How Pesticides Influence Your Water Quality

How do you learn about pesticides and how pesticides influence your water quality?   Many local water agencies will have information  relating to local water testing results and will be able to provide information and brochures relating to toxic chemicals.   Surprisingly, a number of local agencies are listed in the “impaired” category by the Environmental Protection Agency (EPA) .  For example, in California, at least 85 water bodies are listed in this impaired category.

What Type of Pesticides can be found in Local Water Sources ?

Two types of pesticides that are very commonly used in residential uses are chlorpyrifos (Dursban) and diazinon.  These pesticides often occur in local storm water runoffs.  Unfortunately, their levels of concentration are not diminished by passing through local water treatment plants.  Often the concentrations of these chemicals is high enough to effect  fundamental organisms at the base of the food chain.

Has the EPA been able to reduce the usage levels of these chemicals?

In the year 2000, The EPA announced an agreement with some pesticide manufacturers that significantly reduced most products containing chlorpyrifos (Dursban) from sale to retail customers and most commercial uses of the chemical overall.  The EPA had discovered through research that chlorpyrifos was potentially more harmful to infants, children and women.

What pesticides remain in our environment and may cause problems?

Organophosphates are called broad-spectrum pesticides, and can compromise the nervous systems of many organisms.  They are used to kill a wide variety of pests and insects, including: ants, flees, aphids, spiders, and wasps.  They can be also highly toxic to honeybees and birds, and other insects and mammals. Some researchers have found that pesticide residues can be detected on a number of foods purchased at grocery stores.

How are Pesticides introduced into our environment?

Many pesticides are introduced into our ground water and environment by the continued use of these chemicals by residents and home gardeners as well as by pest control professionals.  They are applied around home structures, in schools and businesses as well.  Many problems with these pesticides can be traced back to the application, in excess, of these chemicals in urban settings.  Many of the excess concentrations of these chemicals take place because of the sheer volume of use and the inadvertent release into the local environment.

What disposal methods do you use if you find Chloropyripos or diazinon in your home or business?

If you discover leftover and unwanted chemicals in your home, do not pour them down any drain in or around your residence.  Also please do not dispose of these chemicals in the trash.  Instead please find a local hazardous waste facility and take them to that location.  For a reference on these locations, you can telephone 1-800-CLEANUP.ORG.

Any suggestions  for proper practices for improving the health of our rivers, creeks, streams and bays?

Attempt to implement alternative strategies for your garden and try control methods that do not involve chemicals or pesticides.  This can be done by following suggestions and natural treatments that can be found in  the publication,  Our Water, One World fact sheets.  Controlling pests can be accomplished in a variety of ways.  One way is to introduce pest predators in your environment.  Oils and soaps and other biological controls can be used as well.   Some alternative pesticides are available.

Make the effort to investigate harmful chemicals and pesticides

If you are responsible for a home garden, lawn and other plants in the environment,  take a look at how pesticides influence your water quality. Read up on alternative methods for pest control and learn how to minimize the use of chemical pesticides for insect control.  Check with your local water agency and find out what testing, if any, has been done on your local water sources.  If these tests reveal high residues, get involved in your local community to suggest programs that might mitigate and reduce these chemical concentrations.

How does the Federal Government define concentrations & exposure levels of pesticides?

The Safe Drinking Water Act  (SDWA)  requires that the  EPA establish Maximum Contaminate Levels (MCL)  to insure that human health is protected.  MCL is the highest level of concentration that is allowed in public water supplies.   The MCL makes certain assumptions: that the person lives 70 years, and weighs 70 kilograms, and drinks up to two contaminated quarts of water per day.  MCL’s are subject to change, but are legally enforceable limits which must not be exceeded.

How will you know about the concentrations of pesticides in your water supply and will you be notified?

At present, public water utilities are required by the SWDA  to measure levels of contaminates in the water. They are required to collect at least four samples of tap water for analysis of any possible contamination.   If the annual average contamination of these collected samples exceeds the MCL , consumers must be notified.  If these levels are excessive, the water utility must mitigate the problem by providing an alternate water source, or blend the current water source with clean water from a non-contaminated source.

What levels are acceptable  and who is testing?

Contamination of water by these agents is measured in parts per billion (ppb).   Working to insure that the proper levels are addressed is the State Management Plan, which is overseen by the EPA.  It defines the responsibilities of state agencies with regard to standards.

How may types of pesticides are in or have been in the marketplace?

More than 50,000 pesticides have been registered with the US government since the FIFRA was enacted in the 1947.   This act was amended in 1988 and required that all pesticides in use before 1984 would be subject to evaluation by the EPA.  This act made it necessary to re-evaluate 1150 active ingredients in 45,000 formulations of products. The active ingredients were assigned into 612 chemical groups. These were further subdivided into groups called  A,B,C and D  based on the negative effects that these agents would have on food, water and human health.




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  1. Wow i love it, I am bookmarking this post and i will be sharing this on Facebook in the future with my friends, because anything that enlightens people about the dangers of pesticides in water, which as you point out can be very dangerous, when too much of the wrong type of chemical gets into the water supply.

    As some who has many friends in Agriculture i know the problems that we face here.

    Have you heard of Codex Alimentarius before? Some pretty crazy information in relation to chemicals in our water and food.

    • Hi Marley- Thanks for reviewing my post on pesticides in water & some of the dangers they pose and for passing the info along to your friends. Thanks for the the reference on the Codex Alimentarius. I was somewhat familiar with parts of it, but reviewed it further after your comments. I appreciate your interest in food safety issues.



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