Toxicology

By Mia Golosino 8R

Toxicology is a topic shared between chemistry and biology. It is the study of toxic chemicals that are harmful to living organisms.

Toxicologists identify the negative effects of substances depending on their two main factors: routes of exposure (meaning how it entered the body or organism) and dose (the duration of exposure and concentration of the substance). Substances could have potentially been inhaled, ingested, injected or absorbed through the skin or eyes. Dosage is the factor that indicates the quantity and speed of exposure. Minimal concentration but continuous exposure is a chronic dosage whereas the opposite - a large, single exposure - is an acute dosage. Although dosage and routes of exposure are the two main factors, species, environment, health, age, sex and personal characteristics also play parts in the toxicity assessment. These are required because the quantity of the substance in the body is measured in mg/kg, mg/cm^2 or mg/m^2.

There are three ways to analyse toxicity; vivo, which is using a whole animal; vitro, which is the use of isolated tissues and cells and finally silico, which is through computer simulation. The first two methods are unpopular due to awareness of animal well being and chemical residues such as pesticides. “In Silico Technology” or IST is used instead.

IST allows toxicologists to visualise and predict toxicity without using the vivo and vitro methods. These visualisations and predictions are shown in encoded models with information from experimental data and structure-activity relationships (the 3D structure of a molecule and its biological activity).

Different toxicity testing methods would now lead us to different types of toxic substances. As well as poisons, there are also carcinogens, mutagens and teratogens. Carcinogens are compounds that are capable of causing cancer when they disrupt the healthy rate that cells go through to produce new ones. This cycle is strictly controlled so if carcinogens were to mutate the genes controlling the cell divisions, it would cause the cells to escape the normal cycle and create a tumour. Carcinogens can be found in cigarettes, processed meat and alcoholic beverages.

A mutagen is a type of radiation or a chemical substance that causes genetic mutations, just like carcinogens. In fact, carcinogenic chemicals such as benzene, toluene and asbestos are a type of mutagen. Solar UV radiation, cosmic radiation and radioactive radiation are all mutagens. The difference between mutagens and carcinogens is that the latter affects the body through inhalation and ingestion whereas the former’s exposure route is absorption of the skin.

Teratogens are different to carcinogens and mutagens in the sense of the effect, but their exposure routes are a mix of both: absorption, inhalation and swallowing through a pregnant woman.

Poisons, unlike the previous three chemical substances, can be synthetic or manufactured. However, some of the most lethal poisons are bacteria. Toxins are produced within living organisms. Venom is a type of toxin, as the venom from a spider bite.

There are still many types of poisons and toxic chemicals, but it would be easier for a toxicologist to describe these. The chemical’s physical state, exposure routes, dosage, the health of the victim, their sex and personal characteristics can all change the effects of a toxic substance because of the ratio of poison to victim weight, the duration of reaction time and effectiveness of the chosen method, whether it be chronic or acute.

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