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First let’s define pest.  A pest can be almost any living thing considered by us, humans, to be undesirable; for example, insects, rats, mice and other animals, plants, fungi, bacteria, and viruses.  Even deer, when they go after your shrubs or vegetable garden, can be considered nuisance animals or pests.  The challenge of pesticide use is to maximize their effectiveness against pests while minimizing their hazards to humans, other animals, and the environment. As with most complex issues, there are bound to be tradeoffs.

OK, so what is a pesticide?

A pesticide as defined by the US Environmental Protection Agency is “Any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest.”  (See   Whether something is considered a pesticide depends on the claims made by whoever is selling it.

Many different substances have been developed for use as pesticides, some synthetic and some naturally-occurring. Pesticides can take almost any form.  Dried blood, garlic, putrescent whole egg solids, caffeine, pool chemicals and even–believe it or not–a washing machine have been regulated as pesticides.

Try this pop quiz.
Is caffeine:
1)  a drug?
2)  a natural component in food?
3)  a pesticide?

Caffeine is actually all three and chemically identical in each case.  The difference resides in the claims of manufacturers. Thus, when caffeine is sold as a product to keep you awake, it is regulated as a drug.  When drunk as part of your coffee, it’s a natural component of food.  And yes, it’s been used as a pesticide.

Years ago, Hawaii was fighting the invasion of a non-native frog that, if left unchecked, could damage its fragile ecology. Hawaii received special approval by the Environmental Protection Agency (EPA) to use caffeine as a pesticide to control the invasive frogs.

There was even a washing machine which was ruled by the EPA to be a pesticide because its manufacturer claimed it would sanitize clothes by releasing nano-silver.  Interestingly, the entire machine, not just the nano particles was viewed as a pesticide.  We may not usually think about microbes as pests, but if a product is sold to control them, the product can be a pesticide.

At home, look at the labels of the products you use to clean and sanitize your home.  If the product claims to sanitize, it’s a registered pesticide.  Among the highest volume pesticides are chemicals, such as chlorine, used to purify our water and keep our pools safe to swim in.  Thus, pesticides appear in many settings and, although designed to be hazardous to their targets, should ideally be safe to use as directed.

Is “pesticide” the same as “insecticide”?  What are other kinds of pesticides?

Insecticides are just one type of pesticide.  In fact, insecticides make up less than 2% of the pesticides used in the US.   There are many different classes of pesticides, including:

Fungicides – To control mold and other kinds of fungus
Herbicides – To kill weeds
Antimicrobials, disinfectants and sanitizers – To kill microorganisms
Algicides – To kill algae
Antifouling agents – To repel barnacles and other unwanted growths in water environments
Attractants – To attract pests; these are traps with a pesticide and food to lure pests
Insecticides – To kill insects and arthropods
Repellents – To keep away pests, for example mosquitoes, birds, deer, dogs, etc.

Are pesticides good or bad?

Pesticides are essential to our food supply, to water purification, and for sanitizing surfaces in hospitals, home and manufacturing.  They protect us from disease carrying insects and many other pests. If used according to the label, pesticides are safe for human health and the environment.  Workers in many settings can be exposed to pesticides.  Various worker safety programs help ensure their safety.  It is probably pesticide use in the food supply that is most controversial.  Safety standards have come a long way towards reducing pesticide residues in foods and prohibiting pesticides for which the risk of harm is too great.  Integrated Pest Management (IPM) is a program of controlling pests that relies on physical, cultural, biological, and chemical strategies, instead of just relying on synthetic chemicals.

If you are using a product to control pests, it’s BEST to use a pesticide registered by the US Environmental Protection Agency.

Why is this so important?

Because the EPA reviews every pesticide to ensure that it’s both effective and safe for humans and the environment.
For example, diatomaceous earth is used both as a pesticide and in food contact applications.  The label on the food grade diatomaceous earth makes it look safer than the pesticide version in fact, both present similar risks.  The difference is that the EPA requires that diatomaceous earth used for pest control have labels to tell you how to use it safely and effectively.

READ pesticide labels.  Each word on every label is approved by the EPA. They invest much effort in deciding the best ways to communicate the hazards of the products.  Their goal is to ensure the product is used both safely and effectively. Both EPA and the supplier of the product want you to be safe.  The best way to do this is to follow the instructions on the label.

In contrast, if you see a product with the disclaimer “this product is not meant to prevent, destroy, repel, or mitigate any pest,” it means the product wasn’t approved by the EPA for pest control, and the product’s safety and effectiveness in controlling pests are likely unknown.

Pesticide labels can look scary because they list all of the potential effects of the products.  However, toxicologists view these labels as a positive thing: it means the product has been tested in detail and this allows us to know safe and unsafe exposure levels.  In contrast, a product with the disclaimer mentioned above suggests little is known about the material.
Always remember also that a hazard may never pose a risk to your health:  risk always depends on your exposure to the hazard.

Are pesticides new to society?

No.  Pesticides have been used since ancient times.  Historically, pesticides were highly toxic, but the advent of the fields of toxicology and modern chemistry has resulted in far safer ones.  In addition, today the use of pesticides is tightly regulated whereas historically there was little or no regulation of their use.  Rachel Carson’s groundbreaking book, “Silent Spring”, alerted the public to the potential environmental hazards of certain pesticides, and was instrumental in giving birth to the broader global environmental movement.

For example, as early as 900 AD, the Chinese were using arsenic to control garden pests, and by the 1600s it and other chemicals were used in Western societies as pesticides as well.

Wide scale use of arsenic in agriculture began in the US in the 1860s.  Until DDT was introduced in the 1940s, lead arsenate was the top used insecticide in the US.  While from a modern perspective DDT is seen as a “bad” pesticide because of its persistence and bioaccumulation, it was remarkably safer both for humans and the environment than lead arsenate.  DDT degrades only slowly but lead arsenate never degrades. Lead arsenate was also much more acutely and chronically toxic than DDT.

For an excellent review on the historic use of pesticides, you may want to track down this article from the Bulletin of Historical Medicine (45:219-241): “Insecticide Spray Residues and Public Health: 1865-1938” by J.C. Whorton.

Today, most modern pesticides are even safer than DDT.  In addition, tight regulatory controls of pesticides ensure that they are tested for potential health effects before they are introduced to the marketplace and also that we aren’t overexposed to them.

Controlling pests by various means while balancing safety with effectiveness has been a big challenge throughout history.  It surprises many people to learn that both “organic” and conventional farms use pesticides to produce food.  Notably, in California the top used pesticide by some organic farms is the same as that used by conventional farms.  Integrated pest management is also used by both organic and conventional growers.  We encourage interested readers to look further into these related topics in the recommended pesticides resource links below.


Resources for further information:

The US EPA’s Office of Pesticide Programs (OPP) regulates the manufacture and use of all pesticides in the US and establishes maximum levels for pesticide residues in food. The EPA Web site is an excellent resource for pesticide information:
– EPA’s page on Pesticides Science ( offers some basic background on the subject
– Pest Control and Pesticide Safety for Consumers ( is a page with good non-technical links
– And for the legally inclined, EPA’s page on Laws and Regulations concerning pesticides ( offers a convenient starting point.

The National Pesticide Information Center ( ) provides a variety of objective, science-based information on pesticides and pesticide-related topics.  They also operate a toll-free number staffed by a Pesticide Specialist to handle queries from the public.

Pesticide Training for Agricultural Employees:

Mythbusting 101: Organic Farming > Conventional Agriculture. Interesting blog from Scientific American addressing four common misconceptions about organic farming and foods.

A good basic video on pesticide use:

What’s in that Pesticide?   From the University of California, this video provides tips on how to read pesticide labels and determine which product is best for which application.

What are Pesticides? (2 Parts) – and (from Organic Nation) – A balanced presentation of farming with conventional and organic pesticides. This video features a professor of plant pathology at Purdue University so naturally is focused only on certain types of pests that affect plants.

Pros and Cons of Pesticide Usage – – Developed by a high school advanced placement biology and environmental science teacher, this PowerPoint presentation does a good job of conveying the science of pesticides and some basic toxicological principles at the same time.

Related topicsBasics of Dose and Exposure, Hazard vs Risk, All Natural! All Safe? Everything is a Chemical, Genetically Modified Organisms (GMOs), TEF’s “Is It Safe?” videos in English, Spanish and Japanese (subtitled) and the related “Is it Safe? Written Primer

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