Pesticides

What Are Pesticides?

These are chemical compounds used to kill pests, including insects, rodents, worms, weeds, and fungi. There are many classes of pesticides, including:

  • Organophosphates (e.g. parathion, chlorpyrifos [trade name Dursban])
  • Carbamates (e.g. aldicarb, carbaryl)
  • Pyrethrins/pyrethroids (pyrethrin, deltamethrin)
  • Chlorinated hydrocarbons (e.g. DDT, lindane [trade name Kwell])
  • Organometallic pesticides (e.g. various arsenic and mercury compounds)
  • Nitrophenols (e.g. 2,4-dinitrophenol)
  • Herbicides (e.g. diquat, paraquat)

Over 1 billion pounds of pesticides are used each year in the U.S. alone as well as over 4 billion pounds worldwide.3

How Can My Child be Exposed to Pesticides?

Pesticides are widely used for many purposes, including home, garden, commercial, and agricultural pest control. Thus, the potential for some degree of exposure to these chemicals is great. In general, pesticides can enter the body through the lungs, the mouth, and the skin. Of course, each class of pesticide will differ somewhat in the specific way it is absorbed. Recent studies have shown that young children may be at particularly increased risk of pesticide exposure for several reasons:12

  • their tendency to explore their environment with their mouths
  • their closeness to the ground
  • their increased time playing outdoors.

Kids may be exposed to pesticides in the following ways:

In food:5

  • The diet is clearly an important potential route of pesticides exposure in children and adults.
  • The small amounts of pesticides present on our food are called pesticide residues. Both adults and children consume these residues regularly to some degree.
  • Children’s diets are relatively higher in fruits and vegetables than adults. Thus, they may be at increased risk of exposure from their diet.
  • According to the National Research Council, differences in diet between children and adults are responsible for most of the differences in the possible health effects of pesticides.
  • Children and infants tend to eat fewer types of foods and eat more processed foods than adults (infant formula, baby food, etc.). There is very little current evidence about the amount of pesticide residues in processed foods. However, the limited available evidence shows that processed foods in general may actually have fewer residues than unprocessed foods.

In the home:

  • It is estimated that over 90% of U.S. homes use some form of pesticide.3
  • In fact, most toxic pesticide exposure in humans occurs from misuse or accidents in the setting of the home or garden. 3
  • Infants may be exposed to pesticides in household dust by skin contact, breathing, and eating of the dust.6
  • One study has found that pesticide residues may remain on toys, pillows, and other surfaces for up to 2 weeks after the house has been sprayed for bugs. 9

In drinking water:

  • Since children consume more water than any other substance, the water supply is clearly an important possible route of exposure to environmental chemicals.
  • Several scientific studies have examined the relative amounts of various pesticides in the drinking water supply in different parts of the country. Except in a few areas where dramatic pesticide contamination has occurred, most studies have concluded that the levels of pesticide in the drinking water supply in the U.S. is extremely low. 8

Outside the home:

  • This category would include school, playground, daycare, and commercial settings.
  • These settings are probably not as important as the home in terms of pesticide exposure to children.6   However, exposure is possible in these settings especially if there has been recent pesticide application.

In agricultural settings:

  • Agricultural settings may be a risk factor for pesticide exposure in children, especially when one or both parents are agricultural workers. 11
  • Children may be exposed while playing in fields sprayed with agricultural pesticides.11
  • Also, pesticide residues may be tracked into the home by parents who are agricultural workers.11
  • One study looked at specific activities that might increase the chances of exposure to children of agricultural workers. These include: 10, 11
    • a delay in changing clothing after spraying pesticides
    • mixing pesticide-contaminated clothing with the family wash
    • applying pesticides within 50 yards of the well
  • It is important to remember that some of the pesticides used in agriculture may still remain on the fruits and vegetables in the supermarket.
  • Also, we may be exposed to pesticides in agricultural products imported from developing countries.

What are the health effects of pesticide exposure?

The health effects from pesticide exposure will depend on the type of pesticide involved and the level of exposure. The health effects of each major class of pesticide considered to be important in children’s environmental health will be discussed in terms of two types of exposure: acute, high-level exposure and chronic, low-level exposure.

1. Organophosphates and Carbamates:

These two classes of pesticides share a similar way of causing health problems. However, the organophosphates are generally much more toxic than the carbamates.

Acute, high level exposure:

Immediate effects -- Such exposure may produce the following findings in minutes to hours: 1

  • heart rate changes (increased or decreased)
  • pinpoint pupils
  • increased tear formation in the eyes
  • nausea/vomiting
  • diarrhea
  • muscle cramps
  • difficulty breathing
  • emotional instability
  • confusion
  • slurred speech
  • seizures
  • coma
  • possibly death

Delayed effects -- Some studies have shown that repeated high-level exposures can cause the following problems from days to months after exposure:

  • Damage to nerves in arms and legs18, 27
  • Muscle weakness18, 27

Chronic, low level exposure:

  • There is limited evidence showing that these levels of exposure cause health problems in humans.20, 23, 24, 38, 43, 44
  • However, several animal studies have given us reason for concern, especially since these chemicals are so widely used. These studies have suggested that certain pesticides may cause problems with brain development. 13, 25, 26
  • One animal study has shown that even a single low dose of organophosphate pesticide given during a vulnerable window of time during development may produce permanent changes in brain chemistry and behavior. 13

How do I know if my child has been exposed to an organophosphate pesticide?

  • There is a medical test available that can estimate the amount of organophosphate a child may have been exposed to. It involves the measurement of an enzyme in the blood called cholinesterase.
  • If you are concerned that your child may be acutely poisoned, immediately call 911 and seek emergency assistance.

2. Organochlorines:

  • DDT, perhaps the best-known organochlorine, was banned from use in the U.S. in 1987 because of its negative effects on wildlife and its tendency to persist for long periods of time in the environment.
  • One of the few remaining pesticides in this class still in use is lindane (Kwell), which is used as one option for the treatment of head lice.
  • Though these chemicals are no longer widely used in the U.S, they may still be frequently used in other parts of the world, especially in developing countries.49

Acute, high-level exposure:

This health effects of this type of exposure has been studied from several individual case studies. These health effects may not be representative of whole populations. Based upon this limited evidence, such exposure to organochlorine pesticides may produce:

  • problems with blood clotting46
  • severe confusion48
  • seizures45
  • possibly death47

Chronic, low level exposure:

  • There is limited human evidence demonstrating long-term health effects of low dose, chronic exposure to organochlorines.34, 35, 36
  • There has been some concern that exposure to organochlorines is associated with increased risk of breast cancer and endometrial cancer, but the weight of the available evidence argues against these associations.30, 31, 32, 33, 37
  • Several animal studies have given us reason for concern that organochlorines may cause problems with brain development. These studies have demonstrated permanent changes in brain chemistry and behavior when animals were given low doses of these chemicals in vulnerable times during development.14, 52

3. Pyrethrins/Pyrethroids:

  • These pesticides are a family of compounds either directly derived from a species of the chrysanthemum plant (pyrethrins) or manufactured to resemble these chemicals (pyrethroids).
  • In general, these compounds are considered relatively safe to humans because of their low toxicity compared with other classes of pesticides.
  • One common use of pyrethrins today is as a less toxic alternative to lindane for the treatment of head lice.
  • The pyrethroids are considered to be less toxic than the pyrethrins and are being increasingly used for some agricultural crops.

Acute high-level exposure:

This type of exposure to pyrethrins may cause [1]:

  • allergic sensitization
  • contact skin irritation
  • itch
  • runny nose
  • asthma symptoms (wheezing, cough, shortness of breath)

Acute high-level exposure to pyrethroids may cause temporary painful sensations known as parasthesias.19, 40, 41 However, none of the other health effects listed above have been consistently associated with the pyrethroids.

Chronic low-level exposure:

  • There is little human evidence that pyrethrins or pyrethroids cause health problems with this type of exposure.28, 42
  • However, several animal studies have given us reason for concern, especially given the widespread use of these chemicals. Some of these studies have shown that exposure to low doses of these compounds, even in a single dose, may cause permanent changes in brain chemistry and behavior.15, 16
  • A few animal studies have linked various pyrethrins and pyrethroids with increases in certain forms of cancer, but the evidence is not overwhelming. 17, 24

How can I reduce pesticide exposure to my child?

  • If you learn that a particular shipment of fruits or vegetables is heavily contaminated with pesticides, don’t let your child eat this produce.
  • If your child needs to be treated for head lice, follow the treatment directions exactly and use no more than you absolutely need.
  • Try to reduce pesticide use in the yard by growing plants that naturally grow well in your area.2
  • Consider pulling weeds by hand in your yard or garden rather than using chemical weed killers.
  • When you have your home sprayed for insects, keep your children’s blankets, pillows, and stuffed animals covered and stored outside.9
  • If your work involves the use of pesticides, change from your work clothes before coming home. Also, wash these work clothes separately from the family wash.11
  • If you have a well, do not apply any pesticides within 50 yards of it.11
  • Do not store pesticides within easy reach of children in the home.11

October 2008

References

References

[1] Ellenhorn's Medical Toxicology, 2nd Edition. Pesticides. Williams & Wilkins 1997: 1614-1663.

[2] Etzel R, Balk, S. Handbook of Pediatric Environmental Health. American Academy of Pediatrics Committee on Environmental Health Affairs, 1999: 193-212.

[3] Schenker M, Louie S, et al. Environmental and Occupational Medicine, Third Edition. Pesticides. Lippincott-Raven Publishers 1998;83:1157-70.

[4] Schettler T, Stein J, et al. In Harm’s Way:Toxic Threats to Child Development. Greater Boston Physicians for Social Responsibility 2000: 80-85.

[5] Landrigan P, Mattison D, et al. Pesticides in the Diets of Infants and Children. National Research Council, Committee on Pesticides in the Diets of Infants and Children 1993; 1:13-23; 2:25-36; 5:159-193.

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[24] U.S. EPA Office of Pesticide Programs Tracking Report. February 19,1997.

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[30] Romieu I, Hernandez-Avila M, et al. Breast cancer, lactation history, and serum organochlorines. American Journal of Epidemiology 2000;152(4):363-70.

[31] Sturgeon S, Brock J, et al. Serum concentrations of organochlorine compounds and endometrial cancer risk (United States). Cancer Causes & Control 1998;9(4):417-24.

[32] Wolff M, Zeleniuch-Jacquotte A, et al. Risk of breast cancer and organochlorine exposure. Cancer Epidemiology, Biomarkers & Prevention 2000;9(3):271-7.

[33] Hoyer A, Jorgensen T, et al. Organochlorine exposure and breast cancer survival. Journal of Clinical Epidemiology 2000;53(3):323-30.

[34] Dewailly E, Ayotte P, et al. Susceptibility to infections and immune status in Inuit infants exposed to organochlorines. Environmental Health Perspectives 2000;108(3):205-11.

[35] Gladen B, Ragan N, Rogan W. Pubertal growth and development and prenatal and lactational exposure to polychlorinated biphenyls and dichlorodiphenyl dichloroethene. Journal of Pediatrics 2000;136(4):490-6.

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[39] Go V, Garey J, et al. Estrogenic potential of certain pyrethroid compounds in the MCF-7 human breast carcinoma cell line. Environmental Health Perspectives 1999;107(3):173-7.

[40] He F, Sun J, et al. Effects of pyrethroid insecticides on subjects engaged in packaging pyrethroids. British Journal of Industrial Medicine 1988;45(8):548-51.

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[42] Sumida K. Saito K, et al. Evaluation of in vitro methods for detecting the effects of various chemicals on the human progesterone receptor, with a focus on pyrethroid insecticides. Toxicology Letters 2001;118(3):147-155.

[43] Bazylewicz-Walczak B. Behavioral effects of occupational exposure to organophosphorous pesticides in female greenhouse planting workers. – Neurotoxicology 1999 Oct; 20(5): 819-26.

[44] Stephens R, Spurgeon A, et al. Neuropsychological effects of long-term exposure to organophosphates in sheep dip. Lancet 1995;345:1135-1149.

[45] Tenenbein M. Seizures after lindane therapy in adults. Veterinary and Human Toxicology 1990;32:363.

[46] Rao C, Shreenivas R, et al. Disseminated intravascular coagulation in a case of fatal lindane poisoning. Veterinary and Human Toxicology 1988;30:132-134.

[47] Davies J, Dedhia H, et al. Lindane poisonings. Archives of Dermatology 1983;119:142-144.

[48]Ravindran M. Toxic encephalopathy from chlorobenzilate poisoning: report of a case. Clinical Electroencephalograph 1978;9(4):170-2.

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