Pesticides and Water Quality


In modern agriculture, almost everything is grown with the help of pesticides. When these chemicals are sprayed on nearly everything we eat, we must ask: can they harm us?

Rachel Carson's book Silent Spring put the toxic and damaging effects of Dichloro-diphenyltrichloroethane (DDT) on the map in 1962, inciting a global conversation about the environmental and public health dangers of widespread pesticide use. 

The word “pesticides” refers to chemicals used to kill or deter pests. Different pesticides are used on different pests: herbicides for weeds and insecticides for insects, for example. Though some older, harmful pesticides (like DDT) are now banned, over 1,000 pesticides are still used globally, each with its own properties and human health effects.

So they kill weeds and pests, but what about humans? We help break down how pesticides can get in water and what their impacts could be on your health.

How Do Pesticides Get Into the Water Supply?

One of the primary ways that pesticides work their way into the water supply is by seeping through the soil to the groundwater. Around 50 percent of people in the US — and about 95 percent of those living in agricultural areas — rely on groundwater for drinking water.

Pesticides are most widely used in agricultural areas, so concentrations of pesticides are usually higher in those regions. Once in the environment, however, pesticides can easily spread, ending up in water through many paths: precipitation, leaching, runoff, and wind, for example.

This process can take years for chemicals to work their way through soil to the groundwater, creating a time lag between pesticide use and appearance in deeper water reserves. Once there, chemicals can stay in groundwater for decades, even if efforts are made to reduce pesticide use above ground.

Changing Pesticides, Changing Risk

Protecting crops and increasing yields has been a goal for decades now. Chemicals have been used to achieve that goal for as long, but the kinds of chemical used have changed.

Before the 1940s, compounds that included arsenic, mercury, or lead were common. Though these chemicals pose serious threats to human health, they are not very soluble, so they turned up in food more often than in water.

After World War II, pesticides shifted towards synthetic organic compounds, which were thought to be safer. These compounds, including chlorinated hydrocarbons such as DDT, are more attractedto soil than water, and so they tend to accumulate in soil and food chains as opposed to water.

When the toxic health effects of these chlorinated hydrocarbons were discovered, an effort began to replace them with safer, less toxic chemicals. One group of these new pesticides are called carbamates, and they are highly soluble in water.

Thus, while pesticides may be trending safer, they may also appear more frequently in our water sources. Long-term studies are still underway to figure out what the health effects are, but in the meantime, scientists are finding carbamates and their transformation products in our drinking water.

Environmental Protection Agency (or EPA) has health standards for pesticides before being released into the environment, but environmental groups have repeatedly identified chemicals (e.g. chlorpyrifos) that pass EPA’s requirements mark but are later found to be toxic.

What Are the Risks to Human Health?

The effects of pesticides on the human body are as varied as the chemicals themselves. Organophosphates and carbamates, for example, affect the nervous system, while others irritate the eyes or skin. They can be carcinogenic or disrupt the body’s endocrine system.

Scientists are studying both the acute and chronic effects of ingesting pesticides. Pesticides are being detected at low concentrations, and as such, acute toxic effects (like nausea or chemical burns) are of less concern for most people. Farmworkers and landscapers directly applying herbicides and pesticides are likely most at risk (consider the evolving case of glyphosate).

Many are concerned, though, that these chemicals can accumulate over time, leading to greater health effects.

Are Pesticides in My Drinking Water?

Only small quantities of pesticides have shown up in treated drinking water. There are two directions of research, however, that promise to illuminate more about how pesticides impact drinking water: 1) cumulative exposures and 2) transformation products.

So far we have been writing about one chemical at a time. In reality, there are multiple herbicides and insecticides present in the environment. Health impacts of cumulative exposure to these compounds are not well understood, which means that our general assessments of risk are likely under-estimating the potential health impacts of pesticide exposures.

As we noted above, scientists have found the transformation products of pesticides in drinking water. A pesticide transformation product is a new chemical formed when the “parent” compound (e.g. DDT) reacts under different conditions – e.g. sunlight or bacteria in the environment or UV treatment in a water treatment facility. Sometimes, these transformation products are even moretoxic than the parent compound. Until engineers and scientists identify the multiple transformation products formed when chemicals enter our treatment systems, we can’t be sure that we are adequately treating our water.

Check out our water testing packages to make an informed decision about your drinking water or get in touch with us here for more information!


Glyphosate: Most Common Herbicide Puts Tap Water at Risk

Read our quick guide on what you need to know about glyphosate (aka Roundup) and tap water.


Have you ever wondered how the food production industry has been able to keep up with feeding our world’s rapidly growing population? Or perhaps, what your food goes through before it lands on the shelf at the grocery store? The answer to both questions, in part, involves Glyphosate. Glyphosate, more commonly known as “Roundup”, is an herbicide created by Monsanto.

The discovery of glyphosate in 1973 transformed Monsanto’s operations and the global food industry. As the first non-selective herbicide invented, glyphosate can kill any weed in its path, unlike previous herbicides that could only kill specific weeds. Put into production and first commercialized in Malaysia and the UK in 1974, Roundup subsequently became the most widely used agricultural chemical in history. A shocking 9.4 million tons of glyphosate have been sprayed onto fields worldwide since 1974.

The use of Roundup has been under extreme scrutiny recently. There are around 2400 lawsuits and counting against Monsanto, claiming that glyphosate causes cancer. The first case is scheduled to start in June.

We, at SimpleWater, have created a quick guide on understanding exposure to glyphosate through drinking water: how can glyphosate end up in your water, and is glyphosate harmful to humans?

How does glyphosate end up in drinking water?

Several studies suggest that glyphosate, despite its affinity for soil, can make its way into aquatic environments and drinking water wells. Once glyphosate enters water, it becomes stable and does not degrade easily. As a result, glyphosate can enter surface and subsurface water through two main pathways:

  • Roundup windblown into bodies of water adjacent to sprayed fields
  • Irrigation runoff from sprayed fields into distant bodies of water

Humans are most likely to be exposed to glyphosate through direct inhalation and skin contact, crops treated with Roundup, or drinking water contaminated with it.

Of the 2400 lawsuits underway, most people had direct contact with Roundup by using it to spray their homes, schools, and farms. However, one drinking water facility in Florida and two in Louisiana reported glyphosate levels (9.00 parts per billion (ppb), 8.35 & 5.05 ppb respectively) above the Environmental Working Group’s health recommendation of 5ppb. 5 ppb is a much more stringent health goal than the Federal EPA’s legally enforced Maximum Contaminant Level (MCL) of 700 ppb (or 0.7mg/L).

The EWG did not flag Florida and Louisiana for water quality violations. Rather, these results were highlighted because their facilities reported concentrations above the World Health Organization and EPA’s definition of “acceptable risk” for carcinogens–a one-in-a-million chance of developing cancer.

These two facilities serve around 8600 people, all of whom could now potentially have a higher risk of developing cancer than the general population.

What does glyphosate mean for your health?

Glyphosate is classified as a Group 2A chemical by the International Agency for Research on Cancer (IARC), meaning that it is “probably carcinogenic to humans”. The IARC came to this conclusion after many studies conducted on rats in combination with human evidence from accidental exposure. The little data that does exist on humans shows an association for non-Hodgkin lymphoma, and there is sufficient evidence of carcinogenicity in animals.

Glyphosate is also associated with endocrine disruption, harm to fetal growth, and damage to kidneys and the gastrointestinal tract.

Despite the evidence from the IARC for the carcinogenicity of glyphosate, Monsanto still claims that Roundup is safe and will not cause cancer. Monsanto’s studies, however, were conducted or commissioned by pesticide companies in support of Monsanto’s goals and are kept hidden from the public.

How can you protect yourself against glyphosate?

Perhaps the lawsuits against Monsanto will be successful and Roundup will eventually come off the market, but in the meantime, SimpleWater recommends that you protect your water to protect yourself.

The best ways to protect your health and water are:

  • Do not use glyphosate-based herbicides (especially if you are on well water)
  • If you do use herbicides of any kind, do not overuse them in order to avoid run-off
  • Try to limit consumption of crops likely sprayed with glyphosate (unfortunately, this means most non-organic foods)

While the risk of glyphosate in your tap water is likely low if your water is treated by a municipality, well water owners near lawns, gardens, and farms that use herbicides may want to test their water for glyphosate. Tap Score offers a glyphosate test to add-on to any of our essential or advanced water testing kits.

For more information about other water quality issues, take a look at our blog, Tips For Taps, or email us at!