What Are Pesticides and Are They Dangerous?

Table of Contents
1. What are Pesticides? Range of Pesticide Classifications
2. Potential Health Concerns Associated With Pesticides
3. Pesticide Use and Potential Exposure
4. You Could Be Genetically More Sensitive to Pesticides

What are pesticides? If you guessed that pesticides are used to kill pests, you’d be correct. Since humans share the world with animals and critters, it’s common to encounter these pesky critters or rodents even in the comfort of your own home. You may have had to spray an insecticide to destroy a colony of ants, use a rodenticide to kill an unwelcome rat, or hire a pest-control specialist to get rid of termites.

By nature, pests commonly carry pathogens, bacteria, and germs that harm human health. Hence, humans rely on pesticides to prevent pest multiplication and the potential damage they could inflict on humans, including property and produce that humans consume which may have chemical residues. Pesticides come from the Latin root word “cida” or ‘to kill’. And as its name suggests, pesticides are used to kill pests.

What are pesticides, and are they a modern-day substance? Contrary to popular belief, the  pesticides commonly found in today’s hardware stores or home goods stores are not recent inventions. In fact, ancient civilizations utilized some form of pesticide to keep their crops pest-free. For instance, ancient Sumerians placed elemental sulfur on their plants to keep bugs at bay. Similarly, Medieval farmers used chemicals like arsenic or lead for their crops, while the Chinese used arsenic and mercury compounds. Even the Greeks and Romans relied on sulfur, ash, and oil to protect crops, livestock, and even their own bodies from pests. You can think of the latter as akin to today’s mosquito or lice repellant.

As you can see from the examples above, all pesticides are not created equal, which means not all pesticides are that dangerous. Some herbed-based pesticides are safe, as they’re all-natural and free from toxins. What are pesticides that are considered dangerous? Some pesticides must be used with extreme caution with warning labels such as “dangerous” or “poison” stamped onto the container because of their high toxicity levels. It all boils down to the active ingredients used to control the pest in the pesticide. Learn more about pesticide use, especially as a homeowner dealing with potential infestations that could impact health or as a crop consumer who frequently eats fruits and vegetables since pesticides are commonly used in agriculture.

What are Pesticides? Range of Pesticide Classifications

Pesticides could be any substance or mix of substances that are meant to kill, destroy, eradicate or control pests. Doing so helps mitigate the spread of disease, and promotes livestock or plant growth, which are commonly used for human consumption. Pesticides are often classified based on their toxicity levels, what they kill, their biodegradability, and chemical composition. Take a look at the classifications of pesticides below:

Toxicity Levels

The World Health Organization (WHO) classifies pesticide toxicity levels into four categories. The classification is based on the technical grade of active ingredients in the pesticides. The classification are as follows:

  • Class I-a: extremely hazardous
  • Class I-b: highly hazardous
  • Class II: moderately hazardous
  • Class III: slightly hazardous

Pests Killed

  • Insecticides-insects
  • Rodenticides-rodents or rats and mice
  • Herbicides-herbs or plants
  • larvicides-larvae
  • Bactericides-bacteria
  • Fungicides-fungus or fungi


Pesticides can also be classified on how biodegradable are its components. Take a look at them below:

  • Biodegradable: As the name suggests, these pesticides can be readily broken down by microbes and other living beings that aid in decomposition. Often, these pesticides could be broken down into harmless compounds. These are generally seen as more acceptable than chemical ones. Examples are herbal concoctions used in protecting crops against insects.
  • Persistent: If biodegradable is easy to break down, persistent chemicals will take many months or even years to process. These persistent substances could have harmful impacts and lasting biological effects on those who handle them. So it’s best to proceed with extreme caution when handling these persistent pesticides.

Chemical Composition

Finally, pesticides can be classified based on which chemicals they are derived from during production. In general, natural chemicals from plants are far more healthy for humans than synthetic counterparts.

However, pest-control specialists assert that some lab-made chemicals are more effective in dealing with pest infestations than their all-natural counterparts. It’s a tricky situation because you want to eradicate the harmful pests, but at the same time, you also don’t want to be exposed to toxic substances that could adversely impact your health. Here are the most common chemical pesticides in the market:

  • Organophosphates: Most made with these substances are insecticides. Sadly, they affect the human nervous system. Exposure could disrupt enzymes that regulate neurotransmitters.
  • Carbamate: It is similar to the chemical above as it also disrupts the enzyme that regulates neurotransmitters of the nervous system. But this is thankfully reversible with decreased exposure and medication (if needed).
  • Pyrethroid: This is pyrethrin’s synthetic version. Pyrethrin is commonly found in the chrysanthemum flower. The natural variant is less stable while the synthetic one was specially formulated to maximize stability.
  • Organochlorine: These insecticides were popular in the late 19th century. Examples are DDT, toxaphene, and chlordane. Many countries have banned these due to their environmental and health impacts. They’re also extremely persistent and hard to biodegrade. If this is still being used in your country, beware. It’s vital to read the ingredient list to protect your health.
  • Herbicides: There are many variants of herbicides usually relying on sulfonylureas. They have been mass-produced to control the weed. However, excessive use could impede the reproduction of other plants and affect plant mortality.
  • Biopesticides: These are derived from natural materials like bacteria, minerals, plants, and even animal raw materials.

Potential Health Concerns Associated With Pesticides

For pesticides to be effective, they often contain active ingredients to kill or control pests. Pesticides are typically released into the environment, resulting in environmental pollution with contamination in air, ground or soil, and water. Some of these pest killers can wipe out other animals and insects that are not the intended target of the pesticide, resulting in a biological imbalance.

Furthermore, most of these substances are also toxic to humans. Improper use and exposure could lead to oxidative stress, allergic reaction, irritation, swelling, or in extreme cases, even death. Some pesticides are highly lethal or poisonous to humans. Often, pesticides are categorized based on their toxicity levels with a range of I being the most lethal to humans to III being the least dangerous.

Since pesticides contain ingredients that harm the pest population they intend to control, pesticides could be potentially hazardous to humans, animals, and even the environment. Thus, if you use pesticides at home or come in contact with them regularly for work, you have to understand what you’re using. Take note of the chemical’s toxicity levels and potential adverse health effects. You should also take preventive measures to minimize exposure to the pesticide products you use.

Acute Exposure

The four routes of exposure to these chemicals are through dermal contact via the skin, inhalation through the nose, oral pathway or ingestion in the mouth, and contact with the eyes either by splashed droplets, aerosol particles, or rubbing contaminated fingers on the eyes. Hazards or potential injuries are determined by the pesticide’s toxicity levels and the amount of exposure. For example, a farmer inhaling fumes from an insecticide will recover faster than a toddler who accidentally swallows the same material. These are the most common, immediate, and ill effects of using pesticides:

  • Respiratory issues especially for people with rhinitis and asthma
  • Blisters, rashes, and other skin issues
  • Swelling and stinging of the eyes with redness and irritation
  • Nausea
  • Vomiting
  • Headaches or dizziness
  • Abdominal pain
  • Diarrhea

Notably, the symptoms above are for acute exposure, meaning one-time accidental misuse of pesticides and not lasting longer than a day.

Chronic Exposure

Those who are repeatedly exposed to certain chemicals, even in small doses, over a period of time, are more at-risk for associated health problems. Those who regularly handle pesticides for work could suffer more serious and long-lasting impacts, such as the following:

  • Vision problems
  • Lung damage
  • Heart failure
  • Toxicity to fetal development resulting in birth defects
  • Reproductive health impacts like low sperm count or non-viable eggs
  • Genetic changes
  • Immunotoxicity
  • Blood disorders
  • Development of benign or malignant tumors (resulting in cancer)
  • Neurological disorders like Parkinson’s Disease, nerve disorders resulting in issues like tremors or poor balance
  • Disruption of endocrine function

Pesticide Use and Potential Exposure

If you’ve been wondering, What are pesticides, and are they dangerous? Your curiosity is you being responsible for your health. You may be unknowingly exposing yourselves to pesticides if you consume produce and livestock treated with FDA-approved pesticides. The FDA enforces the tolerances established by the EPA (Environmental Protection Agency) with regards to pesticide residue amounts permitted to legally remain on human food and animal feeds. If this is a concern, opt for organic produce and make it a point to wash veggies thoroughly.

On top of that, no one wants pests in their home. So you could be exposed to pesticides to keep unwanted pests away, especially if you live in an area that’s prone to seasonal pest infestations. If you’re using a certain pesticide, take note of the active ingredient as this is the compound responsible for controlling the pest. Again, pesticides have varying toxicity levels based on this active ingredient. To mitigate potential hazards, select a pesticide with the lowest toxicity.

Moreover, it would help to use proper application methods to reduce chemical exposure. Make it a point to always read the labels and follow the instructions. Use protective equipment like a face mask, lined gloves, and goggles as these promote the safest handling of chemicals, reducing respiratory, dermal, and eye exposure. Store your chemicals in a safe location, keeping them away from your children’s reach.

You Could Be Genetically More Sensitive to Pesticides

If you’re feeling ambivalent about the use of pesticides or your potential exposure in produce, you can take a CircleDNA test as this at-home DNA test reveals if you are genetically more sensitive to pesticides. (This report is just one of hundreds of reports about yourself you’ll learn through this DNA test.)

Those who have a genetically higher pesticide sensitivity have an increased risk of developing respiratory, neurological, or gastrointestinal issues with pesticide exposure. With this increased risk, you can make a conscious effort to purchase only organic, pesticide-free produce.

And, of course, you must stay even more vigilant with the safe handling of pesticides if you ever need to use them in your home. You could stick to biological and green pesticides or seek the help of a professional pest control firm to help with your pest issues.


  1. Pesticides Classification and its Impact on Environment (Rajveer Kaur1, Gurjot Kaur Mavi & Shweta Raghav) https://www.ijcmas.com/8-3-2019/Rajveer%20Kaur,%20et%20al.pdf
  2. The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 2019 (World Health Organization) https://apps.who.int/iris/bitstream/handle/10665/332193/9789240005662-eng.pdf?ua%3D1
  3. Pesticides (The Food and Drug Administration) https://www.fda.gov/food/chemicals-metals-pesticides-food/pesticides
  4. 8 – Pesticides (Randy D. Horsak, Philip B. Bedient, M. Coreen, Hamilton F. & Ben Thomas) https://www.sciencedirect.com/science/article/pii/B9780125077514500306

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