Pesticides are used around the world to control insects, weeds, fungi, rodents, and other organisms that can damage crops, spread disease, harm structures, or interfere with homes and businesses.
They also raise an important water-quality question: what happens when pesticides move beyond the area where they were applied?
Depending on the chemical, soil, weather, application method, and local geology, some pesticides can move into streams, lakes, or groundwater that may ultimately serve as drinking-water sources.
Quick answer: “Pesticide” is a broad category, not one type of chemical. Different pesticides have very different properties, toxicity, persistence, and environmental behavior. Some can reach drinking-water sources through runoff, leaching, spills, or improper handling. Whether that poses a health risk depends on the specific pesticide, its concentration, toxicity, and the amount of exposure.
This guide explains what pesticides are, the major pesticide categories, how they can reach drinking water, how exposure risk is evaluated, and what homeowners can do if pesticide contamination is a local concern.
In This Guide
- What Is a Pesticide?
- Active and Inert Ingredients
- Major Types of Pesticides
- Hazard, Toxicity & Risk
- How Pesticides Enter the Environment
- How Pesticides Reach Drinking Water
- How to Test for Pesticides
- Water Treatment Options
- Reducing Pesticide Exposure
- Berkey® Filters and Pesticides
- Frequently Asked Questions
What Is a Pesticide?
A pesticide is a substance or mixture intended to prevent, destroy, repel, or control a pest.
The word pest covers much more than insects.
Depending on the product, the target may be:
- Insects
- Weeds
- Fungi
- Rodents
- Mites
- Algae
- Snails or slugs
- Other unwanted organisms
Pesticides are used in agriculture, homes, gardens, public-health programs, commercial buildings, parks, golf courses, forests, and many other settings.
Pesticides are not all volatile organic compounds. Some pesticide ingredients may be VOCs, but many are not. Likewise, substances such as arsenic are elements and should not be classified as VOCs.
Active Ingredients vs. Inert Ingredients
Pesticide products can contain both active ingredients and other ingredients traditionally called inert ingredients.
Active Ingredients
The active ingredient is the component intended to produce the pesticidal effect.
Depending on the product, it may:
- Kill a pest
- Repel it
- Interrupt its development
- Prevent unwanted plant growth
- Control another biological process
Inert or “Other” Ingredients
Other ingredients may perform functions such as:
- Acting as solvents
- Helping ingredients mix
- Improving spreading or adhesion
- Serving as carriers
- Adding fragrance or color
- Improving product stability
- Acting as aerosol propellants
“Inert” does not mean harmless, inactive, or nontoxic. In pesticide regulation, the term primarily means that the ingredient is not the active pesticidal ingredient. Its toxicity and risk must be considered separately.
What Are the Major Types of Pesticides?
Pesticides are often categorized according to the organism or problem they are designed to control.
| Pesticide Type | Primary Target | Common Uses |
|---|---|---|
| Insecticides | Insects | Agriculture, homes, structural pest control, mosquito management |
| Herbicides | Unwanted plants and weeds | Crops, lawns, roadsides, landscaping |
| Fungicides | Fungi | Agriculture, plants, seeds and other approved uses |
| Rodenticides | Rodents | Homes, farms, businesses and pest-control programs |
| Larvicides | Immature insect stages | Often used in mosquito-control programs |
| Algicides | Algae | Water-management and other approved applications |
Insecticides
Insecticides are designed to control insects.
They can be formulated as:
- Sprays
- Baits
- Granules
- Dusts
- Aerosols
- Other application forms
Different active ingredients act through distinct biological mechanisms and exhibit varying environmental and toxicological properties.
Herbicides
Herbicides are designed to control unwanted plants.
They are widely used in agriculture and landscaping and may be applied before weeds emerge, after they emerge, or selectively to particular plant species depending on the product.
Application should follow the product label. There is no general rule that spraying an herbicide directly onto plants is always the “safest” approach.
Rodenticides
Rodenticides are designed to control rats, mice, and other designated rodents.
Because some rodenticides can also be hazardous to children, pets, wildlife, and non-target animals, proper placement and label compliance are especially important.
Fungicides
Fungicides control fungal diseases affecting plants and crops.
The term also appears in other regulated products, but agricultural fungicides should not be confused with antifungal medications intended for humans.
Larvicides
Larvicides target immature stages of insects.
They are particularly important in mosquito management because treating aquatic mosquito larvae can reduce the number that develop into adults.
Larvicides do not kill “rodent larvae.” Rodents are mammals and do not have a larval life stage.
Pesticide Hazard, Toxicity, and Risk Are Not the Same Thing
It is easy to describe pesticides simply as either “safe” or “dangerous,” but that is not how toxicology works.
Risk depends on two major factors:
- Toxicity: how capable the substance is of producing harm.
- Exposure: how much of the substance reaches a person, by what route, and for how long.
A useful principle is: a highly toxic pesticide may pose little practical risk if exposure is effectively prevented, while even a relatively low-toxicity product can cause harm if exposure is sufficiently high.
Exposure can occur through:
- Swallowing
- Inhalation
- Skin contact
- Eye contact
Acute Exposure
Acute poisoning refers to effects following a relatively large exposure over a short period.
The symptoms differ significantly among pesticides.
Depending on the chemical and dose, acute poisoning can involve:
- Nausea or vomiting
- Headache
- Dizziness
- Eye or skin irritation
- Breathing problems
- Neurological effects
- Other organ-specific effects
Severe pesticide poisoning can be life-threatening.
Long-Term Exposure
Long-term health effects are also chemical-specific.
Some pesticides have raised concerns involving:
- Nervous-system effects
- Reproductive or developmental effects
- Endocrine-related effects
- Cancer
- Other chronic health outcomes
That does not mean every pesticide causes all of these effects.
Risk assessment has to evaluate the specific active ingredient, dose, route, exposure duration, and evidence available for that chemical.
Are Natural or Organic Pesticides Automatically Safer?
No.
A pesticide derived from a plant or a naturally occurring material can still be biologically active and potentially harmful at sufficiently high exposure levels.
Likewise, a synthetic pesticide is not automatically more hazardous simply because it was manufactured chemically.
The more useful questions are:
- What is the active ingredient?
- How toxic is it?
- How will it be used?
- What exposure could occur?
- What does the label require?
For example, pyrethrins are naturally derived insecticides, while pyrethroids are synthetic compounds modeled on pyrethrin chemistry. Both groups can have environmental and human-health considerations depending on the specific compound and exposure.
Avoid broad statements that an entire pesticide family has “little to no effect on human health.” Risk varies substantially within pesticide classes and according to exposure.
How Do Pesticides Enter the Environment?
Once applied, a pesticide does not necessarily remain exactly where it was placed.
Its environmental movement depends on:
- Chemical properties
- Soil composition
- Rainfall
- Irrigation
- Temperature
- Application method
- Rate of degradation
- Topography
Runoff
Rainfall or irrigation can carry pesticide residues from treated land into:
- Streams
- Rivers
- Lakes
- Reservoirs
Leaching Through Soil
Some pesticide chemicals can move downward through soil and eventually reach groundwater.
The likelihood depends heavily on the chemical, soil type, geology, rainfall, and depth to groundwater.
Spray Drift
Small droplets or particles may drift away from the intended treatment area during application, particularly under inappropriate spraying conditions.
Spills and Improper Disposal
Concentrated products can contaminate soil or water if they are spilled, improperly stored, poured onto the ground, or disposed of incorrectly.
Pesticides are not primarily an ozone-layer problem. The more relevant environmental concerns include contamination of soil, groundwater and surface water, exposure of non-target organisms, and chemical-specific persistence or ecological toxicity.
How Can Pesticides Get Into Drinking Water?
Pesticides can potentially reach drinking-water sources through both surface-water and groundwater pathways.
EPA identifies applications to:
- Farmland
- Gardens
- Lawns
- Other treated areas
as possible sources from which pesticide chemicals may eventually reach water.
Surface-Water Contamination
Runoff can carry pesticide residues into rivers, lakes, and reservoirs used as drinking-water sources.
Groundwater Contamination
Some chemicals can leach through soil into groundwater.
Private wells may deserve additional attention when located near:
- Agricultural fields
- Orchards
- Golf courses
- Commercial pesticide-use areas
- Sites with a history of chemical storage or spills
Wellhead Contamination
Contamination can also occur directly around a poorly protected well through:
- Spills
- Improper pesticide mixing
- Improper storage
- Back-siphoning from application equipment
- Improper disposal
Pesticides do not normally enter household drinking water simply by “seeping through cracked water lines.” Source-water contamination, groundwater movement, runoff, spills, well construction, and improper handling are more relevant pathways.
Are Pesticides Regulated in Public Drinking Water?
Some individual pesticide-related chemicals have federal drinking-water standards.
However, “pesticides” are not regulated as one single contaminant category with one universal limit.
Different chemicals have different:
- Maximum Contaminant Levels
- Monitoring requirements
- Toxicity profiles
- Treatment considerations
If you receive public water, review your utility's annual Consumer Confidence Report for regulated contaminants detected in the system.
For a broader explanation of drinking-water standards, see our Drinking Water Contaminants Reference Guide.
How Can You Test Drinking Water for Pesticides?
Testing for pesticides is more complicated than testing for basic characteristics such as pH or hardness.
There are hundreds of pesticide active ingredients, metabolites, and degradation products, so laboratories generally test for specific groups or analytical panels.
Start With Local Risk
If you use a private well, ask:
- What pesticides are commonly used nearby?
- Is the property near agricultural land?
- Are there known contamination sites?
- Have nearby wells detected pesticide residues?
- What does the state or county recommend testing for?
Use an Appropriate Laboratory
Contact a certified drinking-water laboratory and explain why you are concerned about pesticides.
The laboratory or local health agency may recommend a test panel based on:
- Local agricultural use
- Historical land use
- Known regional contaminants
- Your well location
There is no single home test that reliably screens for every pesticide. Testing works best when the likely chemicals are identified first.
Can Water Filters Reduce Pesticides?
Some water-treatment technologies can reduce specific pesticides, but no single treatment can be assumed to remove every pesticide equally well.
Activated Carbon
Granular or block-activated carbon can adsorb many organic chemicals and is commonly used to treat selected pesticides and other organic contaminants.
Performance depends on:
- The pesticide
- Carbon type and quantity
- Contact time
- Water chemistry
- Flow rate
- Filter age
Reverse Osmosis
Reverse-osmosis systems can reduce many dissolved contaminants, including certain pesticide compounds.
Actual performance is chemical-specific and depends on membrane and system design.
Other Treatment Processes
Depending on the chemical and treatment scale, other technologies can include:
- Advanced oxidation
- Specialized adsorptive media
- Combination treatment systems
Choose treatment based on the specific pesticide identified—not on the generic word “pesticides.” A filter that performs well for one herbicide or insecticide may not provide the same reduction for another.
How Can You Reduce Pesticide Exposure at Home?
The best way to reduce pesticide exposure is often to prevent unnecessary contact in the first place.
1. Read and Follow the Product Label
Pesticide labels contain legally enforceable directions about application, protective equipment, storage, disposal, and where the product may be used.
2. Use Only the Amount Directed
Using more pesticide than the label specifies does not necessarily improve control and may increase exposure or environmental contamination.
3. Store Products Securely
Keep pesticides in their original labeled containers and store them away from children, pets, food, and drinking-water equipment.
4. Never Transfer Pesticides Into Food or Beverage Containers
Putting pesticides into bottles, cups, or food containers can create a serious poisoning hazard.
5. Protect Private Wells
Do not mix, store, or spill concentrated pesticide products near a wellhead. Maintain proper well construction and follow local setback requirements.
6. Dispose of Products Correctly
Follow the pesticide label and local household hazardous-waste guidance. Do not pour unused pesticides into drains, onto the ground, or into stormwater systems.
What About Berkey® Filters and Pesticides?
Black Berkey®-related manufacturer information includes independent laboratory testing involving pesticides and herbicides.
However, the category “pesticides” contains many chemically different compounds.
For that reason, pesticide performance should be evaluated using the test documentation for the specific filter element and specific compound rather than assuming every pesticide will behave identically.
The stainless-steel Berkey® vessel does not determine the level of contaminant reduction. Performance comes from the filter element installed inside the system.
If a particular pesticide is your primary concern, review the current filter testing and confirm that the compound itself—or an appropriate representative compound—is included before relying on the filter for that purpose.
You can review current information on our Water Filter Test Results page and compare available filter options on our Berkey® Replacement Filters page.
Should You Buy a Water Filter Just Because You Live Near Farmland?
Not necessarily.
Proximity to agricultural land can be a reason to investigate local water quality, especially for private-well households, but it does not prove that your water contains pesticide residues.
A better sequence is:
- Identify your water source.
- Review local agricultural and environmental conditions.
- Check public water-quality information or test a private well where appropriate.
- Identify the specific chemical concern.
- Select treatment with documented performance for that contaminant.
Frequently Asked Questions
Are pesticides volatile organic compounds?
Not as a general category. Some pesticide ingredients are volatile organic compounds, while many others are not. “Pesticide” describes a product's intended function rather than one chemical class.
Is arsenic a pesticide or a VOC?
Arsenic is a chemical element, not a volatile organic compound. Certain arsenic compounds were historically used in some pesticide applications, but that does not make arsenic itself a VOC.
What is an active pesticide ingredient?
An active ingredient is the component intended to prevent, destroy, repel, mitigate, or otherwise control the target pest.
Does “inert ingredient” mean harmless?
No. In pesticide regulation, an inert ingredient is simply an ingredient that is not the active pesticidal ingredient. The term does not indicate that the substance is nontoxic or risk-free.
Can pesticides contaminate drinking water?
Yes. Certain pesticides can reach surface water or groundwater through runoff, leaching, spills, improper disposal, or other pathways. Whether they are actually present in your drinking water requires monitoring or testing.
Are private wells more vulnerable to pesticides?
Private wells near agricultural or pesticide-use areas may warrant additional attention, especially if the well is shallow, poorly protected, or located in geology that allows contaminants to move easily into groundwater.
Can you taste pesticides in drinking water?
Not reliably. Some chemicals may affect taste or odor at certain concentrations, but sensory appearance cannot determine whether pesticide residues are present.
Does boiling water remove pesticides?
Boiling should not be relied upon as a general pesticide-removal method. Different pesticide chemicals behave differently with heat, and some nonvolatile substances may become more concentrated as water evaporates.
Does activated carbon remove pesticides?
Activated carbon can reduce many organic pesticide compounds, but performance is chemical-specific and depends on the filter design, media quantity, flow rate, water chemistry, and service life.
Does reverse osmosis remove pesticides?
Reverse osmosis can reduce many pesticide compounds, but performance should be confirmed for the particular chemical and system.
Do Berkey® filters reduce pesticides?
Manufacturer-published testing for Black Berkey®-related filtration includes pesticides and herbicides. Because pesticide chemistry varies widely, review contaminant-specific test documentation for the filter element you are considering rather than assuming identical performance for every pesticide.
Do organic pesticides have no health risk?
No. Naturally derived pesticides can still be toxic at sufficient doses. Risk depends on toxicity and exposure, not on whether a substance is described as natural, organic, or synthetic.
Are organophosphate pesticides banned?
Not as an entire chemical class. Regulatory status varies by specific active ingredient and approved use. Some individual products or uses have been restricted or discontinued, while others remain registered.
What should I test for if I live near agricultural land?
Ask your state environmental or health agency, county extension office, or certified laboratory which pesticides, nitrates, metals, or other contaminants are relevant to local agriculture and groundwater conditions.
Final Thoughts
Pesticides are not a single chemical or even a single chemical family.
They include many different substances used to control insects, weeds, fungi, rodents, and other pests, and their environmental behavior and toxicity vary considerably.
Some pesticide chemicals can move from treated land into surface water or groundwater, which makes them a legitimate drinking-water concern in certain locations—particularly where private wells are close to agricultural or other pesticide-use areas.
But the appropriate response is not to assume that every water source contains pesticides or that every filter treats every pesticide equally.
Start with the water source, identify the pesticide or chemical of concern, test where appropriate, and then choose a treatment method with documented performance for that specific contaminant.