correlations, 6th Edition

http://www.merckmanuals.com/vet/toxicology/toxicology_introduction/absorption_distribution_metabolism_and_excretion.html

http://www.agius.com/hew/resource/toxicol.htm

http://safety.science.tamu.edu/toxics.html

http://www.toxicologyguide.com/871-Environmental-Toxicology/

http://learn.caim.yale.edu/chemsafe/references/classification.html