Hazardous Chemicals

writer Zeynep Aktas

Health Hazards

Chemicals are a part of our lives and we encounter chemicals in every aspect of our lives. For this reason, we need to recognize chemicals, know how to use them and, if necessary, how to avoid them. This information does not only affect us individually, but it is also our social responsibility.

In many foods, health products and cosmetic products that we use and consume unconsciously, there may be some chemicals that will adversely affect our lives and our environment. For this reason, it is very important that we be aware of dangerous chemicals. Let's take a brief look at these chemicals.

Read: Chemicals Found in Cosmetic Products and Their Hazards to Health

The impact of health hazards was known for a long time. However, in ancient times, the effects of these dangers and the ways of protection were not known as today. Some dangerous substances were even used for therapeutic purposes (for example, in the 19th and 20th centuries). arsenic as a metabolism booster, was given to patients for weight loss purposes, likewise in the 19th century in certain pills and syrups that contain mercuryIt was used to treat depression, toothache, and birth control).

old drugs

Figure 1. Some drugs used in the nineteenth century (Source: medicalbag)

Today, learning to protect from these dangers and using these substances carefully has become a necessity as the population increases and we use chemicals in every field. As a result of this necessity, it is a study that examines the behavior of living creatures against chemical substances. pharmacology ve toxicology sciences emerged.

General Toxicology of Chemical Substances

Toxicity (poisoning effect): It is the action of a chemical compound or element in a way that disrupts normal functions in a biological system. For this reason, the damage to health does not depend only on the physical or chemical properties of the chemical substance. It also depends on the organism exposed to the substance, the sex and age of the person.

The health risks of some chemicals have been known since ancient times. In the last 150 years, chemists have studied and learned chemicals containing toxic active substances.

Chemical substances in the human organism acute or chronic toxicity, irritation, irritation, sensitization of the body, cancer, reproductive and birth risks It may cause adverse effects such as.

To determine the acute toxicity of a substance in-vivo experiments and LD50 values ​​are determined. The LD50 is data in mg per kg body weight taken once and is the dose that causes the death of 14% of the experimental animals after 50 days. This dose also depends on the exposure and breed of animals. In addition, the LC50 value, which indicates the lethal concentration value taken into the body by inhalation, can also be used.

What is LC50?

LC50 is the amount of harmful substances in the air in mg/L and is the dose that usually causes the death of 4% of the experimental animals after 50 hours of inhalation. In Table 1, values ​​indicating the toxicity of chemical substances are given.

Table 1. Toxicity degrees of chemical substances, criteria, test environments and poisoning amounts

toxicity levels of chemicals

The interaction between the toxic substance and the organism takes place in 4 steps.

1. Exposure to and ingestion of the compound,

2. Distribution of the compound in the organism,

3. Metabolism (conversion) of ingested compounds,

4. Elimination of the compound.

In practice, the toxicity of a product is indicated by the dose taken. The toxic substance can be ingested through the respiratory tract, digestive tract, or skin and inflammations. However Respiration is the most important way of taking toxic substances into the body.. Oral or skin contamination is easily avoided.

What is Maximum Working Concentration MCD? 

The concentration of toxic substances in the working air must be known in order to prevent respiratory damage. The highest concentrations that will not harm health are called maximum working concentration MCD. The MCD is defined as the highest concentration of gas, liquid or particle in the air that is not harmful to health as a result of inhalation for eight hours a day.

Since we have briefly acquainted with dangerous chemicals and the ways to identify them, we will write about them in our next articles. carcinogenic, teratogenic and mutagenic substances Let's take a look at how to protect ourselves from them.

Until then, stay healthy.


  • Canel, M. and Canel, E. 2016. Laboratory Safety. Gazi Publishing House, 142 and 172-178 p., Ankara.

About the Author

Zeynep Aktas

Born in 1998, a Chemical Engineer who believes that science will save the world and works to become a scientist.

Visit on LinkedIn