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For Your Health

A Tribute and A Triumph:
The Rachel Carson Council
Conference on Cancer and Pesticides

October 26, 1996

The overarching goal of our Cancer and Pesticides conference was to honor Rachel Carson, whose Silent Spring alerted citizens to chemicals' harm, including their capacity to cause cancer, and whose courageous personal struggle against malignancy ended in 1964, with her death from complications related to breast cancer. Since then, cancer rates have increased in the U.S. and ever-greater pesticide sales reflect the nation's continued reliance on chemicals. Our conference brought together activists, academics, researchers, lay persons, and students in a healthy atmosphere for structured, effective and considerate communication about this worrisome but not completely unexpected coincidence.

The highly competent speakers, the attentive, animated audience, a delicious organic lunch, glorious October weather and the inspiring surroundings of the Patuxent Wildlife Visitors Center all contributed to the event's success. A sampling of participants' opinions reflect their diversity and general concurrence that the Conference was a triumph: "Amazing gathering of expertise"... "Excellent"..."Very intense solid speakers"..."Not enough time"..."Saw a Bald Eagle on the break".."Yummy lunch"..."Repeat conference next year in same place."

Speakers included: Dr. David Pimentel, Dr. Willie Lijinsky, Dr. Carl Barrett, Dr. John Reif, Dr. John Harshbarger, Dr. Janette Sherman, Dr. Jeff Baubier, Dr. Sam Epstein, Dr. Mary Ward, Dr. Marion Moses, Dr. Jim Davis, Dr. Beverly Paigen and Dr. Aaron Blair. Speakers addressed the following pertinent issues (with updates provided where possible):

1) Certain cancers have been associated with specific pesticides.

Age-adjusted cancer rates (in which the increased number of older people has been taken into account) are rising in the general population of developed countries. Certain cancers which have been related to specific pesticides also are increasing. They include: brain cancer, non-Hodgkin's lymphoma (NHL), and prostate cancer.

The strongest and most consistent association exists for non-Hodgkin's lymphoma (NHL) and the phenoxy herbicides (such as 2,4-D).

Other associations found are:

[Note: Individual cancers are associated with exposures to pesticides in general (see #3).]

2) Breast cancer incidence rates have risen significantly since Rachel Carson's death in 1964.

Between 1973 and 1991 the incidence rate for breast cancer in the U.S. increased 25%. Dr. Janette Sherman stated that breast cancer has been linked with the endocrine effects of chemicals. Some researchers have found an association between breast cancer and specific chemical pesticides, although others have failed to confirm this link.

Environmental epidemiologist Dr. Jeff Baubier, from the USEPA, reported on agricultural regions in Illinois where increased use of the triazine herbicide atrazine has resulted in detectable levels of this pesticide in the groundwater. Rising rates of breast cancer were detected in areas with the highest atrazine water levels.

A 1997 publication noted increased rates of breast cancer in Hawaii, particularly in Kunia, Oahu where high levels of the pesticide DBCP were also detected (Allen et al., "Breast cancer and pesticides in Hawaii: The need for further study." EHP: 105, 3:679-683,1997).

Prompted by the concern of womens' groups, particularly on Long Island, NY, further studies of breast cancer and environmental contamination are underway. We will follow-up and present information as it becomes available.

3) Very young children may be more sensitive to carcinogenic chemicals, including pesticides.

Rates of certain cancers are increasing in this population. Infants and children appear predisposed to higher levels of cancer in conjunction with household pesticide exposure. Dr. James Davis listed conditions of pesticide use in or around the home which had been linked to increased rates of brain cancer in very young children. The following associations are listed in order of decreasing degree of scientific significance, measured by Relative Risk (R.R.), as they pertain to childhood brain cancer.

  1. Household use of pesticide bombs during pregnancy R.R. 6.2;
  2. Household use of No Pest Strips R.R. 5.2.;
  3. Treatment of human lice infestations with lindane shampoo (Kwell) R.R. 4.6;
  4. Treatments for termite control R.R. 3;
  5. Use of garden insecticides R.R. 2.6.

A published report of cancer in children under 15 found strong associations between soft tissue sarcomas and pesticide yard treatments (R.R. 4) and between leukemias and use of no pest strips (R.R. 1.7-3) (Leiss, "Home pesticide use and childhood cancer: A case control study." AJPH, 85, 2:249-252,1995).

[Note: In response to a steady increase for two decades in new cases for some cancers among children - 60% in testicular cancer, 50% in one form of bone cancer, 30% in brain cancer and 10% in one form of blood cancer - the EPA has convened a first-ever federal conference addressing the increase in childhood cancer and its possible link to environmental hazards. At a September, 1997 EPA conference, experts speaking on the special vulnerability of children were charged with recommending research into preventive measures for environmental causes of childhood cancer.]

4) Farmers, golf course superintendents, military dogs which had served in Vietnam, children whose parents apply pesticides for a living, and dogs whose homes are located near marshes, all were found to have increased chances of developing various types of cancer.

Farmers in many countries, despite their overall good health, as discussed by Dr. Mary Ward, tend to experience higher rates than the general population for some cancers. These include leukemia, non-Hodgkin's lymphoma (NHL), multiple myeloma, skin cancer, soft-tissue sarcoma, and cancers of the lip, prostate, brain and stomach.

Golf course superintendents who work in an occupation not usually associated with hazardous conditions are linked to higher rates of mortality from non-Hodgkin's lymphoma, brain and prostate cancer in a recently published study (Kross, et al., "Proportionate mortality study of golf course superintendents," AJIM, 29:501-506,1996).

[Note: Of chemical pesticides used on golf courses, RCC found 46% were either suspect, possible or probable carcinogens. For fungicides alone the carcinogenic rate was 58%. This analysis was based on data from an EPA chart from July of 1996, and pesticide information in the Basic Guide to Pesticides.]

Children of farm workers with life-threatening cancers were described by Dr. Marian Moses. These innocents from two California communities where clusters of cases appeared were predisposed to higher levels of brain cancer, neuroblastoma, leukemia, Wilms tumor (a common childhood malignancy of the kidney) and others. One explanation for the elevated cancer level was their parents' association with pesticides. A study from Shanghai found an association between the mothers' exposure to pesticides during pregnancy and childhood leukemia. In addition, children born in rural areas were found to be at higher risk for leukemia. (Shu, et al., "A population-based case-control study of childhood leukemia in Shanghai," Cancer, 635-644,1988). A report from Brazil has found that Wilm's Tumor could be associated with exposure of either parent, of the fetus in utero or of very young children to pesticides (Sharpe, et al., "Parental exposures to pesticides and risk of Wilms' Tumor in Brazil," AmJE pi, 141, 3:210-217,1995).

Pet dogs whose homes were located near marsh areas (where presumably spraying with pesticides for mosquitoes occurred), and with the two additional risk factors of obesity and being dipped for skin parasites more than twice yearly, were at a significantly greater risk for cancer. These dogs, according to a study (Glickman et al., "Epidemiologic study of insecticide exposures, obesity and risk of bladder cancer in household dogs," J.Tox and Env.Health, 28:407-414,1989) described by Dr. John Reif, were found to have a 30 times greater risk of developing bladder cancer than did pets in the general population.

Military dogs which had served in Vietnam, according to data from Dr. Howard Hayes of NCI, had a higher risk of testicular cancer than military dogs stationed elsewhere. This was thought to be related to pesticide and antibiotic exposure.

5) Animals in which pesticide exposure has been linked to higher cancer rates may indicate an increased risk to humans sharing their environment.

A study of canine malignant lymphoma patients, showed them to be 30% more likely to have lived in a home where the owners had applied 2,4-D or employed a commercial lawn care company to treat their yard. The risk of lymphoma rose when the owners used four or more yearly applications of the herbicide, and a statistically significant trend was found for the number of applications. (Hayes, et al., "Case-control study of canine malignant lymphoma: Positive association with dog owners' use of 2,4-dichlorophenoxyacetic acid herbicides," JNCI, 1226-1231,1991)

Dr. John Harshbarger discussed a notable increase in genital tumors for women and, at the same time, for soft shell clams on the coast of Maine where high herbicide exposure had occurred. Cancer of fish is an excellent sentinel for concentrations of some chemical carcinogens in the environment. A few such sentinel associations have been made with carcinogenic pesticides but more work needs to be done. For example, both soldiers and military dogs who served in Vietnam appear to have increased risk of testicular cancer.

6) Dioxin from various sources, including pesticides, continues to pose a danger. The dioxin body burden of the average American is very close to the level that causes harm.

Dr. Beverly Paigen discussed dioxin, or TCDD, a known contaminant of the chlorophenoxy pesticides, particularly 2,4-D. In addition to being produced by incineration, it is generated when paper is bleached with chlorine. Dioxin is an 'indirect' carcinogen. At a body burden of 7 nanograms/ kilogram, dioxin is known to cause increased susceptibility to viruses and an altered immune response in two species of experimental animals. The average American, with a dioxin body burden of 5-9 nanograms/kilogram, "...is very close to or at the level that causes harm.... Another way of expressing this is that the average person is 'almost full' and further increases in dioxin will be harmful." How a decreased immune response affects carcinogenicity needs further study.

In July, 1997 Dr. Paigen provided a dioxin update. The good news: In Maine a bill was passed making it one of the first states to require companies to reduce the chlorine levels used for bleaching paper. The bad news: A bill requiring a non-chlorine method of paper bleaching was defeated.

Most Conference speakers stressed the need for cancer prevention. This view received additional support from the May 29, 1997 article in the New England Journal of Medicine, "Cancer Undefeated" by Dr. John Bailar, III. Age-adjusted mortality due to cancer in 1994 was 6 percent higher than the rate in 1970, leading Dr. Bailar to conclude that the war against cancer is far from over. Dr. Bailar is calling for "...a national commitment to prevention, with a concomitant rebalancing of the focus and funding of research."

What can we do?

Reliance on labeling for identifying carcinogenic pesticides is not possible.

Pesticide product labels usually do not include such data. Most food labels do not now indicate when carcinogenic or any other specific pesticide residues may be present. This, and the widespread use of chemicals in agriculture, obliges consumers to buy organic as one way to prevent contact with carcinogenic residues. RCC is always available for consultation on particular carcinogen questions and suggestions for less toxic alternatives.

To demonstrate: An organic lunch was served at the Conference. Although providing non-pesticide-treated food was a financial consideration for our organization, we are glad that we made the decision to do so and continue to be gratified by participants' responses. In addition, it served as a reminder that pesticide exposure can be reduced by each individual consumer while shopping.

Rachel Carson was the subject of a 1962 Life Magazine article in which she gave advice we still should heed: "Trusting so-called authority is not enough. A sense of personal responsibility is what we desperately need."

[Note: The Food Quality Protection Act (FQPA), passed in 1996, will, we are told, lead to the eventual withdrawal of carcinogenic pesticides. Until this takes place, the Act permits exposure to "negligible risk" carcinogenic residues in food. Interestingly, the Delaney Clause, which was in place before Silent Spring's publication, had called for zero tolerance for pesticide residues in food, and was abolished with enactment of the FQPA. Under the FQPA, the EPA will give more attention to the effects of pesticides on children, but this will not be done immediately. While we applaud the EPA effort, consumers still need to exercise personal responsibility while waiting for the regulations to work, and hoping that they will.]

Due to space constraints we couldn't provide each speaker's presentation but individual copies are available and a few Conference Proceedings books can still be purchased for $15.00. Specific references are given when they are other than the conference presentations. Please feel free to contact RCC with any questions.

~ Dr. Diana Post, Executive Director

Glossary term:

Relative risk is the increased chance of getting the cancer over 1 (the reference or normal cancer rate). Relative risk compares a test population or person with the control population or person. A relative risk of 1 means that the exposed person is not at any increased cancer risk compared to the control or unexposed person. A relative risk of 2 means that an exposed person is twice as likely to get cancer as an unexposed person. A relative risk of 4.0 with a 95% confidence range of 3-5 is a very significant risk and can not be explained away by chance. However, the same relative risk of 4.0 with a 95% confidence range (or interval) of 0.5-7.5 is not very convincing because the range includes a risk of 1.0, which means no increased risk. Therefore, such a relative risk is said to be non-significant or, to express it another way, the result could have occurred by chance.