Welcome to this week’s Monday Tech Talk discussing Toxicology & SDS! In this article, we dive into the fascinating world of toxicology. Understanding the potential hazards of chemicals and substances in the workplace is vital for ensuring the well-being of employees and maintaining a safe environment. Join us as we explore the importance of toxicology, how it relates to SDS, and the best practices to ensure your workplace remains compliant and secure. Let’s delve into the science behind chemical safety and equip ourselves with valuable insights for a safer working environment.

Why Toxicology:

Toxicology provides critical information and knowledge that can be used by regulatory agencies, decision makers, and others to put programs and policies in place to limit our exposures to these substances, thereby preventing or reducing the likelihood that a disease or other negative health outcome would occur.

Understanding the impact chemical substances have on the environment and living beings is crucial. Another reason why toxicology is so essential is that it studies the effects of various chemical agents on living organisms and our planet. To ensure the safety of living beings on Earth, it is critical to analyse the adverse effects of substances, also referred to as toxins. Without toxicology, scientists would not be able to identify and prevent health and ecological hazards caused by toxic chemicals.

In order to prevent toxins from accumulating in living organisms in higher concentrations, it is crucial to limit our exposure to toxic chemicals in the first place. The only way to minimize the amount of toxins we ingest or absorb through our skin is to understand the toxicity of different substances. By providing detailed information about how toxic or harmful chemicals can be, toxicology enables scientists to develop ways to limit our exposure to these substances.

How Chemicals Causes Harms:

There are only a limited number of ways in which chemicals can cause harm. Chemicals can enter and irritate the nose, air passages and lungs. They can become deposited in the airways or be absorbed by the lungs into the bloodstream. The blood can then carry these substances to the rest of the body. Ingestion (swallowing) of food, drink or other substances is another route of exposure.

Some of the effects may be delayed, in that they only manifest themselves after a extended period, which could be years following exposure. Examples include cancer and bronchitis. However, effects such as sudden death or narcosis are immediate, developing rapidly following chemical exposure. Effects may be reversible upon the cessation of exposure, as is the case with irritant contact dermatitis, or in those organs that have regenerative ability, such as the liver. The effects may also be irreversible, as is the case with the carcinogenesis and teratogenesis, persisting even in the absence of further exposure. The duration and extent of exposure together with the actual cells and tissues involved will be important factors that influence whether the effects are reversible or irreversible. Although there may be a temptation to disregard reversible effects which arise in animal studies, it is still important to consider the likely impact to humans following exposure.


There are two types of exposure Acute exposure and Chronic.

Acute exposure Acute exposures are single or multiple exposures to a relatively large dose or concentration of chemical over a short time period, typically within 24 hours. The potential effects following acute exposure to a chemical are investigated by acute toxicity testing, and any adverse effects that arise are referred to as acute toxicity.

Chronic exposures are prolonged exposures (i.e. months or years) to a much smaller concentration or dose of chemical compared to acute exposures. Any subsequent “chronic toxicity” is the result of cumulative damage at specific target organs/systems. However, not all chemicals to which we are chronically exposed are harmful and, in some cases, they are essential for our well‐being. For example, we need to be “chronically exposed” to both salt and vitamins over our entire life span; otherwise, we will suffer from ill health. However, as previously mentioned, acute exposure to either of these could cause harm. Finally, it should be noted that some chemicals may give rise to both acute as well as chronic effects. For example, acute inhalation of a high concentration of benzene vapor will give rise to narcosis, headache, etc., whereas prolonged exposure to benzene will increase the risk of developing cancer.


Before any absorption can occur, the substance must cross a biological cell membrane. This is the interface between the cell and its immediate external environment.

Absorption by the Oral Route

The process by which a dissolved drug crosses the intestinal wall from the GI fluid into the portal vein. Route of administration whereby a substance is taken through the mouth, swallowed, and then processed via the digestive system

Absorption by the Inhalation Route

This is a perfect setup for airborne chemicals that are able to reach the alveoli and get into the blood stream.

Absorption by the Skin

The outermost layer of the epidermis, called the stratum corneum, is an effective barrier to water‐soluble chemicals However, although lipophilic substances are able to penetrate the stratum corneum, they need to be able to reach the lower dermal layer of the skin if they are to become systemically available.

Dermal absorption happens when a chemical goes through the skin and travels into the body. Many chemicals used in the workplace can damage organs if they penetrate the skin and enter the bloodstream

Absorption by Other Routes – Intravenous and Intraperitoneal Routes

While inhalation, oral, and dermal routes are probably the most common exposure routes encountered both in the workplace and home life, there are other routes that are useful to mention. These include the intravenous and intraperitoneal routes. Exposure by the intravenous route, that is, administration of the test substance directly into a vein, means that it gets directly into the blood stream. This avoids the issue of absorption and first‐pass metabolism, meaning that it is 100% bioavailable.

Intraperitoneal injection is where the substance is injected directly into the peritoneal cavity. Absorption is relatively rapid, owing to the large surface area and excellent blood supply. However, in this case absorption is through the hepatic portal vein, and the test chemical will pass through the liver, undergoing first pass metabolism prior to reaching general circulation. The intraperitoneal route is useful in that it avoids long residence time in the gastrointestinal tract and any potential for hydrolysis

Presented by: Keabetswe Maubane

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