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Low doses of pesticides are also hazardous to our health

May 1, 2012

We are reprinting, with permission, an article on the Save Sutro website about recent research reporting that even low doses of chemicals can be harmful to our health.  This research has serious implications for the pesticides being used by the many “restoration” projects in the San Francisco Bay Area.  This article is focused on pesticide use by San Francisco’s misnamed Natural Areas Program.  In fact, every manager of public land in the Bay Area that engages in native plant “restorations” uses pesticides to eradicate non-native species. 

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When we speak up against the Natural Area Program’s frequent pesticide use, its supporters frequently tell us that – compared with say commercial agriculture – the Natural Areas Program (NAP) uses small amounts of toxic chemicals. “The dose makes the poison,” they argue.

But it’s not true.

For now, we’ll leave aside the question of whether it’s reasonable to compare NAP to  commercial agriculture (where fears of chemicals are driving a growing Organic movement). What we’d like to talk about today is recent research about pesticides, specifically, endocrine disruptors. Here’s a quote from the abstract of a study by a group of scientists:

“For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses….

“…Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses.”

[Ref: Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses, Vandeberg et al, in Endocrine Reviews, March 2012]

WHY WE’RE CONCERNED

The NAP uses several pesticides rated as “Hazardous” or “Most Hazardous” by San Francisco’s Department of the Environment. But the one they’ve favored is glyphosate — better known as Roundup or Aquamaster.

It’s strongly suspected of being an endocrine disruptor.

Here’s a 2009 study: Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines.

Another study, also published in 2009, looked at puberty and testosterone: Prepubertal exposure to commercial formulation of the herbicide glyphosate alters testosterone levels and testicular morphology. The abstract of the study ends with this sentence, “These results suggest that commercial formulation of glyphosate is a potent endocrine disruptor in vivo, causing disturbances in the reproductive development of rats when the exposure was performed during the puberty period.”

And here’s a study published in 2007, reflecting the research of a group of scientists from Texas A&M: Alteration of estrogen-regulated gene expression in human cells induced by the agricultural and horticultural herbicide glyphosate

THE NATURAL AREAS PROGRAM DEFENDS PESTICIDE USE

Most people weren’t aware that pesticides were being used in so-called “Natural Areas.” The notices were small and well below eye-level. You had to be looking for them, which isn’t likely for most people out hiking or jogging by, or keeping an eye on small kids. In recent months, the labeling has improved, with taller posts and clearer information.

Now that people are beginning to notice, they’re also objecting. The response we hear most often is “Why would they use herbicides in a natural area?”

So the NAP has started posting explanations, justifying its use of toxic herbicides justifiable against “invasive plants.”

These plants, they say, are “a handful of non-native species” that are “displacing the rich biodiversity of native flora and degrading our natural heritage.”

WHY WE DISAGREE

We have several problems with this statement.

  • If it’s a “handful,” the NAP must have very big hands. From the pesticide application records, we’ve counted nearly twenty-five different plant species under attack by chemicals — including a couple that aren’t actually non-native.
  • There’s no evidence that all these plants are invasive and that they’re “displacing the rich biodiversity.” Native plants and non-native plants thrive together in natural mixed ecosystems. NAP can never eliminate all the non-native plants; the best it can achieve is a different mix, precariously maintained through intensive gardening.
  • There’s also no evidence it’s working. Using chemicals to kills things is cheap and easy, but it leaves a gap where something else will grow. Given that San Francisco’s environment has changed greatly since the 1776 cut-off used to define “native” plants, it’s not going to be those plants. Rather, what will naturally grow back will be the most invasive plant at the site. An excuse for more herbicides.
  • The NAP is destroying habitat in its quest to kill native plants. Many of the plants destroyed are bushes that provide cover and nesting places, or flowering plants that offer nectar to butterflies, bees and other pollinators and the birds and animals that feed on them. The “native flora” don’t necessarily provide much of either, even if they can be successfully gardened.
One Comment leave one →
  1. Don E permalink
    May 1, 2012 12:02 pm

    I agree with the dot points at the end that using herbicides in the NAP is not justified (there is no such thing as zero risk), the plants they kill are not invasive, there is no evidence it is working (weeds are adapting to herbicides making the effort futile), and NAP is destroying habitat.

    However, this is repeating nonsense about EDCs. That the dose makes the poison is not dogma (religion) but a scientific principle. The Vandenberg article, which reviews the literature, does not disprove the principle. If anyone is worried about low doses of EDCs and believe that “there are no safe doses for endocrine disruptors” they should not eat tofu.

    My BS meter goes off whenever I see words like link, may have, and could have. However, Vandenberg makes a good point that high dose studies may not always predict low dose effects e.g., cell and rat studies like the three others cited. She says that there should be more tests done at the range of human exposures. Studies have been done. Dozens of long-term studies have shown no bad health effects on people who are exposed to these pesticides occupationally.

    Nevertheless, everyone should read the warning labels before they use herbicides and pesticides; they can make you sick. Personally, I always use gloves and a mask when using them.

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