Pesticide Exposure During Pregnancy

Links to Learning Disabilities, Attention Deficit & Behavior Disorders


Pesticide exposure during pregnancy generates considerable concern as these chemicals are intentionally created to damage the nervous system. This concern is underscored upon realizing that all of us are continually exposed to pesticides. For example, in a governmental research project conducted by the National Institute of Environmental Health Sciences, Dr. Robert Murphy reported that in a large random sample of the general population, DDT was found in 100% of the blood samples tested at an average level of 3.3 parts per billion (ppb). Chlordane (a pesticide sprayed underneath homes for termite control and found to seep into the living airspace) was found in the blood of approximately 95% of the population (1). Other pesticides and chemicals found in over 90% of the population include dieldrin and hexachlorobenzene (Dieldrin is a food pesticide previously banned in the U.S. but is still used on foods imported from other countries). Information from a related Environmental Protection Agency project (based upon 6,000 urine samples) identified residues of six pesticide-related compounds, four carbamate-pesticide metabolites, and suspected eight metabolites of organophosphate insecticides (1).

Food sources contribute a significant amount of chemical residues. In an analysis of figures from the Florida Department of Agriculture in Tallahassee, Florida, it was shown that 19% of lettuce samples contained DDT (although DDT was banned it is still used on crops imported into the U.S. as well as being found as a contaminant in the frequently used citrus pesticide Kelthane). Also 65% of potatoes were found to contain the pesticide aldicarb (temik) which is nearly 100 times more poisonous that DDT (2).

A few interesting facts on pesticides were reported in a 1993 issue of USA Today Magazine (5):

  • One billion pounds of pesticides are added to the environment annually. If put in 100-pound sacks and laid end to end, they would encircle the planet.

  • The EPA estimates that one out of every 10 public drinking water wells in the U.S. contains pesticides, as well as more than 440,000 rural private wells. At a minimum, over 1,300,000 people drink water contaminated with one or more of these dangerous chemicals.

  • Pesticides have been found in thousands of lakes, rivers, and waterways throughout the nation. Agriculture is the number-one source of surface water pollution in the U.S.

In June, 1993, the National Academy of Sciences (NAS) released its long-awaited report on the health hazards posed to infants and young children from exposure to pesticides in the food supply. The Academy stated that any pesticides are harmful to the environment and are known or suspected to be toxic to humans. They can produce a wide range of adverse effects on human health that include acute neurologic toxicity, cancer, reproductive dysfunction, and possible dysfunction of the immune and endocrine systems. Among the NAS's critical findings, existing pesticide policies do not protect the young adequately, instead treating kids as "little adults." Unique dietary patterns are ignored, although they result in far greater exposure to multiple pesticides in food, by body weight, than occur in the adult population. The NAS expressed particular concern over children's dietary exposure to neurotoxic pesticides stating that children tend to retain a greater portion of a given dose of certain toxins than adults and are not as capable of detoxifying them in their bodies. They are at greater risk from neurotoxins since the nervous system in an infant or young child has not yet developed fully.

Indoor Air Contaminated with Pesticides

Home exposure is also a major route of pesticide exposure. Many homeowners routinely have the inside of their homes sprayed for roaches or ants with organophosphate or pyrethroid pesticides. In a study conducted by DOW Chemical and reported in Pest Control Technology Magazine (3), it was found that the pesticide Dursban, after being applied to the baseboards, was still present in the breathable air after 4 days at one-sixth the first day air level.

Another concern comes from the pesticide chlordane, now being detected in the majority of homes tested and is considered a health risk in many U.S. homes. Chlordane was used regularly as a termite preventive for over 30 years, finally being banned in 1988, but unfortunately, not before contaminating millions upon millions of U.S. homes. Although 100-200 gallons of the chemical is usually applied underneath the home's concrete foundation, it is now being found to migrate into the indoor air through either cracks in the foundation or around pipes entering the home. The principal of why this occurs is similar to that of a heavy boat sitting on the water that develops a pin-hole sized leak. Likewise, with a hundred ton home sitting on top of chlordane saturated sand - the high pressures underneath the home allow the vapors to be pulled into the lower pressures within the home. Other ways in which contamination can occur include accidental spills or through overspray saturation of the ceiling drywall boards if applied to the attic's wooden 2x4's.


The Majority of U.S. Homes Emit the Pesticide Chlordane
into the Indoor Air Living Space

A common misconception among the public is that pesticides used for termite or insect control don't find their way into the breathable air once applied. In fact, the long term exposure of home and building occupants from the evaporation of these chemicals has been found to continue in some cases for many decades after application and has resulted in the permanent evacuation of some buildings.

The rather startling figures coming in from testing homes throughout the U.S. show approximately 75% of homes built before 1988 are routinely being found to contain air levels of the pesticide chlordane. A study by Dr. Richard Fenske at Rutgers University in New Jersey found a whopping 34% of homes built before 1982 contained air chlordane levels over the safety limit of 5 micrograms per cubic meter of air, set by the National Academy of Sciences. There is no definite data on the number of homes in the United States that have been treated with chlordane, however, in 1987 the National Pest Control Association estimated that 1.5 million homes per year were treated for termite control (8). Taking the information from several studies regarding chlordane levels found in homes today, it could be estimated that 100-185 million U.S. residents are breathing questionable levels of chlordane in their homes daily and 10-20 million U.S. residents could be living in homes where the indoor air levels of chlordane are exceeding the recommended safe limits set by the National Academy of Sciences.

Once the scale of this problem is brought to the publics' attention, it should dwarf the concerns generated by indoor levels of formaldehyde and radon. In a review of the chlordane home contamination problem and its link to childhood cancers and blood disorders, Dr. David Ozonoff, of the Boston University School of Public Health stated, "a national program for monitoring all homes treated is urgently needed to detect persistent contamination (9).

If this wasn't enough to be concerned about, Dr. Ozonoff's went on to say,

"It should also be noted that commercial chlordane formulations contain carcinogenic "inert ingredients" and contaminants, such as propylene oxide, hexachlorobutadiene, and carbon tetrachloride, apart from some 40 other ingredients so far undisclosed by the manufacturer, formulators and applicators of C/H (chlordane/heptachlor)."


Chlordane Causes Neurological Disorders
A.D.D Symptoms in 216 Adults Tested

Environmental Health Perspectives, 103:690-694, 1995

In 1987, over 250 adults and children were exposed to the pesticide chlordane when the wooden building surfaces and soil around their apartment complex was sprayed. Their exposure came from the vapors that entered into their home for the years after the chemical's application. Levels inside the homes were reported above 0.5 mcg/m3.

In June-September 1994, 216 adult occupants or former residents of the apartment complex were examined by researchers at the University of Southern California School of Medicine in Los Angeles. The 109 women and 97 men were given a battery of neurological tests to determine if the low levels of chlordane in their apartments was causing any harmful effects. The tests given are considered sensitive indicators of neurotoxicity. To determine if chlordane was in fact causing neurological problems, the test scores of the chlordane exposed adults were compared to the test scores of 94 women and 68 men from Houston, known not to have been exposed to chlordane.

Results of the testing showed many negative effects upon mental function from the low levels of air chlordane. Not only were test scores lower for reaction time, balance, and memory, but also worse scores were observed in the test checking for attention deficits (digit symbol) and all tests of mood scores including tension, depression, anger, vigor and fatigue. A summary of these tests are listed on the following page.

Test Scores for Adults Living in Homes with
Chlordane Identified in Indoor Air

Neurological Test Given How chlordane group compared:
exposed vs.
Chlordane Exposed Adults Non-Exposed Adult
Simple Reaction Time

34% slower

414 milliseconds

309 milliseconds

Balance measured as sway speed

16% more swaying .95 cm/sec .82 cm/sec

Memory recall of story details (WAIS)

20% less recall 8.4 10.4
Digit Symbol
(tests attention)
19% slower 48.5 57.5
Vocabulary Score 12% slower 16.0 18.0
Mood State Sore - Tension 70% more 18.5 10.9
Mood State Score - Depression 74% more 20.7 11.9
Mood State Score - Anger 69% more 18.2 10.8
Mood State Score - Vigor 27% less 12.4 17.1
Mood State Score - Fatigue 75% more 14.2 8.1
Mood State Score - Confusion 11% more 6.0 5.4

Going beyond the neurological testing, both groups were also investigated for many common symptoms and illnesses. Those which were significantly more common in the chlordane exposed group included asthma, allergies, production of phlegm, chronic bronchitis by Medical Research Council criteria, and wheezing with and without shortness of breath. Headaches and indigestion were also more common among the chlordane exposed individuals.

In summary Dr. Kilburn and Thornton summarized their findings by stating,

"The exposure of our study group appears to be from indoor air, due to the outgassing of chlordane from the wooden surfaces of the apartment complex... Examination of subjects exposed in their homes to chlordane as compared to referent subjects showed significant, and we suggest important, impairment of both the neurophysiological and psychological functions including mood states. Accompanying these changes were significant differences in symptom frequency and in respiratory rheumatic and cardiovascular disease symptoms. The most notable changes were slowing of reaction time, balance dysfunction as revealed by increased sway speed, reduction in cognitive function, perceptual motor speed, and immediate and delayed verbal recall... The neurobehavioral impairments measured in this environmental epidemiological study were similar to those noted in patients exposed to chlordane at home. These impairments include probably irreversible dysfunction of the brain. Possible effects on trigeminal nerve-pons-facial nerve function were suggested for the first time. Confirmatory studies, including follow-up after removal from exposure, are urgently needed. Meanwhile, chlordane use should be prohibited worldwide."

This study should generate heightened concern because of the large number of neurological and health effects seen at chlordane air levels of above 0.5 mcg/m3 (typical levels for most U.S. homes) and statements by researchers that developing children are harmed more by chemicals than adults.

Dr. Kaye H. Kilburn and John C. Thornton
Environmental Sciences Laboratory
University of Southern California School of Medicine, Los Angeles

Home Pesticide Flea Treatments
Cause Short-Term "Illegally" High Air Levels

American Journal Public Health, 80(6):689-693, 1990

Applying common flea pesticide treatments to carpets results in illegally high air pesticide levels in homes which lasts for over 24 hours after application. This was the conclusion of research conducted by Dr. Richard A. Fenske, Assistant Professor at Rutgers University.

Tests were conducted by applying the common pesticide Chlorpyrifos (Dursban) for flea treatment by a licensed Pest Control Applicator to three rooms of an unoccupied apartment in New Jersey in June, 1987. Air sampling equipment was installed above the floor at the levels expected for an adult sitting in a chair and that of an infant. After application, samples were taken at 30 minutes, 1 hour, 1.5 hours, 3 hours, 5 hours, 7 hours and 24 hours. Results showed that at 5 hours post application, indoor air levels of the pesticide was nearly twice above the legal limit in homes with ventilation (an open window) and over 6 times above the legal limit at 7 hours where windows were closed. Levels at the infant breathing zone was nearly 10 times above the legal limit at 7 hours and over 3 times the legal limit even after 24 hours.

These results show it is incorrect when Pesticide Applicators state it is safe to return home several hours after application. In fact, levels at 7 hours were 3-5 times higher than the 1.5 hour level.

In conclusion the researchers state,

Despite uncertainties in exposure/absorption estimates and toxicological interpretation, the dose values derived in this study raise a public health concern. Broadcast applications and possibly total release aerosol/fogging applications of acutely toxic insecticides may result in dermal and respiratory exposures sufficient to cause measurable toxicological responses in infants.

Dr. Richard A. Fenske, Ph.D., Kathleen Black, MPH, Kenneth P. Elkner, MS
Department of Environmental Sciences and Graduate Program in Public Health
Rutgers University

Common Pesticides Cause Hyperactivity
in Test Animals after Single Dose

Neurotoxicology and Teratology, Vol. 11:45-50, 1989

Groups of test animals exposed to different pesticides used in agriculture and lawn care showed over 50% more activity following a single exposure to the chemical. One of the main goals of this experiment, conducted by Dr. J. A. Mitchell and colleagues at the University of Michigan, was to investigate activity behavioral changes in test animals (male Swiss mice) following a single exposure to one of 4 different dosages of weed killers and fungicides. The chemicals used included Lasso (containing alachlor), Basalin (containing fluchloralin), Premiere (containing dinoseb) and the fungicide Maneb-80 (80% Maneb).. Test dosages ranged from a very low .4 mg/kg to 4 mg/kg to 40 mg/kg. Even the largest dose was still below the LD-50 for the animals (the amount needed to kill 50% of the test animals). According to the researchers, the herbicides and fungicides have received few reports investigating their toxicity while their yearly growth and production have grown far more than the insecticides.

The detection of hyperactivity was measured by placing the test animals in steel cages that were equipped with electronic motion detectors which used infrared beams to count specific movements by the animals. After the single chemical exposure, activity was measured for a 4 hour period. Results showed the weed killer "Lasso" did not show any effects at the very low .4 mg/kg level but did show over a 65% increase in activity at the low 4 mg/kg and a 75% increase at the higher 40 mg/kg level. The weed killer Dinoseb also showed no activity increases at the lowest .4 mg/kg dose but did show a 15% increase at the 4 mg/kg level and a 54% increase at the larger 40 mg/kg level. Other researchers have reported that activity provides a sensitive measure for evaluating the behavioral effects of the pyrethroid pesticide, deltamethrin, at doses that did not cause the characteristic neurotoxicological syndrome (6).

In conclusion the researchers stated,

"The results of this study suggest that at least some herbicides, in addition to pyrethrins, organophosphate, and carbamate pesticides, can produce behavioral manifestations following accidental exposure...The effects of the pesticides on activity also support the hypothesis that these agents may affect the central nervous system."

Dr. J. A. Mitchell, S. F. LongDept. of Pharmacology, University of Mississippi
The Behavioral Effects of Pesticides in Male Mice
Neurotoxicology and Teratology, Vol. 11:45-50, 1989

Pesticides Mimic Human Hormones
Reproductive System Damage Suspected

Scientific American, September, 1993

Pesticides and other chemicals are being found to resemble the hormone estrogen, thereby creating serious problems for the reproductive system, according to research by Dr. Richard M. Sharpe of the University of Edinburgh and Dr. Niels Skakkebaek of the University of Copenhagen. The substances that concern the researchers most include DDT, PCB's, dioxins, and some petroleum by-products.

Sperm count, according to Skakkebaek, has taken a "nose-dive" during the past half century. They looked at 61 papers on male fertility published between 1938 and 1990, covering data on almost 15,000 men from around the world. According to Skakkebaek and his Danish colleagues, the mean sperm count had declined from 113 million per milliliter in 1940 to only 66 million per milliliter in 1990. Moreover, the volume of semen in a single ejaculation had also fallen from 3.40 to 2.75 milliliters. Those figures suggest that, on average, men now produce less than half as many sperm as did men 50 years ago.

Chemicals with affinities for estrogen receptors on cells could cause these problems, state the researchers. Animal studies have shown that if male fetuses are exposed to high doses of estrogens, they may develop with many female characteristics. Lower doses may alter the differentiation and multiplication of the germ cells that eventually give rise to sperm, the researchers note

Dr. John A McLachlan, director of intramural research at the National Institute of Environmental Health Sciences states, "some of the environmental chemicals that have estrogenic activity also seem to have a long half-life and can bioaccumulate" in the body's fat. One group, he explains, looked at the effects of the insecticide kepone that is only weakly estrogenic. At first, female rats exposed to part-per -billion levels of kepone showed no effects, but after about nine weeks of exposure the chemical reached potent levels, and the animals' reproductive systems locked into a perpetual ovulatory state. The World Wildlife Fund has gathered evidence that some seagulls, fish and other creatures in polluted areas exhibit abnormal reproductive behavior or physiology.

Malignant Mimicry
Scientific American, September, 1993


Hydrocephaly & Cleft Palete Birth Defects
Occur After Pesticide Exposure

Bulletin of Environmental Contamination Toxicology, 54:363-369, 1995

Of the many different types of pesticides (which include insecticides, herbicides and fungicides), it was found that the common fungicide "cyproconazole" caused serious defects when administered to test animals. This chemical is reported to be widely used in agriculture and is a member of the family of fungicides known as triazole fungicides. Its closely related family members include the fungicides triadimefon, triadimenol, bitertanol, flusilazole, 1,2,4-triazole, and propiconazole. Each of these pesticides were reported in this article as being capable of causing birth defects in test animals when administered at doses as low as 30 mg/kg. These chemicals are far more toxic than even standard insecticides. The "No Observable Effect Level" (which means the maximum amount of the chemical that test animals can be exposed to without seeing any adverse effects) is reported to be only 2 mg/kg for flusilazole.

The study on the effects of cyproconazole (lets call it CPZ for simplicity) was headed by Dr. K. Machera, at the Laboratory of Pesticide Toxicology in Athens, Greece. Dr. Machera exposed 10 pregnant animals to different levels of CPZ ranging from 20-75 mg/kg from the 6th to the 16th day of pregnancy. On the 21st day of pregnancy the animals were sacrificed and the number of implantations, resorption sites and live and dead fetuses were recorded. The fetuses were weighed and examined for abnormalities.

Results showed the number of resorptions (similar to an early miscarriage) was over 8 times greater for the animals exposed to the 50 and 75 mg/kg doses. The fetal length was significantly smaller in doses from 50 mg/kg up. The fetal body weight was significantly less even at the lowest dose of 20 mg/kg.

Cleft Palate did not occur in any of the 100 offspring not exposed to CPZ. However, cleft palate did occur in 2% of animals exposed to 20 mg/kg of CPZ, 20% of animals exposed to 50 mg/kg of CPZ and 91% of animals exposed to the highest 100 mg/kg dose.

The same trend was also seen with hydrocephalus - 0% for the animals not exposed to CPZ, 6% for animals exposed to 20 mg/kg, 19% for animals exposed to 50 mg/kg, 32% for animals exposed to 75 mg/kg and 100% for the 12 animals exposed to the 100 mg/kg level.

These studies demonstrate the definite potential for pesticides in the triazole family to increase the risk of lower birthweight, lower body length, as well as strongly increasing the risk of cleft palate and hydrocephalus. With results such as this in test animals, it would certainly be worthwhile to investigate the incidence of these conditions among people living in close proximity to agricultural areas. Dr. Machera did not state if these chemicals were used on residential lawns as an anti-fungal agent. Keep in mind that these studies were looking for physical defects and were not looking for neurological defects in offspring (which typically occur at much lower dosages).

Dr. K. Machera
Laboratory of Pesticide Toxicology
Benaki Phytopathological Institute
Athens, Greece

Combining Several Pesticide Ingredients
Increases Neurological Damage

Journal of Toxicology and Environmental Health, 48:35-56, 1996

Military personnel operating in the Persian Gulf region between August 1990 and April 1991 have complained of numerous neurological complications after returning home. Several theories have been expressed regarding the occurrence of these problems. One definite fact of exposure to potentially neurotoxic compounds is that soldiers used large amounts of the chemicals DEET (a personal insect repellent) and the pesticide permethrin. Soldiers were also given the drug pyridostigmine bromide (PB) to protect against possible nerve gas attack.


Because of this concern, scientists at the Neurotoxicology Division at the Environmental Protection Agency (EPA) and three other Universities conducted a long term study to determine the effects of combining these chemicals and then observing their effects upon the nervous system of test animals.

The study was conducted by exposing four groups of five hens each to either one or several of these chemicals and at different doses. Researchers continued the exposure daily to the animals for approximately 60 days. During this period investigators looked for various signs of health problems including neurotoxicity.

Results showed animals treated with only PB revealed no difference between controls upon neuropathological examinations (investigations of tissue samples under a microscope). Some animals treated with permethrin or DEET exhibited minor neuropathological changes that consisted of a small increase in the frequency of slightly enlarge axons. (Axons are the main connections between brain cells which send information).

Regarding the effects of combining the chemicals, the researchers stated that the animals treated with the DEET/permethrin combination developed "hyperexcitability" between 1 and 4 weeks of dosing. In one animal, a mild gait disturbance was detectable at 27 days that progressed to a stumbling and unsteady gait accompanied by moderate fine body tremors. Microscopic examination of spinal cord and sciatic nerve found mild neuropathological alterations in two of the animals treated with permethrin/DEET which included a significant increase in both the frequency and degree of enlargement of the axons.

One point of neurotoxic interest - even though the dosages of permethrin were well below the amount needed to kill the animals, it was found that when permethrin was combined with DEET it created brain damage within the test animals that is "similar to those observed following near lethal doses of permethrin."

In conclusion the scientists stated,

This study demonstrates that concurrent administration of any two compounds of PB, DEET, and permethrin results in neurotoxicity that is markedly greater than that resulting from treatment with any individual compound. ....Both DEET and permethrin have been shown to produce tremors and hyperexcitability in experimental animals (Ambrose et al., 1959; Schoening et al., 1993).... In addition, these findings suggest the need for additional studies into potential health risks associated with coexposure of humans to these agents at dosages likely to have been used by the Gulf War veterans.Generating further concern for the pesticide permethrin, is that research has found the chemical undergoes a biological transformation within the human body by what is called esterase and oxidase inhibitors (for the benefit of our scientifically minded), thereby creating a new chemical which researchers say,

".....may create unanticipated hazards by enhancing pyrethroid toxicity to mammals." (4)

In other words, they are saying that this chemical is most likely more dangerous than displayed by tests with animals since the human body has the potential to change the chemical into an entirely new and even more toxic chemical."

DEET is an aromatic amide used as a personal insect repellent against mosquitoes, biting flies, and ticks, among other insects. It has been used since 1946 by the U.S. Army and since 1957 by the general population. Approximately 30% of the U.S. population uses DEET as a lotion, stick, or spray at concentrations between 10 and 100% active ingredient. Extensive and repeated topical applications of DEET resulted in human poisoning including two deaths. Symptoms of poisoning are characterized by tremor, restlessness, slurred speech, seizures, impaired cognitive functions, and coma (McConnell et al., 1986). DEET has been found to be efficiently absorbed through the skin (Windheuser et al., 1982; Spencer et al., 1979). Also, regarding the use of permethrin, this chemical is currently used in schools and homes for general insect or termite treatments. Erroneously, pesticide applicators state that this chemical is the same as pyrethrin (which is a natural pesticide made from the chrysanthemum flower). This is very inaccurate. Although the molecules are somewhat similar, they are still very different and pyrethroid pesticides such as permethrin are showing increased evidence in the medical research of a variety of neurological and immune system damaging effects (3).

Karl F. Jensen
Neurotoxicology Division
U.S. Environmental Protection Agency, Research Triangle Park, NC

CHEM-TOX COMMENTS: Although pesticides are tested for many health
effects such as cancer, skin irritation, fatality risk, and major birth defects, they are
currently not required to be tested for subtle neurological effects such as with memory,
learning problems or effects upon behavior.

Additional References

Science News, "Pesticides: The Human Body Burden"
September 24, 1983, pg. 199

Journal Of Toxicology And Environmental Health, 48:215-229, 1996
Clinical Immunotoxicity of Pesticides
T. Vial, B. Nicolas, J. Descotes
Department of Pharmacology and Medical Toxicology, Lyon, France

Journal Of Agricultural And Food Chemistry, 20:944-950
Potentiation Of Toxicity Of Organophosphorus Compounds Containing Carboxylic Acid Functions Toward Warm-Blooded Animals By Some Organophosphorus Impurities.
Pelligrini, G., and Santi, R., 1972.

USA Today Magazine, November 1993, pg. 51(3), Al Meyerhoff

Neuroscience. Biobehavioral. Reviews, 5:270-294, 1981
Drugs And Taste Aversion
Rondeau, D. B., Jolicoeur, F. G., Merkel, A. D., Wayner, M. J.

Bulletin Environmental Contamination Toxicology, 39:903-910, 1987
Indoor Air Levels of Chlordane in Residences In New Jersey
Department of Environmental Science, Cook College, Rutgers University, NJ
Richard Fenske, Todd Sternbach

Environmental Facts: EPA Statement on Aldrin Termiticides," 1983
Environmental Protection Agency, Region 2, New York: Washington, DC

Teratogenesis, Carcinogenesis, and Mutagenesis, 7:527-540, 1987
Leukemias and Blood Dyscrasias Following Exposure to Chlordane and Heptachlor
School of Public Health, University of Illinois Medical Center,
Environmental Health Section, Boston University School of Public Health
Boston, Massachusetts