All chemical pesticides are harmful to you and the environment on some level. Of course, some are worse than others, but none are completely safe. The etymology of “-cide” roots back to Latin, essentially meaning “to kill,” and while herbicides, insecticides, and indeed all pesticides are designed to kill targeted pests and problems, unfortunately, it is much, much more than those specific targets are affected by their ingredients.

The worst pesticides include Atrazine, Flupyradifurone, Hexachlorobenzene, Glyphosate, Methomyl, and Rotenone. Based on WHO data, they are particular hazards b/c of: (1) bioaccumulation; (2) persistence in water, soil/ sediment; (3) toxicity to aquatic organisms; and (4) toxicity to bees/ ecosystem services.

This article will look at the organizations that determine pesticide toxicity and provide links to current and comprehensive pesticide listings. Additionally, over 150 hazardous pesticides for the environment are named, with a brief discussion about some common pesticide ingredients in use today and the hazards associated with them.

The WHO Recommended Classification of Pesticides by Hazard

The World Health Organization (WHO) and the United Nations Food and Agriculture Organization (FAO) come together every two years for a Joint Meeting on Pesticide Management (JMPM) to readdress the toxicity of pesticides. 

The most current revision of the WHO Recommended Classification of Pesticides by Hazards was issued in 2019. Each publication also provides the current guidelines used for classification.

By the WHO’s own admission, the recommended classifications are based on incomplete, ongoing, or inconsistent data. With more garbled jargon in between, their publication states that “any classification based on biological data can never be treated as final…Reappraisal might be necessary from time to time.” Additionally, it is asserted that “any guide should supplement–but not substitute–for specialty knowledge and expertise.“

There are four official toxicity categories for pesticides as determined by the EPA: 

• I: Highly toxic–signal word: DANGER   
• II: Moderately toxic–signal word: WARNING
• III: Slightly toxic–signal word: CAUTION
• IV: Relatively or practically non-toxic–signal word: CAUTION (optional)

Notice, even the non-toxic category has significant qualifiers attached–relatively or practically.  Many of the studies behind regulations and control policies are concluded in mere months and are incapable of offering long-term data for consideration. For decades now, science has been uncovering this data and submitting the evidence for further review of culprit chemicals; however, much damage has already been done, and change is slow to take place.

The important takeaway is that you cannot be truly certain the extent to which you are harming the environment–or yourself–by using certain pesticides. Safety guidelines and regulations are provided for each chemical by the WHO, but remember that they are based on the classification subject to change–potentially frequently–in years to come.

For example, in 2009, the pesticides paraquat dichloride and endosulfan were not rated “Extremely hazardous’ nor ‘Highly hazardous’ based on the oral acute toxicity to rats. However, this presented a gross underestimation of the hazard to people, and it was later discovered that these pesticides had the highest documented human fatality rates. 

PAN International List of Highly Hazardous Pesticides (HHPs)

The Pesticide Action Network (PAN) was founded in 1982 and described themselves as “the civil society organization most steadily and continuously calling for effective international action on the elimination of hazardous pesticides.” For decades they have worked to improve policies surrounding pesticide and crop protection to make them “safer, socially just, environmentally sustainable, and economically viable pest management systems.”

While that is all well and good, keep in mind that this organization is not actually out to eliminate these harmful pesticides. Rather they are out to improve the safety policies surrounding them. They pose as a group that is concerned for the environment and your health, and while that may not be entirely untrue, they are not working to discard these hazards altogether. (An astute civilian will take note of the organizations with which PAN cooperates.)

Nonetheless, PAN “does our homework for us” by offering a list of highly hazardous pesticides (HHPs) that are extracted from the comprehensive WHO Recommended Classification of Pesticides by Hazard publication. The PAN HHP list comprises pesticides listed in the WHO Class la (Extremely hazardous) and lb (Highly hazardous).

View the complete March 2019 PAN International List of Highly Hazardous Pesticides.

145 Classified ‘Environmentally Hazardous’ Pesticides

Below is the list of all pesticides from the PAN International list of HHPs that are toxic for the environment. Superscripts given correlate to their specific classifications, as described in the legend below. 

Note: New active ingredients are steadily entering into the market prior to a JMPM review and ultimate classification by the WHO and FAO. As a result, many become available without a label identifying it as hazardous. Therefore, if you don’t find a certain chemical on this list, do not interpret that to mean it is non-hazardous to the environment.

Some of the Worst Pesticides Making Headlines

Atrazine

While this was a popular herbicide worldwide for quite some time, the EU banned atrazine in 2004. Later, the EPA “re-evaluated” it and approved it for use in 2009, noting its ability to ‘break down quickly’ in soil. However, PAN analysis using data from the United States Department of Agriculture determined that atrazine can be found in almost 90% of America’s drinking water; and such figures imply that there is not much ‘break-down’ happening at all.

Atrazine is known to alter hormones, affect the immune system, and is even linked to some congenital disabilities. This is true for humans, though we see similar effects on wildlife. For example, water that has been contaminated will harm fish and amphibians by compromising their growth, weight, immune function, and behavior. 

Perhaps the most significant proof of its detriment to the environment, studies have found that atrazine laced water was responsible for 10% of male frogs exposed turning female. And that particular study had used controlled contamination of 2.5 ppb (parts per billion), which is less than the EPA limit for drinking water in the United States.

If you’re interested in learning more about this adverse effect this chemical is having on the environment, you can read more theory here in this Berkeley News article.

Flupyradifurone

The US EPA registered flupyradifurone as a new insecticide in 2015 with claims that it is “safer for bees” than organophosphates, neonicotinoids, pyrethroids, and other previously-established insecticides. 

However, some noticed that flupyradifurone is chemically similar to neonicotinoids. Many suspected it possessed many of the same unwanted attributes as neonicotinoids and the other conventional choices, despite the safety claims. And a 2019 study of lethal and sublethal synergistic effects of flupyradifurone on honeybees determined just that.

Hexachlorobenzene

This organochlorine fungicide was widely popular for many decades, used mostly as a protectant for grain, wheat, and other field crop seeds. Hexachlorobenzene (HBC) has not been produced in the United States as a commercial product for quite some time; however, since the 1970s, most HBCs are formed as a byproduct of producing chlorinated solvents and compounds and other pesticides. 

HBCs have an incredibly high resistance to breakdown–both chemical and biological–and have contaminated all parts of our environments. HBCs have been detected in the air, water, and soil. Plants, aquatic life, mammals, and people have tested positive for HBC contamination, with humans being exposed to it mostly through the food chain.

The HBC Biomonitoring Summary from the Centers for Disease Control and Prevention (CDC) cites specific data from many government agencies and environmental organizations considered when classifying HBC toxicity. But don’t let all those acronyms, dates, and data detract you from what they’re trying to pass off as anecdotal; the fact is that HBCs are harmful.

Glyphosate

Perhaps you are already familiar with this particular organophosphate, as it is the active ingredient in Roundup, Monsanto’s popular pesticide, which has been making legal/ medical news in recent years. Glyphosate is no longer under patent with the company, and now it is used as an active ingredient in many similar products available today. 

Studies from over two decades ago determined that glyphosate is relatively non-toxic to most plants and animals. However, the herbicide is considered moderately toxic and requires the signal word WARNING to be printed on the label due to the significant irritation it can cause in the eyes.

But these studies (which made observations not exceeding two years in time) did not consider the long-term effects, which we have since seen. Over time, through constant exposure, we have now seen many hazards present themselves.

Glyphosate has become suspect for the cause of widespread kidney disease in farmers in Sri Lanka, India, and Central America. It has been banned for use in many countries, with more to follow and still consider. However, it is still commonly used in the United States. 

Additionally, glyphosate is commonly combined with other toxic herbicides such as atrazine and neonicotinoids. This is one reason why most of our food supply is contaminated with multiple pesticides when glyphosate is found. 

And it is these chemical combinations that are dangerous and highly hazardous to all life on the planet. According to the USDA, more than 225 different pesticides have been found on many commonly consumed fruits, vegetables, and grains in the United States.

Glyphosate itself is found in trace amounts in hundreds of the most common foods, including popular brand name granola bars, hummus, orange juice, and more. But even trace amounts add up, and when done multiple times daily, the effects start to take hold that much quicker. 

Methomyl

Methomyl is a neurotic insecticide, meaning it can have a poisonous effect on nerve cells or tissue. Its carbamate class is very much like organophosphates. The EPA recently determined methomyl is presumed to be hazardous to more than 1,100 endangered species, including San Joaquin kit foxes, whooping cranes, and all protected species of salmon. 

Studies from Cornell and company have shown methomyl to be highly toxic to birds, bees, fish, and other aquatic invertebrates. It can also contaminate groundwater, and plants will take up methomyl through its roots and leave traces in food.

On October 23, 2020, the EPA posted the proposed interim decisions on the registration review for methomyl and supporting and related material, including an addendum to the draft human health risk assessment. Comments are being accepted until Dec 22 if you wish to voice your opinion on methomyl’s continued use. All this information can be found by visiting regulations.gov or click here to access these specific documents and other related material.

Rotenone

Think going organic will eliminate hazards? Think again. Despite advocates for the industry claiming it has been taken off the market, this highly toxic chemical is used by organic farmers (most often unknowingly) as it is combined with pyrethrins in many products. Although it is a natural chemical, it has high toxicity that comes with nasty consequences to both you and the environment. 

Even PAN chose to overlook this deadly chemical that enhances the onset of Parkinson’s Disease and kills bees. (But as we know, these organizations aren’t looking to eliminate the problem, just document and control it.)

A tiny amount of rotenone can kill every fish in your pond, yet it continues to be approved for commercial use. Worse yet, organic food does not get tested for (natural) chemical residue, so health risks cannot be properly assessed.

Latest Changes to the PAN International List of Highly Hazardous Pesticides (HHPs)

The current revision (and continual work-in-progress) was published in February 2019. Compared to the previous version in March 2018, no changes in criteria for identifying HHPs were made; however, we saw four pesticides removed as they are no longer classified as “probable carcinogen to humans” according to the Annual Cancer Report out by the US EPA. Those four pesticides are:

• Cyflufenamid
• Sedaxane
• Sodium diethyldithiocarbamate
• Nitrapyrin

Nine pesticides were added since March 2018:

• Cyproconazole–now a presumed human reproductive toxicant
• Propiconazole–now presumed human reproductive toxicant 
• Tioxafen–now considered a probable carcinogen 
• Propineb–now considered a probable carcinogen
• Flupyradifurone–highly toxic to honey bees (oral LD50)
• Noviflumuron–now considered a probable carcinogen 
• Calcium cyanide–now classified as WHO Ia
• Sodium cyanide–now classified as WHO Ib
• Hydrogen cyanide–now classified as ‘Fatal if inhaled’ 

As you can see, flupyradifurone is the only pesticide with an environmental hazard associated with it to be added, as the rest pose a more prominent (known) danger to humans.

However, the group “Glyphosate and its salts” was also added to this list, which consists of the following six ingredients (which also are hazardous for the environment):

• Glyphosate (acid)
• Glyphosate-diammonium
• Glyphosate-isopropylamine (also known as glyphosate–isopropyl ammonium; -IPA)
• Glyphosate-monoammonium
• Glyphosate-sodium
• Glyphosate-trimesium

In addition, the 2019 revision includes an update in the classification of metaflumizone–a semicarbazone insecticide intended for veterinary treatment of fleas and ticks–as it has been observed to be “very persistent in the water-sediment environment.”

Final Thoughts

While the World Health Organization and others work to identify the worst pesticides for the environment, the process is constantly ongoing and never fully accurate. Nonetheless, these compilations are the living guides to our knowledge of ingredient toxicity. Despite these documents, however, many harmful pesticides still remain in heavy use today, so you may wish to consider going beyond safety guidelines to protect yourself when using these chemicals.  

Stay impactful,

Sources

• World Health Organization
• Food and Agriculture Organization of the United Nations  
• WHO: Public Health Impact of Chemicals for Web
• WHO: The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 2019 
• Pan International 
• PAN North America: Environmental Impacts 
• PAN International List of Highly Hazardous Pesticides March 2019 
• Science Direct: Atrazine Toxicity on Hydromineral Balance of Fish, Tilapia mossambicus 
• NCBI: PSAS: Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis) 
• EPA: Chemical Contaminant Rules 
• US EPA: Pesticides  
• Wiley Online Library: Flupyradifurone: a brief profile of a new butenolide insecticide
• Pesticide Research Institute: Flupyradifurone: A New Insecticide or Just Another Neonicotinoid? 
• Royal Society Publishing: Lethal and sublethal synergistic effects of a new systemic pesticide, flupyradifurone (Sivanto®), on honeybees 
• CDC : Hexachlorobenzene Biomonitoring Summary 
• AACR Journals: Environmental Exposure to Hexachlorobenzene (HCB) and Risk of Female Breast Cancer in Connecticut 
• U.S. Right to Know: Roundup cancer trials still a threat to Bayer, but settlement talks progressing 
• USDA Pesticide Data Program: Annual Summary Calendar Year 2018 
• PubChem: Methomyl (Compound) 
• Science Direct: Methomyl-an overview 
• Cornell Cooperative Extension Pesticide Management Education Program: Methomyl 
• Biological Diversity: EPA Reapproves Dozens of Ultra-toxic Pesticides 
• Regulations.gov: Methomyl Registration Review 
• Journals: PLOS: Progression of Parkinson’s Disease Pathology Is Reproduced by Intragastric Administration of Rotenone in Mice 
• Wayback Machine: Organic-Approved Pesticides Minimizing Risks to Bees