Part One – Pesticides: Killing the Pest or Killing the Earth?

Did you know that approximately 2 540 117 t (or 5.6 billion pounds) of pesticides are used worldwide? Or that 1.8 billion people engage in agriculture, with a lot of them using pesticides to protect food and commercial products that they produce? (1)  Or that the global market for pesticides is expected to reach $65,3 billion in 2017? (2) Big numbers, I know.

They are also used for non-agricultural purposes. They are everywhere.

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Picture Source

What exactly are pesticides?  US Environmental Protection Agency gives us this definition:

“A pesticide is any substance or mixture of substances intended for:

  • Preventing, destroying, repelling or mitigating any pest.
  • Use as a plant regulator, defoliant, or desiccant.
  • Use as a nitrogen stabilizer“.  (3)

You can find a broader definition in FIFRA.

There are different criteria by which pesticides are classified, for example, they can be classified according to the type of pest they control; according to their stability (degradable, persistent) or whether they are chemical-related or biopesticides.

Here is a classification of pesticides according to the type of pest they control:

  • Acaricides – Kill mites that feed on plants and animals.
  • Algicides – Control algae in lakes, canals, swimming pools, water tanks, and other sites.
  • Antifouling agents – Kill or repel organisms that attach to underwater surfaces (for example: boat bottoms).
  • Antimicrobials – Kill microorganisms (such as bacteria and viruses).
  • Attractants – Attract pests (for example, to lure an insect or rodent to a trap, however, food is not considered a pesticide when used as an attractant).
  • Biopesticides – certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals.
  • Biocides – Kill microorganisms.
  • Disinfectants and sanitizers – Kill or inactivate disease-producing microorganisms on inanimate objects.
  • Fungicides – Kill fungi (including blights, mildews, molds, and rusts).
  • Fumigants – Produce gas or vapor intended to destroy pests in buildings or soil.
  • Herbicides – Kill weeds and other plants that grow where they are not wanted.
  • Insecticides – Kill insects and other arthropods.
  • Microbial pesticides – Microorganisms that kill, inhibit, or out compete pests, including insects or other microorganisms.
  • Molluscicides – Kill snails and slugs.
  • Nematicides – Kill nematodes (microscopic, worm-like organisms that feed on plant roots).
  • Ovicides – Kill eggs of insects and mites.
  • Pheromones – Biochemicals used to disrupt the mating behavior of insects.
  • Repellents – Repel pests, including insects (such as mosquitoes) and birds.
  • Rodenticides – Control mice and other rodents. (3)

The use of chemicals helped increase productivity, but caused great concern about their effect on human health and environmental safety. On the other hand, chemicals have helped us be protected against diseases that were carried by insects, especially mosquitoes. Our society has changed from an agricultural one to an industrial and finally to a communicational one, and publicity concerning the use of pesticides has never been balanced from the standpoint of the good and the bad. Basically, information about the potential adverse effects of pesticides are thrown in our faces, without reference to the good. (4)

What is good about pesticides, you ask?

mosquitos-better

Picture Source: Mosquito Magnet®

Well, for example, there are caterpillars that feed on the crop and killing them brings higher yields and better quality. Great benefits have been derived from the use of pesticides in forestry, public health, the domestic sphere and, of course, in agriculture. Vector-borne diseases are most effectively tackled by killing the vectors and insecticides are often the only practical way to control the insects that spread deadly diseases such as malaria, resulting in an estimated 5000 deaths each day. Disease control strategies are crucially important also for livestock. Insecticides protect buildings and other wooden structures from damage by termites and woodboring insects. (5)

pesticides-better

Airplane Image Source

We’ll get to the bad effects and the “Pesticide Hall of Shame” in the next post. In this one we’ll go through the history of pesticide use.

Using pesticides isn’t something new. The first recorded use of pesticides is about 4500 years ago, when the Sumerians used sulphur compounds to control insects and mites, while 3200 years ago the Chinese were using mercury and arsenical compounds for controlling body lice. Pesticides were also used by the Ancient Greeks and Romans for different purposes, such as control of plant diseases, weeds, insects and animal pests. Back in those days there was no industry, so any products used, had to be either of plant or animal derivation or, if of mineral nature, easily obtainable or available.

So, for an example, smokes were used against mildew and blights. People burned some material such as straw, chaff, fish or an animal horn to windward so that the smoke, preferably malodorous, would spread through the orchard, crop or vineyard. Various plant extracts, like bitter lupin or wild cucumber were used against insects. Crawling insects were trapped by using tar. Weeds were controlled with salt and sea water. Extract from the flower Pyrethrum daisy (Chrysanthemum cinerariaefolium) has been used for over 2000 years. (6)

In the early 1800s pyrethrum flowers were used by Caucasian tribes and in Persia to control body lice. The flowers were first produced commercially in Armenia in 1828. (7)

800px-fields_of_white_daisies_chrysanthemum_cinerariaefolium_

Picture Source: Wikipedia

Up until the 1940s inorganic substances (sodium chlorate and sulphuric acid, for example) and organic chemicals (derived from natural sources) were widely used in pest control. Organic chemicals such as nitrophenols, chlorophenols, creosote, naphthalene and petroleum oils were used as fungicides and insecticides, while ammonium sulphate and sodium arsenate (inorganic chemicals) were used as herbicides. These substances were not selective and were phytotoxic (toxic effect on plant growth). (6)

Herbicides were developed after WWII in order to increase food production and create possible warfare agents. (8) In fact, World War II served as a spring-board for the modern agricultural-chemical industry. (The chemicals and technologies initially developed for warfare during that era were later rerouted for use on farms. For example, German scientists experimenting with nerve gas during World War II synthesized the organophosphate insecticide parathion. It was first marketed in 1943, and to this day, parathion is still widely in use). (9)

Effects of DDT, BHC, aldrin, dieldrin, endrin, chlordane, parathion, captan and 2,4-D were discovered. All these are synthetic pesticides. They were inexpensive and effective. DDT was the most popular and widely used because of its broad-spectrum activity and it seemed to have low toxicity to mammals. It also helped reduce insect-born diseases, like malaria, yellow fever and typhus. However, in 1946 reports surfaced that DDT caused harm to non-target plants and animals and that there were problems with residues. (DDT was eventually banned in 2001). (6)

Nobody was concerned! There were no reports of people dying or being poisoned (except in the cases of misuse) and life went on.

Research continued, and in 1970s and 1980s, glyphosate, the low use rate sulfonylurea and imidazolinone (imi) herbicides were introduced to the world. Other new families of insecticides and fungicides were made known to the market. As many of the agrochemicals introduced at this time had a single mode of action, thus making them more selective, problems with resistance occurred and management strategies were introduced to combat this negative effect. (6)

In the mid 1980s the U.S. EPA cancelled the use of the herbicide 2,4,5-T (2,4,5-Trichlorophenoxyacetic acid) because of the dioxin contamination. Dioxins are classified as carcinogens and are also known to affect the reproductive and immune systems. (8)

In the 1990s new members of existing families which have greater selectivity and better environmental and toxicological profiles were researched. New families of agrochemicals have been introduced to the market such as the triazolopyrimidine, triketone and isoxazole herbicides, the strobilurin and azolone fungicides and chloronicotinyl, spinosyn, fiprole and diacylhydrazine insectides. Many of the new agrochemicals can be used at grams rather than the kilograms per hectare. (6)

In the 1990s a new term was introduced to the world and it was: endocrine disruptor.

What are endocrine disruptors, and how they affect us or our environment, will be explained in one of my next posts.

So, there you have it – the history of something that saves lives and harms the environment. The most important question is: How much of what? Too much of a good thing is almost never good. Too much of a bad thing is always catastrophic.

What do you think? Sound bellow, I’d love to hear your opinion!

Coming next: Pesticide Hall of Shame. Stay tuned!

References:

(1): Alavanja, Michael C.R. “Pesticides Use and Exposure Extensive Worldwide.”Reviews on environmental health 24.4 (2009): 303–309. Print. Online source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2946087/  (30.09.2016)

(2): Online source: http://www.bccresearch.com/pressroom/chm/global-market-pesticides-reach-$65.3-billion-2017 (30.09.2016)

(3): Online source: https://www.epa.gov/ingredients-used-pesticide-products/types-pesticide-ingredients (30.09.2016)

(4): Mrak EM: Pesticides: the good and the bad. Regul.Toxicol.Pharmacol. 1984; Mar;4(1):28-36. Online source: https://www.ncbi.nlm.nih.gov/pubmed/6425996 (30.09.2016)

(5): Aktar, Md. Wasim, Dwaipayan Sengupta, and Ashim Chowdhury. “Impact of Pesticides Use in Agriculture: Their Benefits and Hazards.” Interdisciplinary Toxicology 2.1 (2009): 1–12. Online source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2984095/ (30.09.2016)

(6): Online source: http://agrochemicals.iupac.org/index.php?option=com_sobi2&sobi2Task=sobi2Details&catid=3&sobi2Id=31 (30.09.2016)

(7): John E. Casida: Pyrethrum Flowers and Pyrethroid Insecticides. Environmental Health Perspectives Vol. 34, pp. 189-202, 1980. Online source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1568513/pdf/envhper00470-0186.pdf (30.09.2016)

(8): Online source: http://www.toxipedia.org/display/toxipedia/Pesticides+-+History (30.09.2016)

(9): Online source: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiygIv7lLfPAhXCxxQKHQrSBw0QFggdMAA&url=http%3A%2F%2Fwww.sref.info%2Fresources%2Fpublications%2Fpesticide-development—a-brief-look-at-the-history%2Fat_download%2Ffile&usg=AFQjCNHNSv9P6zNyJiA1pxgfVUP6qg4XBw (30.09.2016)

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