Sustainable Agriculture Literature Review - Boulder County

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10.2 Health Effects
Pesticides
All pesticides must be toxic or poisonous in order to kill the pests they are intended to
control, for this same reason they are potentially hazardous to humans and animals as
well as pests. Pesticide toxicity varies widely and is dependent upon a number of
factors. According to the Toxicity of Pesticides the “most important factor is the dosetime
relationship,” where the dose is the quantity of a substance that a surface, plant, or
animal is exposed to and time is how often the exposure occurs. 775
The interaction between the dose and time gives rise to two different types of toxicity:
acute and chronic toxicity. Acute toxicity refers to how poisonous a pesticide is to a
human, animal, or plant after a single short-term exposure. Acute toxicity is measured as
the amount or concentration of a toxicant required to kill 50 percent of the target in a test
population also known as lethal dose 50 (LD50). 776 Given in units of milligrams per
kilogram (mg of product per kg of test animal body weight), a higher LD50 value
indicates a lower toxicity. Chronic toxicity is the delayed poisonous effect from exposure
to a substance, generally through food, water, or air. Pesticides are rated according to
their level of toxicity (acute and chronic), so while all pesticides carry a certain level of
toxicity, the risk from toxicity to human and environmental health varies. 777 An example is
glyphosate, which according the USDA and Environmental Protection Agency (EPA) is
environmentally less adverse than other herbicides (a lower environmental impact
quotient compared to other herbicides currently used in crop production). 778
Currently, more than 800 pesticide active ingredients from a wide range of commercial
products are registered for use in agricultural operations. 779 Under certain
circumstances, residues from these active ingredients occur in treated crops at the time
of harvest or can be transported into soil and water. Due to potential health risks for
consumers, resulting from acute and/or chronic dietary exposure, maximum residue
limits (MRLs) for many pesticides have been established. 780
Pesticides can produce both short and long-term effects on human health. Long-term
effects of pesticides can include disruption of the body’s reproductive, immune,
endocrine, and nervous systems, as well as elevated cancer risks. A number of
population-based studies have shown associations between certain types of pesticides
and certain cancers. 781 Two of the most commonly applied herbicides in the U.S.,
atrazine and alachlor, are recognized as endocrine disruptors. 782
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Figure 39: Associations Between Various Classes of
Pesticide and Various Forms of Cancer 783
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