07
Aug
28 Pesticides Linked to Mammary Gland Cancer, Inadequately Reviewed by EPA
(Beyond Pesticides, August 7, 2020) Research out of the Silent Spring Institute identifies 28 registered pesticides linked with development of mammary gland tumors in animal studies. Study authors Bethsaida Cardona and Ruthann Rudel also report that many of the pesticides they investigated behave as endocrine disruptors; breast cancers in humans are significantly influenced by hormones generated by the endocrine system. The Environmental Protection Agency (EPA) acknowledges that nine of these 28 pesticide compounds cause mammary tumors, but dismisses the evidence of the other 19. The results of this research, published in the journal Molecular and Cellular Endocrinology, evince Beyond Pesticides’ long-standing argument that the risk assessment process used by EPA for its pesticide registration process is substantially inadequate to protect human health.
The co-authors cite, as the catalyst for this research project, a Cape Cod resident’s outreach to the Silent Spring Institute several years ago, asking for information about the herbicide triclopyr because utility companies wanted to spray it on vegetation below local power lines. (The compound has also been used by the logging industry in the Pacific Northwest.) They reviewed more than 400 EPA pesticide documents on the health impacts of many registered pesticides for this research, conducted as part of Silent Spring Institute’s Safer Chemicals Program, which is “developing new cost-effective ways of screening chemicals for their effects on the breast.”
Researcher Ruthann Rudel, MS, an environmental toxicologist and director of research at the institute, notes, “We know pesticides like DDT increase breast cancer risk, so we decided to look into it. After examining pesticide registration documents from EPA, we found two separate studies in which rodents developed mammary gland tumors after being exposed to triclopyr, yet for some reason regulators dismissed the information in their decision not to treat it as a carcinogen.” (It is long established that people exposed to DDT during childhood are at increased risk of developing breast cancer.)
The researchers hypothesized that effects on mammary gland development have been inadequately considered by EPA in its review of animal studies related to pesticide impacts, and that mammary gland tumor development has been improperly dismissed from consideration in the registration process. Ms. Rudel and Ms. Cardona identified 35 different pesticides that impact mammary glands, with some of the endpoints being tumors. The researchers note, in their paper, that 24 of the 35 pesticides that affect mammary gland endpoints are still found in products approved for use in the U.S.
In considering registration of a pesticide, EPA is required — by authorization via FIFRA, the Federal Insecticide, Fungicide, and Rodenticide Act — to evaluate risks to human and ecological health. The consideration of potential impacts to human health includes review of both acute toxicity (from a single exposure to a pesticide), and effects of chronic exposure over time. EPA is also supposed to evaluate the carcinogenicity of exposure to pesticides; it ultimately assigns one of the following classifications to any considered pesticide: (1) Carcinogenic to Humans, (2) Likely to be Carcinogenic to Humans, (3) Suggestive Evidence of Carcinogenic Potential, (4) Inadequate Information to Assess Carcinogenic Potential, or (5) Not Likely to be Carcinogenic to Humans.
Toxicological assessment typically evaluates one chemical at a time, and in terms of cancer risks, looks primarily at a chemical’s ability to cause damage to DNA. The researchers note, however, that “recent findings in cancer biology show there are many ways chemicals can trigger the development of cancer. For example, chemicals can suppress the immune system, cause chronic inflammation, or disrupt the body’s system of hormones, all of which can lead to the growth of breast [and other kinds of] tumors.”
They write, in their July 2020 paper on the subject study, “It has been previously reported that chemically induced effects on the mammary gland are not assessed in the types of guideline toxicology studies required for pesticide registration, and that when mammary tumors are observed in two-year rodent cancer bioassays they are often dismissed and not carried forward into risk assessments. Some of these decisions may reflect limited appreciation for the interaction of endocrine pathways in breast carcinogenesis.”
Indeed, Silent Spring Institute published another study, in May 2020, that set out a map of the multiple pathways through which environmental chemicals, such as pesticides, can trigger the development of breast cancer. Having used ionizing radiation as a model trigger, co-authors Ruthann Rudel and Jessica Helm suggest that their findings can be generalized to other environmental carcinogens and thus, help regulators identify compounds that increase breast cancer risk.
Ms. Rudel commented, in that earlier 2020 paper, “We know exposure to toxic chemicals can play an important role in the development of breast cancer. Yet, when regulators try to evaluate whether a chemical is harmful or not, the tests they use do not capture the effects on the breast. This gap in testing means potential breast carcinogens are being given the green light for use.”
This recent study brings renewed attention to EPA’s failures in assessing threats to human health from pesticide use. The researchers assert that EPA ignored the cancer risks that these 28 pesticides pose, and that the evidence on which the agency bases its registrations of pesticides should include examination of compounds’ impacts on mammary gland development, and their endocrine disrupting activity.
The study co-authors also recommend that five compounds — because of their extensive use and their potential harms, as evidenced through the study’s analysis — be re-evaluated by EPA: triclopyr, IPBC (3-Iodo-2-propynyl butylcarbamate, a common “inert” ingredient of glyphosate herbicides), malathion, atrazine, and propylene oxide. Triclopyr is an herbicide used in agriculture and to control vegetation along rights-of-way; IPBC is a preservative in cosmetics; malathion is a common residential and agricultural insecticide that is also used in some lice treatments; atrazine is a frequently used agricultural herbicide; and propylene oxide is a preservative used for cosmetics, pharmaceuticals, and food (and has many similarities to ethylene oxide, a known human carcinogen).
The Center for Biological Diversity has also charged that EPA pesticide risk assessment relies far too heavily on industry-produced (and funded) studies to inform its conclusions, and sometimes ignores its own guidelines, never mind scientific evidence, for assessing pesticide risks. A recent example of EPA’s contravention of scientific evidence was its 2019 decision to issue an interim re-registration of glyphosate, which has been repeatedly linked to the development of non-Hodgkin Lymphoma (and other cancers). It did so in the face of widespread consensus among scientists, including findings, by its own Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry, supporting the carcinogenicity of glyphosate. Another recent example is EPA’s spring 2020 registration of a demonstrably carcinogenic herbicide, isoxaflutole — a compound listed by EPA as “likely to be carcinogenic” to humans.
These examples, and the inattention to links between pesticides and mammary gland tumor development revealed by the Silent Spring Institute study, are but a few instances of EPA’s “dereliction of duty” during the Trump administration, as the agency has increasingly moved away from the scientific integrity that is supposed to anchor its mission to protect human and environmental health, and toward the agendas of corporate actors, such as the pesticide industry. Beyond Pesticides covered evidence of the erosion of this integrity, which was summarized in a report by the EPA Office of the Inspector General (OIG) in May 2020. The OIG report found that “400 EPA employees had experienced, but did not report, potential violations of EPA’s scientific integrity policy. Further, according to OIG’s findings, dissatisfaction regarding scientific integrity abounds within the agency.”
Beyond Pesticides has repeatedly identified this trend at EPA, and taken many actions to attempt to counter it, including a January 2020 letter to EPA Administrator Andrew Wheeler, insisting that EPA do the fundamental job with which it has been tasked: use the best science to protect the public and the environment. The letter said: “A top panel of government-appointed scientists, many of them hand-selected by the Trump administration, said on Tuesday that three of President Trump’s most far-reaching and scrutinized proposals to weaken major environmental regulations are at odds with established science.”
In light of the current status of EPA function, the public can take steps to protect human health. Chief among those is to use organic foods and products when at all possible, and to assess products used in the home, garden, and local community for safety. Beyond Pesticides has many resources to help individuals and communities be safer and healthier: check out the website pages on organic agriculture, pesticide alternatives, lawns and landscapes, and children and schools, among others. For more information on the relationships between pesticides and human disease, explore Beyond Pesticides’ Pesticide-Induced Diseases Database.
Sources: https://silentspring.org/news/dozens-pesticides-linked-mammary-gland-tumors-animal-studies and https://www.sciencedirect.com/science/article/pii/S0303720720302276
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
