Pesticides and Cancer, Glyphosate and Gut Bugs

Spraying pesticides in Glen Canyon March 2013At the recent “Save the Forests!” meeting, physician Dr Morley Singer told us about an article in the journal of the American Cancer Society that showed links between pesticide use and increased cancer risk. The article is in CA: A Cancer Journal for Clinicians, which is peer-reviewed and highly respected, and he sent us the link.

[HERE’s the link to the article:  Increased cancer burden among pesticide applicators and others due to pesticide exposure.]

What caught our eye was glyphosate, the active ingredient in Aquamaster and Roundup,   and the pesticide most used by SF Rec & Parks’ Natural Areas Program (NAP). Glyphosate is associated with Non Hodgkin Lymphoma. (The whole paper, which is in the public domain, is here as a PDF:  American Cancer Journal – pesticides 2013)


Pesticides increase the risk of cancer not only for the people who apply these toxins, but also for bystanders.  And it’s not just insecticides, also herbicides, which are much more broadly used. From the abstract:

“A growing number of … studies provide substantial evidence that the pesticidesare associated with excess cancer risk. This risk is associated both with those applying the pesticide and, under some conditions, those who are simply bystanders to the application.”

Three of the Four on Mt Davidson

Three of the Four on Mt Davidson

The problem with determining cancer risk from pesticides is that you can’t conduct experiments on people. Experiments on animals would have to be quite long term, and thus expensive.

What you can collect is “epidemiological” evidence – that shows a link between the pesticide and types of cancer (or other conditions), but doesn’t specify how it works. You can also do studies on cells in laboratories, a process that is cheaper (and, frankly, more humane) than doing large experiments on live animals. Those can provide insights to how exactly the toxins work.  Epidemiological evidence is the kind of  evidence that eventually tied cigarette-smoking to lung cancer. The tobacco industry argued that there was no toxicological evidence, but the epidemiological evidence eventually became overwhelming.

As the journal article says: “The use of cultured animal and human cells allows high-throughput assays of pesticide toxicity to be assessed at much lower cost compared with whole-animal studies and without the ethical constraints that limit human studies.”

What the authors did was look at a whole lot of other studies for associations between many types of cancer and many different pesticides. They found a problem.

“In this article, the epidemiological, molecular biology, and toxicological evidence emerging from recent literature assessing the link between specific pesticides and several cancers including prostate cancer, non-Hodgkin lymphoma, leukemia, multiple myeloma, and breast cancer are integrated. Although the review is not exhaustive in its scope or depth, the literature does strongly suggest that the public health problem is real.”


One of the pesticides mentioned was glyphosate, the active ingredient of Roundup and Aquamaster. It’s one the pesticides NAP uses most frequently. (In the graphs below, Roundup/ Aquamaster is represented by the olive-green section at the bottom of each column.)

It’s associated with Non Hodgkin Lymphoma, a group of cancers starting from the lymph nodes.

pesticide use number n vol 2008 to 2012


An article at suggests the growing evidence against glyphosate, possibly the world’s most widely used herbicide: ‘Once called “safer than aspirin,” glyphosate’s reputation for safety isn’t holding up to the scrutiny of independent research. More and more non-industry-funded scientists are finding links between the chemical and all sorts of problems, including cell death, birth defects, miscarriage, low sperm counts, DNA damage, and more recently, destruction of gut bacteria.’

Researchers found that glyphosate residues on food interfere with certain enzymes, with the result that  “…glyphosate enhances the damaging effects of other food borne chemical residues and environmental toxins. Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body.”

[That paper, published this month in the journal Entropy, is HERE.]

It suggests that glyphosate might be causing a lot of the health problems that have been associated with Western diets – including “obesity, diabetes, heart disease, depression, autism, infertility, cancer and Alzheimer’s disease.”


Some countries have already moved to limit pesticide use. According to the CA journal article:

“Rather than wait for human carcinogens to be identified, several European countries, including Sweden, Denmark, the Netherlands, and others, have initiated pesticide use reduction policies that have resulted in substantially diminished pesticide use overall. In the United States, a nationwide use reduction policy has met with resistance politically…”

In San Francisco,  the SF Department of the Environment (SF DOE) regulates pesticide use on any city-owned property – including the Natural Areas. It divides permitted pesticides into three Tiers, with Tier III being the least hazardous, Tier II being more hazardous, and Tier I being the most hazardous.

Right now, glyphosate is classified at Tier II. We asked them to consider reclassifying it as Tier I on the basis of the article in the American Cancer Society journal, and the possibility that glyphosate is an endocrine disruptor. SF DOE refused.

Meanwhile, as the graphs above show, NAP’s use of herbicides has been growing, no matter how you calculate it.  We ask that the Natural Areas Program stop using any Tier I or Tier II chemicals in the Natural Areas. Many of these areas are on high ground. Residues could move downhill into residential areas. They are open spaces where people – including kids – wander, where pets explore, and wildlife lives.  The health risks to everyone are not worth the questionable victories against plants NAP dislikes.

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7 Responses to Pesticides and Cancer, Glyphosate and Gut Bugs

  1. Tony Holiday says:

    I’d force them to stop using pesticides entirely. Cut back the plants, like the blackberries, if you must clear the trails but don’t go around poisoning everything where people and animals go.

  2. Philip Snyder says:

    For my last 4 years as a SF Health Inspector, I worked in the Monitoring Wells Division. Our Major Task was to protect the integrity of the underground aquifer which is slated to become a major source of SF drinking water. When I realized that agencies are splashing hazardous chemicals on the highest portions of SF leaving them to wash down the hills and percolate into the groundwater beneath the City, I became very concerned. Also, since these hills consist of rock layers that are surely fractured the problem becomes even greater. Contaminated water can run down the fractures to very low levels. This is how an artesian well is created. There is no way of knowing how far down the contaminated water may travel. It is possible that it may travel below the protective layers of clay which shield the deep aquifers thus contaminating the very aquifers that the City is trying to protect. Government is a curious institution. Often the left hand doesn’t know what the right hand is doing.

    Philip Snyder

  3. Pingback: People Overwhelmingly Favor Preserving Mount Sutro Forest | Save Mount Sutro Forest

  4. LJ Speakup says:

    Shouldn’t there be a path of legal action in which citizens can sue the city to stop applying these pesticides?

    [Webmaster: It’s not illegal to use them… but if enough people tell the Department of the Environment and the Mayor’s Office and the Board of Supervisors that they don’t want pesticides in the Natural Areas, perhaps they will stop.]

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  7. Pingback: World Health Organization: Roundup “Probably Carcinogenic” | San Francisco Forest Alliance

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