Chemicals that are used to kill insects are generally called insecticides. Insecticides have a wide application in the field of medicine, agriculture, and industry. The possibility of disturbing ecosystem components predominantly can be found among insecticides and are toxic to animals as well as humans. Some insecticides become concentrated when they spread in the food chain.
Pesticides are chemical substances intended to kill pests. Generally, a pesticide is a chemical or a biological agent such as a virus, bacterium, antimicrobial, or disinfectant that deters, incapacitates kills, pests.
Types of insecticides
There are three kinds of insecticides as follows:
- Systemic Insecticide: It is a kind of insecticide that is applied into the soil so that it can seep easily to the roots of the plant. When the insecticide has soaked into the roots, it moves to outer parts like leaves, fruits, flowers, twigs, stem, and branches. It forms a thin film on the surface area of the plant. It acts like poison to any insect. This surface area protects the plant from chewing by an insect coming to munch the plant.
- Ingested Insecticide – Some examples of ingested pesticides are rat, roach and many more.
- Contact Insecticide – These types of insecticides act like bullets. These bullets aim only at a particular target to kill insects by their application. Generally, household insect spray works like contact insecticides as if it directly hits the insect that is in the target.
Classification of Insecticide based on:
- Chemical composition: This insecticide is classified as organic and inorganic.
- The mode of entry in the insects: This insecticide is classified as contact poisons, fumigants poisons, stomach poisons, and systemic poisons.
- The mode of action: This insecticide is classified as physical poisons, nerve poisons, respiratory poisons, protoplasmic poisons, general poisons, and chitin inhibitors.
Toxicity: It is classified into four types:
- Extremely toxic – Colour: red, symbol: skull and poison, oral LD50: 1-50
- Slightly poisonous – Colour: blue, symbol: danger, oral LD50: 501 – 5000
- Very toxic – Colour: yellow, symbol: poison, oral LD50: 51 – 50
- Practically nontoxic – Colour: green, symbol: caution, oral LD50: >5000
- The specificity stage. This pesticide falls under ovicides, pupicides, larvicides, and adulticides.
Types of pesticides
Pesticides can be seen as:
Biodegradable:
Those pesticides that can be degraded by microorganisms and other living things to non-harmful chemicals are referred to as biodegradable
Persists:
The persistent types are those which might take months or years to degrade.
Another way of classifying these is to consider those which are chemical forms or derived from a common source or production method.
Chemically-related pesticides:
Organophosphate :
Most organophosphates are pesticides, they work in the body by interfering with the activity of the enzyme which regulates a neurotransmitter.
Carbamate:
The carbamate pesticides just like the organophosphorus pesticides also work by interfering with the nervous system but their effects on an enzyme regulating the neurotransmitter are usually reversible.
Organochlorine insecticides:
They were widely used in the past, but many countries have prohibited the application of organochlorine insecticides because of their health and environmental effects and their persistence. Examples include DDT, chlordane, and toxaphene .
Pyrethroid:
These are synthetic pyrethrin analogs, a natural pesticide obtained from chrysanthemum(Flower). These were designed to provide a maximum persistence of these compounds in the environment.
Sulfonylurea herbicides:
This class of herbicides has been commercialized for weed control including pyrithiobac-sodium, cyclosulfamuron, bispyribac-sodium, terbacil, sulfometuron-methyl Sulfosulfuron, rimsulfuron, pyrazosulfuron-ethyl, imazosulfuron, nicosulfuron, oxasulfuron, nicosulfuron, flazasulfuron, primisulfuron-methyl, halosulfuron-methyl, flupyrsulfuron-methyl-sodium, ethoxysulfuron, chlorimuron-ethyl, bensulfuron-methyl, azimsulfuron, and amidosulfuron.
Biopesticides:
There are certain types of pesticides called biopesticides derived from such natural materials as animals, plants, bacteria, and certain minerals.
Harmful effects of insecticides and pesticides on human health
All these contain pesticide residues-fresh fruits and vegetables, processed foods, water, air, and soil. Acute and chronic health effects from dietary exposure and agricultural pesticides are serious public health concerns, especially in developing countries. Chemical pesticides can be carcinogenic, cytotoxic, and mutagenic to human health. Because pesticides mode of action is not specific to a single species, they often eliminate or damage organisms other than pests, including humans. A WHO and United Nations Environment Programme report shows that globally, three million people are poisoned while 200,000 die from pesticides. Most of the incidents occur in developing countries.
Pesticides cause reactive oxygen species, and these significantly lower the level of antioxidant and its cellular ability to protect the cell from oxidative damage. This imbalance leads to the impact on signaling pathways of proteins, lipids, and nucleic acids as well. Reactive oxygen species and oxidative stress cause long-term health effects.
Pesticides are commonly applied with low precision which results in many adverse human health impacts which range from acute intoxication to chronic diseases that include various kinds of cancer (brain cancer, breast cancer, prostate cancer, bladder cancer, and colon cancer), Alzheimer’s disease (AD) ,Parkinson’s disease, neurotoxicity, infertility,leukemia and diabetes.
Pesticides, however have various benefits to agricultural productivity. They aid in growing crops yield since they minimized losses from attacks of pests, diseases, and weeds. They further help in food security through protection of the quantity and quality of crops obtained. In public health, pesticides are used to control the population of disease-transmitting insects such as ticks, mosquitoes, and fleas; these prevented several diseases, for example, dengue fever, malaria, and Lyme disease. Although it is well established that agrochemicals play a role in increasing agricultural production, the trade in pesticides of the developed world has experienced tremendous growth in the production and development of environment-friendly pesticides with different formulations such as powder, solution, and emulsifiable concentrates. However, the use of pesticides must also be balanced with the environment and health considerations, and pesticide practice must be responsible so that effective, sustainable methods for controlling pests are assured by promoting examples such as integrated pest management.
