[Chemistry Class Notes] on Carcinogenicity and Toxicity Pdf for Exam

Carcinogen definition can be given as the substances, radionuclide, or the radiations, which are involved directly in the formation of cancer, are known as carcinogenic substances, otherwise, as a carcinogen, and this entire process is known to be carcinogenicity.

These carcinogenic substances can damage the genome or even disrupt the cells involved in the metabolism process. Various radioactive substances are considered carcinogenic, but these substances’ carcinogenic behavior is caused by the radiation they emit. Alpha particles and Gamma rays are the carcinogens examples or examples of carcinogenic substances. Also, we have non-radioactive carcinogens such as certain dioxins, tobacco smoke, and the inhaled asbestos. 

Note: Tobacco smoke produces harmful gases such as carbon monoxide, cancer-causing substances. Often, carcinogenic substances are thought of as synthetic chemicals or chemical carcinogens, but they can be synthetic and natural in reality. These substances need not be toxic immediately, as they are insidious.

Carcinogenic Substances

Cancer is a disease group that causes abnormal cell growth to spread to other parts of the human body. It is a disease where the body cells get damaged. In general, carcinogenic substances increase cancer risk because they damage the body’s metabolic cells. Also, they damage the cell’s DNA component, which is associated directly with various biological processes in the body, leading to tumors.

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Aflatoxin B1, which is produced by a fungus, grows on the surface of peanut butter, grains, and many nuts. It is also a microbial carcinogenic substance that occurs naturally. Also, the virus hepatitis B and human papilloma can cause cancer to the person infected by them.

Besides the virus, radiations, and fungus, there are various carcinogenic substances. The substances like polynuclear hydrocarbons and benzene, which have more than two benzene rings fused together, also contain carcinogenic effects. These polynuclear hydrocarbons form when incomplete combustion of organic material like coal, tobacco, and petroleum occurs. These substances undergo biochemical reactions by entering into the human body, which damages the DNA cells and causes cancer, further leading to death.

Toxicity is the degree to which a chemical can damage the body’s human cells. We have seen the carcinogenicity effect and the substances associated with it. These are highly toxic substances in nature, and their use should be avoided to sustain a healthy body.

What is Toxicity?

Toxicity is the degree to which a chemical substance or a specific mixture of substances can lead to damage to an organism. It can refer to the whole organism’s effect, such as an animal, plant, or bacterium, and the effect on the organism’s substructure, such as an organ or cell (cytotoxicity) like the liver (hepatotoxicity). 

As an extension, the word can be metaphorically used to describe the toxic effects on more complex groups, like the family unit or society. At times, the word is less or more synonymous with poisoning in daily usage.

The central concept of toxicology can be defined as the toxic effects are dose-dependent; even water can lead to intoxication when taken in higher doses. Even a very toxic substance like snake venom, there is a dose with no detectable toxic effect. 

Recently, a novel Drug Toxicity Index (DTI) has been proposed considering the limitations of this dose-response concept. DTI involves the responsibilities like, recognizes hepatotoxic drugs, redefines the drug toxicity, predicts clinical outcomes, gives proper mechanistic insights, and has the potential as a screening tool. Toxicity is species-specific, making the cross-species analysis problematic. 

On the other side, the newer metrics and paradigms are gradually developing to bypass animal testing while maintaining the concept or feature of toxicity endpoints.

Types of Toxicity

There are four types of toxic entities, as given below:

1. Chemical, 

2. Biological, 

3. Physical,

4. Radiation:

• Chemical toxicants are inorganic substances including mercury, chlorine gas, hydrofluoric acid, and organic compounds like most medications, methyl alcohol, lead, and toxins.

• The biological toxicity of pathogens is difficult to measure because the “threshold dose” can be a single organism. Theoretically, one virus, worm, or bacteria can reproduce to cause a serious infection.

• Physical toxicants exist due to their interference and physical nature with biological processes. Examples can be given as asbestos fibers, coal dust, or finely divided silicon dioxide, which can ultimately be fatal if inhaled.

• Radiation can hold a toxic effect on the organisms.

Classification of Toxicity

Let us look at the classification of Toxicity in detail.

For the substances to be handled and regulated appropriately, they must be classified and labeled properly. Approved calculations or testing measures determine the classification. It has determined the cut-off levels set by scientists and governments (threshold limit values, no-observed-adverse-effect levels, and tolerable daily intake levels).

The pesticides provide an example of well-established toxicity labels and class systems. While currently, most countries have various regulations concerning the test types, cut-off levels, numbers of tests, the Globally Harmonized System implementation has begun unifying these countries.