April 29, 1999


For the past 25 years, tens of millions of Americans in hundreds of cities and towns have been drinking tap water that is contaminated with low levels of insecticides, weed killers, and artificial fertilizer. They not only drink it, they also bathe and shower in it, thus inhaling small quantities of farm chemicals and absorbing them through the skin. Naturally, the problem is at its worst in agricultural areas of the country.

The most common contaminants are carbamate insecticides (aldicarb and others), the triazine herbicides (atrazine and others) and nitrate nitrogen.[1] For years government scientists have tested each of these chemicals individually at low levels in laboratory animals -- searching mainly for signs of cancer -- and have declared each of them an "acceptable risk" at the levels typically found in groundwater.

Now a group of biologists and medical researchers at the University of Wisconsin in Madison, led by Warren P. Porter, has completed a 5-year experiment putting mixtures of low levels of these chemicals into the drinking water of male mice and carefully measuring the results. They reported recently that combinations of these chemicals -- at levels similar to those found in the groundwater of agricultural areas of the U.S. -- have measurable detrimental effects on the nervous, immune and endocrine (hormone) systems.[2] Furthermore, they say their research has direct implications for humans.

Dr. Porter and his colleagues point out that the nervous system, the immune system, and the endocrine (hormone) system are all closely related and in constant communication with each other. If any one of the three systems is damaged or degraded the other two may be adversely affected. The Wisconsin researchers therefore designed their experiments to examine the effects of agricultural chemicals on each of the three systems simultaneously. To assess immune system function, they measured the ability of mice to make antibodies in response to foreign proteins. To assess endocrine system function, they measured thyroid hormone levels in the blood. And to assess nervous system function they measured aggressive behavior in the presence of intruder mice introduced into the cages. They also looked for effects on growth by measuring total body weight and the weight of each animal's spleen.

The experiments were replicated many times, to make sure the results were reproducible. They found effects on the endocrine system (thyroid hormone levels) and the immune system, and reduced body weight, from mixtures of low levels of aldicarb & nitrate, atrazine & nitrate, and atrazine, aldicarb & nitrate together. They observed increased aggression from exposure to atrazine & nitrate, and from atrazine, aldicarb & nitrate together.

The Wisconsin research team wrote, "Of particular signficance in the collective work of Boyd and others,[3] Porter and others,[4] and our current study[2] is that THYROID HORMONE CONCENTRATION CHANGE was consistently a response due to mixtures, but NOT usually to individual chemicals." [Emphasis in the original].

In the five-year experiment, thyroid hormone levels rose or fell depending upon the mixture of farm chemicals put into the drinking water. Dr. Porter and his colleagues present evidence from other studies showing that numerous farm chemicals can affect the thyroid hormone levels of wildlife and humans. PCBs and dioxins can have similar effects, they note. Proper levels of thyroid hormone are essential for brain development of humans prior to birth. Some, though not all, studies have shown that attention deficit and/or hyperactivity disorders in children are linked to changes in the levels of thyroid hormone in the blood. Children with multiple chemical sensitivity (MCS) have abnormal thyroid levels. Furthermore, irritability and aggressive behavior are linked to thyroid hormone levels.

Interviewed recently by Keith Hamm of the SANTA BARBARA [CAL.] INDEPENDENT,[5] Dr. Porter explained, "Earlier work had shown that thyroid hormone typically changed when exposure to these pesticides occurred. Thyroid hormone not only affects and controls your metabolic rate, that is, how fast you burn food, it also controls your irritability level. For example, Type A personalities are more assertive, more aggressive, more hyper. These people tend to have higher levels of thyroid hormone. Type B personalities--people that are really laid back, really take things very easily--have lower levels of thyroid hormone. We expected that changes in thyroid [would] change irritability levels. This was a concern because there was information that kids are getting more hyper and [that their] learning abilities are going down," Dr. Porter said.

A recent study of 4 and 5 year-old children in Mexico specifically noted a decrease in mental ability and an increase in aggressive behavior among children exposed to pesticides.[6] Elizabeth A. Guillette and colleagues studied two groups of Yaqui Indian children living in the Yaqui Valley in northern Sonora, Mexico. One group of children lives in the lowlands dominated by pesticide-intensive agriculture (45 or more sprayings each year) and the other group lives in the nearby upland foothills where their parents make a living by ranching without the use of pesticides. The pesticide-exposed children had far less physical endurance in a test to see how long they could keep jumping up and down; they had inferior hand-eye coordination; and they could not draw a simple stick figure of a human being, which the upland children could readily do.

Notably, in the Guillette study we find this description of the behavior of pesticide-exposed children: "Some valley children were observed hitting their siblings when they passed by, and they became easily upset or angry with a minor corrective comment by a parent. These aggressive behaviors were not noted in the [pesticide-free] foothills [children]."

The human body can defend itself against poisons to some degree, but Dr. Porter and his colleagues describe ways in which low-level mixtures of pesticides and fertilizer might get past the body's defenses:

The body is prepared to protect itself against poisons taken by mouth. The liver begins to produce enzymes that try to break down fat-soluble chemicals. However, if a poison enters through the lungs or the skin, the body does not offer the same kind of defenses. Furthermore, the body's ability to put up defenses may be compromised by taking certain medications (e.g., antibiotics), or by receiving "pulses" of toxins rather than a steady dose.

Receiving "pulses" of poisons would be normal in the case of agricultural poisons which are sprayed onto crops only at certain times of the year. During those periods, people living near sprayed fields might get a sudden dose of poison via their lungs, their skin and their drinking water. Dr. Porter describes such a situation this way:

"Imagine [that] you're standing in a boxing ring and a boxer jumps in with you, and he walks toward you smiling with his hand outstretched. And you reach out to shake his hand and he smacks you in the stomach as hard as he can. And when you bring your arms up to defend yourself, he backs away. Finally you get tired of holding your defenses up and you drop them and he rushes in and smacks you again. That's the physical equivalent to a 'pulse dose,' which is normally what we tend to get exposed to.

"The defenses we have take a while to induce, just like it takes a while to bring your arms up. It takes anywhere from a half a day to five days to induce those [defenses] to appropriate levels. If you're in a particular stage of your hormone cycle or you're taking some antibiotics, it can compromise your ability to defend yourself even if you did have enough time to induce your defenses. If you've got pulse doses coming in under your defenses or coming in faster than you can bring your defenses up then you've got a situation where you're totally vulnerable.

"If you've got a pregnant mom, for example, in day 20 when the fetus's neural tube is closing and she gets an exposure, she hasn't had enough time to induce her defenses. Her thyroid level goes up or goes down, the hormone crosses the placenta and can permanently alter the developmental pattern of the fetus's brain. And then the pulse dose is gone, you have no detection, mom doesn't even know she's pregnant, and you may have an offspring that is neurologically compromised and wonder, 'How did this happen?'"

In the interview with Keith Hamm, Dr. Porter expressed concern for the overall effect of pesticides on the nation's children:

Hamm: "Are pesticides, herbicides, and fertilizer used more or less these days than fifty years ago and have the toxicities changed?"

Porter: "The usage has continued to climb. There's an enormous amount of these [chemicals being used] right now. There was a recent study that examined the urine of people across the country, [asking] if people are being exposed. On average, anywhere from five to seven compounds were being excreted. There's a great deal of expo- sure to the general populace.

"And yes, the toxicities have definitely changed. [Some toxicities are now measured] in the parts-per-trillion range. I would point out that fetuses are sensitive to chemicals in the parts per quadrillion range."

Hamm: "I would assume that most people in this country are eating conventionally grown food. If that's the case, wouldn't the problems be more apparent? Why are there not more hyperaggressive dim-witted people with poor immune systems?"

Porter: "If we really looked carefully at what's been happening in this county, you might find exactly that happening."

Because of recent violence in small cities and towns (such as Littleton, Colorado, Laramie, Wyoming, and Jasper, Texas), this is a time when Americans are searching for the causes of violence in their society. Some are blaming a decline in religious upbringing. Others are blaming households with the parents working and no one minding the kids. Some say the cause is violent movies, violent TV and extremist internet sites, combined with the ready availability of cheap guns. Still others point to a government that has often sanctioned the violence of "gunboat diplomacy" to open foreign markets for U.S. corporations.

No one seems to be asking whether pesticides, fertilizers and toxic metals [see REHW #529, #551] are affecting our young people's mental capacity, emotional balance, and social adjustment. From the work of Warren Porter, Elizabeth Guillette and others, it is apparent that these are valid questions.

--Peter Montague

April 22, 1999


In all industrialized societies, both men and women are often exposed to organic solvents at work and in the home. Gasoline contains a mixture of organic solvents, and solvents are major components of lighter fluid, spot removers, many aerosol sprays, paints, paint thinners, paint removers, fingernail polish and remover, glues, and floor and tile cleaners.

In the past year or so, half a dozen studies have implicated solvents in several serious health problems, including major birth defects, immune system disorders (such as rheumatoid arthritis, scleroderma, and lupus erythematosus), and several kinds of cancer, including breast cancer.

Chemicals in the "organic solvent" class include aliphatic hydrocarbons (mineral spirits, varnish, kerosene), aromatic hydrocarbons (benzene, toluene, xylene), chlorinated hydrocarbons (carbon tetrachloride, trichloroethylene, tetrachloroethylene [also known as perchloroethylene, or perc]), aliphatic alcohols (methanol), glycols (ethylene glycol), and glycol ethers (methoxyethanol). There are hundreds of different organic solvents on the market and it is rare to be exposed to only one at a time; mixtures are common.


Several occupations dominated by women have potential exposure to organic solvents: health care professions, work in the clothing and textile industries, and the graphic arts, among others.

In 1998, an analysis of five previous studies showed that women exposed to organic solvents during pregnancy had a 64% increased chance of giving birth to a baby with a major birth defect.[1] A major birth defect was defined as "potentially life-threatening or a major cosmetic effect." However, all five studies were retrospective in design -- that is, women were asked after the birth of their child whether they had been exposed to solvents during pregnancy. All retrospective studies can suffer from "recall bias." For example, people who give birth to defective babies may have a heightened or otherwise distorted recollection of what chemicals they were exposed to during pregnancy, compared to women who gave birth to normal children.

Just last month, a "prospective" study of solvents and birth defects was published in the JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION (JAMA).[2] The study was "prospective" because women were asked about their solvent exposure during pregnancy before they gave birth. Thus a "prospective" study avoids the problem of "recall bias."

The JAMA study found that women occupationally exposed to solvents during pregnancy have a 13-fold increased chance of giving birth to a child with a major birth defect. A major birth defect was defined as "any anomaly that has an adverse effect on either the function or the social acceptability of the child." Defects that occurred in babies born to women in the solvent-exposed group included heart valve defects; soft cartilage in the larynx; micropenis [abnormally small penis]; deafness; clubfoot; neural tube defect [opening to the spinal cord at the base of the brain]; and hydronephrosis [a serious kidney defect].

The JAMA study examined 125 women who were occupationally exposed to organic solvents during pregnancy and an equal number of pregnant controls matched for age, number of previous pregnancies, smoking and drinking habits. In addition, the control group had been exposed to chemicals known not to produce birth defects.

All the exposed women worked with organic solvents for at least the first 13 weeks of pregnancy. The most common occupations were factory worker; laboratory technician; professional artist or graphic designer; and printing industry worker. Other solvent-exposed occupations included chemist; painter; office worker; veterinary technician; funeral home worker; carpenter; social worker; and car cleaner.

The two groups of pregnant women differed in several noteworthy respects. Both groups had had an equal number of pregnancies, but the solvent-exposed women had had significantly more miscarriages (and thus fewer children born). Babies born to solvent-exposed women weighed an average of 168 grams (5%) less than babies born to the control group. Eight babies born to solvent-exposed women fell in the category "low birth weight" (defined as less than 2500 grams [1.1 pounds].) Among non-exposed women, 3 babies had low birth weight. Among the solvent-exposed group, 17 babies suffered "fetal distress" at birth vs. 6 with fetal distress among the unexposed group. Fetal distress was defined as fetal intestinal discharge during delivery and/or abnormal fetal heart rate during delivery, or the requirement of resuscitation or a neonatal intensive care unit.

Among the 125 women occupationally exposed to solvents, 75 reported symptoms temporarily associated with their exposure, 43 had no symptoms of exposure, and for 7 such information was missing. Twelve of the 13 major birth defects occurred among the group reporting symptoms of exposure. The exposed women were further divided into two groups -- those exposed for 7 months or longer; and those exposed for 3 to 7 months. Sixteen women exposed more than 7 months had labor with fetal distress vs. only one among those with shorter exposure.

Organic solvents can readily pass from the mother to the fetus in the womb, by passing through the placenta. The authors conclude that pregnant women are endangered by occupational exposure to solvents, and so are their babies, particularly if the mother has symptoms of solvent exposure herself.


Rheumatoid arthritis, lupus, and scleroderma are "rheumatoid" disorders affecting the body's connective tissues. These are all "autoimmune" diseases in which the body's immune system makes too many antibodies, which are proteins usually directed against invaders. In the case of autoimmune diseases, the antibodies are mistakenly directed against the self.

If a person has several of the symptoms of these three "rheumatoid" diseases but not enough of the symptoms of any one disease to be diagnosed with that disease, they will be diagnosed as having "undifferentiated connective tissue disease" (UCTD). For reasons that are unknown, rheumatoid diseases strike women somewhat more than men.

A recent case-control study of 205 women in Ohio and Michigan with UCTD, and 2095 controls, revealed that the women with UCTD were 3 times as likely as controls to have been exposed occupationally to paint thinners and paint removers.[3] Paint thinners include mineral spirits, white spirit, naphtha, VM & P naphtha, Stoddard Solvent and Varsol, all of which are petroleum distillates. Furthermore, women with undifferentiated connective tissue disease were twice as likely as controls to have been exposed on the job to mineral spirits.

Women in specific solvent-related occupations had a greatly-increased chance of getting UCTD, compared to controls. Women in the furniture refinishing industry had a 9-fold increased chance of getting UCTD; women in perfume, cosmetic or drug manufacturing had a 7-fold increased chance; women in rubber product manufacturing had a nearly 5-fold increased chance of getting UCTD.

The causes of rheumatoid diseases are not known, but something triggers the immune system to attack the self instead of restricting its attack to non-self invaders such as bacteria and viruses. This carefully-done study indicates that petroleum-based solvents may be one such trigger.


Benzene, toluene, xylene and styrene are the cornerstones of the petrochemical industry. They serve as the feedstock for the manufacture of many other solvents, chemical intermediates, dyes, explosives, and resins for the manufacture of plastics, elastomers, and textiles. Many solvents contain benzene, toluene and/or xylene in varying proportions.

Of these four large-volume chemicals, only benzene has been clearly established as a human carcinogen. Benzene can cause leukemia (cancer of the blood-forming cells) in exposed workers and perhaps in others who have lesser exposures.

Based on studies of laboratory animals, styrene is a suspected human carcinogen, but toluene and xylene fall in the "unknown" category, chiefly because they have hardly been studied.

Last year a large case-control study in Canada examined the experience of 3730 patients with 15 different kinds of cancer. The authors of the study reported finding "limited evidence" of an association between xylene and colon cancer; between benzene, toluene and styrene and cancer of the rectum; and between styrene and prostate cancer.

Most interestingly, a 1997 study examined the relationship between breast cancer and solvents. There is evidence from studies of laboratory animals that solvents can cause breast cancer in some species. In humans, the evidence is spotty. Out of 17 studies of occupational solvent exposure and cancer, 12 have shown no relationship while 5 have indicated that breast cancer and solvents are related.[5] On the other hand, only one of the 17 studies was specifically designed to look for breast cancer, and women often make up a tiny proportion of an occupational cohort so most studies do not have the necessary power to reveal a relationship even if one exists.

Canadian researchers France P. Labreche and Mark S. Goldberg have offered a formal hypothesis linking breast cancer to solvents.[5] They point out that the breasts of women in industrialized countries contain numerous solvents dissolved in the fatty tissues. Breast milk contains acetaldehyde, benzaldehyde, benzene, carbon disulfide, carbon tetrachloride, chlorobenzene, chloroethane, ethyl chloride, chloromethane, chloropentane, crotonaldehyde, cyclohexane, cyclopentane, dichlorobenzene, 1,2-dichloroethane, dichloroethylene; ethyl alcohol, ethylbenzene, and perhaps other solvents as well.[5] (Despite the presence of these industrial poisons in breast milk, breast feeding is still the best way to nourish an infant; all alternatives are worse.) Often these solvents are present in breasts at higher concentrations than in a woman's blood stream.

These solvents remain in breast tissue for long periods, in contact with the very cells where cancers originate, Labreche and Goldberg point out. Some of these solvents have estrogenic properties, but Labreche and Goldberg are mainly concerned that many solvents and their metabolic byproducts are, themselves, capable of initiating, or promoting cancers. Labreche and Goldberg, and perhaps others, have studies underway now to test the solvents-cause-breast-cancer hypothesis.

--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)



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