Chapter 19: Chemicals used in Daily Life

Different types of chemicals are used in our daily life. Some are natural and some are manufactured in industries — for example chemicals used for cleaning, food preservatives, pesticides, chemicals used to preserve fruits and vegetables, and chemical fertilizers.

Industrial chemistry is the branch of chemistry in which we study the different aspects of transformation of matter to manufacture materials useful to mankind through chemical processes.

Common chemicals used in daily life: detergent, sugar, soap, salt, insecticide spray, and rat poison.

Food gets decayed due to the growth of bacteria, yeast, and mold on it. Substances used to protect food from decaying are called food preservatives.

They are used to prevent food from decaying for a long time — cereals, legumes, vegetable products, fruits and vegetables, and animal products like meat, milk and milk products. Food preservatives check the growth of bacteria, yeast, and mold in food.

Very Important for SEE: Food preservatives are of three types — chemical food preservatives, natural food preservatives, and preservatives that induce ripening of fruits.

Salt and oil control the growth of microscopic germs and organisms. Chemicals like sodium benzoate, sorbate, sulphur dioxide, nitrates and nitrites, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), calcium propionate, and sodium metabisulfite are also used as food preservatives.

Common chemical food preservatives (sodium benzoate, sorbate, propionates) and natural preservation methods (lemon juice, vinegar, salt curing, freezing).

Natural food preservatives come from organic matter (plants, animals, fungi and algae) and prevent food materials from decaying. Examples: mugwort (Titepati), neem oil, lemon concentrate (Chuk).

Traditional natural methods of food preservation include drying in the sun, keeping in cold places or above water, use of wood ash, and mixing turmeric with oil. Modern methods include pasteurization, freezing, and keeping food in cold stores. All these methods control the conditions microbes need to grow.

Fruits like mango and banana take a long time to ripen even after maturation, so chemicals are used to induce fast ripening. These chemicals are called ripening agents. Examples: calcium carbide, ethylene gas, ethephon.

A chemical ripening agent (calcium carbide sachet) being used to ripen mangoes.

Traditional ripening methods include wrapping fruits in a jute sac, using Asuro (Malabar nut) leaves, keeping fruits in a pit covered with soil, or wrapping them in husk or hay.

SEE Focus: Calcium carbide is used excessively nowadays because it is cheap and easy, but overuse can cause skin irritation, skin burning, red blisters, lung effusion, and eye irritation. It should be used carefully and never in excess.

Reetha (soapberry), Peena (mustard seed cake), wood ash, lemon juice, and Sajiban are natural materials used for cleansing purposes.

Natural materials used for cleansing: reetha (soapberry), peena (mustard seed cake), wood ash, and sajiban leaves.

Reetha contains saponin, which acts as a foaming agent, so it can be regarded as a soft natural soap. It has been used for centuries to clean the body and wash clothes, and is a traditional medicinal tree found in Nepal, India, and China. Its powdered fruit is used in shampoo as a foaming agent.

Peena has long been used in Nepal to wash hair and make it soft and strong. It contains nutrients important for healthy hair growth, such as folate, niacin, thymine, and vitamin B6 (forms of vitamin B complex). Its use can control hair fall and keep hair soft and healthy.

Wood ash mixed with a little water forms a paste that works as an abrasive cleaner. It can brighten metals, clean dirty utensils, and remove sticky residue and adhesive. It is also a good source of potassium, phosphorus, and magnesium for plants, so it can be used as a fertilizer.

Sajiban (Jatropha curcas) is a useful plant found naturally in different regions of Nepal. Animals do not eat it, so it can be used as a fence. Its leaves make compost manure, its juice cures burns, it can be used as anticancer medicine, and its twigs are used for brushing teeth. It is a good source of nitrogen, phosphorus, and potash, so it is also used as an organic fertilizer.

Lemon juice contains citric acid in high concentration. It is a good natural cleaner due to its low pH value and antibacterial properties, and it also works as a natural bleach. It cleans without damaging wood or clothes, cleans copper surfaces efficiently, and has been used as a medicine for decades.

The sodium or potassium salts of long chain fatty acids are called soap. Animal fat or vegetable oil, sodium hydroxide, and sodium chloride are the raw materials for making soap.

The process of making soap by the hydrolysis of vegetable oil or animal fat with alkali is called saponification.

Diagram of the soap-making process: mixing oil with NaOH, heating, and separating soap crust from glycerol.

Detergent is a substance used to clean clothes. It is a chemical obtained from hydrocarbons that is more soluble in water than soap, so it is also known as soapless soap.

Detergent powder, a soapless synthetic cleaning agent used to wash clothes.

Poisonous substances used to remove, destroy, kill, and control harmful pests from seeds, plants, trees, birds, animals, human health, and construction areas are called pesticides.

According to the Pesticide Management Act 2076 (B.S.), 'pesticide' means any organic, vegetation, biological, or chemical material used to protect plants, agricultural products, forests, living beings, livestock, human health, storage, packaging, and construction works from harmful disease, insect, mite, nematode, weed grass, and rodents.

SEE Focus: DDT was first imported to Nepal in 1952 AD to control malaria. The average use of pesticides in Nepal is about 396 grams per hectare. About 80% of used pesticides get mixed into the soil and take a long time to diffuse, destroying soil microorganisms and risking pollution of surface and underground water.

On the basis of effect on the environment, the pests they affect, and mode of action, pesticides are classified as follows.

A farmer spraying chemical insecticide on crops in a field.

Safe storage of pesticides: a locked, labelled, ventilated pesticide storage cabinet with warning signs.

Environmental pollution causes trouble for humans and all living beings in their survival. It degrades the quality of environmental components like air, water, and soil, causing imbalance in the ecosystem.

Chemical pollution: foamy, discoloured wastewater from industrial and chemical discharge flowing into a stream.

Pollution causes negative impacts such as airborne disease transmission (air pollution) and waterborne disease transmission (water pollution). Increasing carbon dioxide from air pollution also raises the average temperature of the earth.

Different pesticides used to kill insects, pests, and rodents contain poison and kill useful insects along with harmful ones, creating imbalance in the ecosystem. DDT (Dichlorodiphenyltrichloroethane) causes physical and biological environmental pollution.

Health effects of pesticide exposure: skin irritation/blisters on hands and a diagram comparing a normal lung with an asthmatic lung.

Insecticides and chemical fertilizers reach water sources through rainwater and affect ecosystems there, destroying aquatic animals. Chemicals like insecticides, fungicides, and weedicides pollute soil, and substances like DDT, aldrin, dieldrin, and parathion degrade soil quality.

SEE Focus: Aldrin, Dieldrin, DDT, BHC, Chlordane, Lindane, and Endosulfan are all banned in Nepal. Production, buying, selling, export, and import of Dichlorvos insecticide is restricted in Nepal.

The haphazard use and disposal of industrial chemicals like cement, ceramics, glass, plastic, fiber, chemical fertilizers, soap, and detergent has degraded environmental quality and caused ecosystem imbalance. They should not be disposed of directly into water sources or agricultural land.