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Pesticide Dosages

When we were making the movie, A Chemical Reaction, about the anti-pesticide movement sweeping Canada and now the U.S., we often heard from the chemical companies that the dosages used in lawn care were so small (if used as directed) they couldn’t possibly be harmful to humans or the environment. Legally, we know the pesticide companies can’t make safety claims about their products. The EPA outlawed that a long time ago. No pesticide can be concluded to be absolutely safe, ever.

But what about those statements as a practical matter? With just a few ounces of active ingredient in 15 gallons of water, does the average lawn treatment pose risk?

We posed that question to Dr. Alan Greene ( for the movie, a Chemical Reaction, ( His response was simple, straight-forward and very telling:

“If you look at the amount of active ingredient in medications, it’s often measured in parts per billion. In allergy medication, for example, the amount of active ingredient in a child’s dosage is infinitesimally small. So if a dosage like that can impact a child’s breathing, of course an inhaled or ingested pesticide can have an effect. Pesticides are routinely used at much larger dosages than in medicines and if those pesticides come in contact with our children, or our pets or ourselves, there is absolutely a risk.”

To clarify this issue further, take a look at this post today from Curtis Smith, a Cooperative Extension agent in Colorado:

The finer points of pesticides

By Curtis Swift

Those of us who work with pesticides realize the dose (exposure)
determines the toxicity. As Paracelsus, the “father” of modern
toxicology (1493-1541), once wrote “the right dose differentiates a
poison from a remedy.” A great example of this are the pesticides used
to keep our plants free of insects. When these are diluted properly
they work wonders. When they are not diluted properly, poisoning to
non-target organisms to include you and I can occur. When a single
lethal dose kills this is referred to as “acute” toxicity. When a
person becomes sick or dies from exposure to small amounts of a toxin
over an extended period of time, this is known as “chronic” toxicity.

Long term exposure to toxins (chronic toxicity) can occur whenever we
consume contaminated items. For that reason alone we need to keep
toxins out of the ground water. A pesticide or other toxin spilled or
applied to soil or that drips from pesticide treated trees and shrubs
may enter the ground water or leach into the river system. When that
water is next used for irrigation that crop may be contaminated with
the toxin or its breakdown metabolites. Some toxins are absorbed by
the crop making them impossible to remove while others may be on the
surface of the fruit or vegetable you eat.

Washing the fruit or vegetable may not remove the toxin. For those
drinking or otherwise using well water, the risks of chronic poisoning
is highly likely when toxic substances leach or are flushed into the
ground water supplying that well. Flushing out a spray tank near a
domestic well is certainly to be avoided. Some of the toxins found in
domestic wells are considered possible cancer-causing substance by the
U.S. Environmental Protection Agency while many others are suspected
of causing cancer. If the substance that was applied is known you
might be able to find information on its toxicity at the EXtension
TOXicology NETwork.

Even when a pesticide is diluted and applied according to label
directions, being poisoned is still possible. Pesticides require a
specific length of time after application before the fruit or
vegetable should be consumed. This is known as the pre-harvest
interval (PHI) and is based on the time it takes for the chemical to
breakdown under normal temperature, humidity, and sunlight conditions.
The PHI varies between pesticides and the crop to which it is applied.
Sevin 4F carbaryl insecticide has a three-day PHI for broccoli but a
fourteen-day PHI when applied to Chinese cabbage. If you harvest
Chinese cabbage after only 7 days, the residue of the pesticide may
affect your health. When you harvest Chinese cabbage treated with this
insecticide within seven days, store it in the refrigerator for
another seven days and then eat it, pesticide residue may still be an
issue. The residue may not break down as fast in the refrigerator as
it does when exposed to outdoor conditions.

Pesticide labels are designed to help you avoid over-application and
food and water contamination. If you don’t have the pesticide label or
can no longer read it, you may be able to find the label with all of
its instructions at Click on Services and then
“Labels/MSDS.” MSDS is the abbreviation for Material Safety Data Sheet
and provides the chemical name of the active ingredient, its chemical
formulation and EPA registration number. All ingredients are listed
except for the items classified as are ‘trade secrets.’ The acute and
chronic oral, dermal and inhalation toxicity of the product is
provided as well as precautions and potential hazards.

The Occupational Safety and Health Administration requires the MSDS be
available to employees for potentially harmful substances handled in
the workplace under the Hazard Communication regulation. The MSDS is
also required to be made available to local fire departments and local
and state emergency planning officials undPlanning and Community Right-
to-Know Act. If you are interested in the toxicity of the products
being used in your neighborhood, ask for the MSDS sheet on that
product. If an applicator is using a product on your property he/she
most likely has the MSDS for that product in their truck.

By definition a pesticide is a toxin. Even those products considered
to be organic or biological are toxic and should be considered as
such. If you think botanical or natural pesticides are safe, wait
until you read next week’s column in the Grand Junction Free Press.


Dr. Curtis E. Swift is the area horticulture agent with the CSU
Extension. Reach him at or visit

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

Number of Entries : 1023
  • KonstantinMiller

    I think I will try to recommend this post to my friends and family, cuz it’s really helpful.

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