CHAPTER 8 : TOXICOLOGY

Toxicology 
-(from the Ancient Greek words τοξικός toxikos "poisonous" and λόγος logos) is a branch of biology, chemistry, and medicine (more specifically pharmacology) concerned with the study of the adverse effects of chemicals on living organisms.^[1] It also studies the harmful effects of chemical, biological and physical agents in biological systems that establishes the extent of damage in living organisms. The relationship between dose and its effects on the exposed organism is of high significance in toxicology. Factors that influence chemical toxicity include the dosage (and whether it is acute or chronic); the route of exposure, the species, age, sex and environment.
- Environmental toxicology is defined as the study of the fate and effects of chemicals in the environment.
-Although this definition would encompass toxic chemicals naturally found in the environment (i.e., animal venom, microbial and plant toxins), environmental toxicology is typically associated with the study of environmental chemicals of anthropogenic origin.
-Environmental toxicology can be divided into two subcategories: environmental health toxicology and ecotoxicology. 

(www.toxicologyguide.com)

Types of Toxicants

As mentioned before, there's a wide variety of toxicants in the environment. To better understand them, we can put them into specific categories that are based on the types of problems they cause.  
Carcinogens are probably the best-known toxicant because these are cancer-causing chemicals. Cigarette smoke falls into this category as it contains over 4,000 chemicals, many of which cause cancer.

Mutagens are mutation-causing chemicals. When organisms are exposed to a mutagen, it literally mutates their DNA, leading to cancer and other disorders. X-rays are well known mutagens.
Teratogens are chemicals that cause harm to unborn babies. The name of this toxicant comes from the Greek word teras, which means monster. These chemicals cause birth defects during development in the womb. Thalidomide was used in the 1950s as a sleeping pill and to prevent nausea during pregnancy, but turned out to be a very harmful teratogen. Even a single dose is powerful enough to cause severe birth defects in children.

Allergens are chemicals that stimulate overactivity in the immune system. When you are exposed to allergens, your body goes into overdrive, triggering an immune response to try and get rid of the allergen. This is why pollen and dust cause symptoms that are similar to being sick.

Neurotoxins are chemicals that attack the nervous system. These include heavy metals, like lead and mercury, as well as pesticides and chemical weapons. Neurotoxins can lead to symptoms like slurred speech, loss of muscle control and even death.

Endocrine disrupters are chemicals that disrupt the endocrine system in organisms and most often come from prescription drugs and chemicals in plastics. The endocrine system is also known as the hormone system, and this part of your body is what regulates growth, development, sexual maturity, brain function and even appetite.

-Toxicants that disrupt hormone functioning can lead to some serious problems because they so closely resemble real hormones in your body. Reptiles and amphibians are especially sensitive to endocrine disrupters and exposure often leads to feminization of male animals. This may seem like a lot to remember! But if you look closely, you'll see that the name of the toxicant describes the effect it has on organisms, which helps us understand these toxicants better.

Dangerous chemicals are divided into two broad categories:

 • Toxic - Poisonous-Can be general or very specific. Often harmful even in dilute concentrations.

• Hazardous - Dangerous-Flammable, explosive, irritant, acid, corrosive.

 Exposure and Susceptibility

• Airborne toxins generally cause more ill health than any other exposure (lining of lungs easily absorbs toxins)

• Largest toxin exposure reported in industrial settings.

• Condition of organism and timing of exposure also have strong influences on toxicity.

(http://fivestoneswellness.com/wp-content/uploads/2016/04/ToxicChem.preview.png)

(http://organicinsights.in/wp-content/uploads/2014/08/pic22.jpg)

(https://people.uwec.edu/piercech/Hg/Pictures/exposure1.jpg)

Excretion and Repair

• Effects of waste products and environmental toxins reduced by eliminating via excretion.

   • Kidneys (Urine)
    • Breathing

• Tissues and organs often have mechanisms for damage repair.
    • Any irritating agent can be potentially carcinogenic.

Type of Effects

• Local effects – damage at the site where a chemical first comes into contact with the body; examples are redness, burning and irritation of the skins.

• Systemic effects – adverse effects associated with generalized distribution of the chemical throughout the body by bloodstream to internal organ.

• Target organ effects – some chemical may confine their effects to specific organ; the most common organs affected by such chemicals are liver, lungs, heart, kidneys, brain and nervous system, and the reproductive system.

References:

-www.toxicologyguide.com
-en.wikipedia.org/wiki/Toxicology
-https://people.uwec.edu
-(source from my lecturer note about chapter 2)
-organicinsights.in
-fivestoneswellness.com

-noted that had been given from my lecterur Sir Mohd Jamalil Azam Bin Mustafa