Natural Areas Pesticides: The Fearsome Four

Three of the Four on Mt Davidson

The Natural Areas Program (NAP) uses four herbicides classified as “Most Hazardous” (Tier I) or “More Hazardous” (Tier II) by San Francisco’s Department of the Environment (DoE):

  • Garlon 4 Ultra (triclopyr)
  • Roundup or Aquamaster (glyphosate)
  • Polaris or Habitat (imazapyr)
  • Milestone (aminopyralid)

All these chemicals have serious problems: they’re associated with birth-defects and pregnancy failures; they’re endocrine disruptors; they poison animals, especially amphibians but also reduce bird-nesting success; and/or they’re persistent – they stick around.

For details of the risks associated with each one, read the article Natural Areas Program’s Pesticides: Toxic and Toxic-er.

We often get questions about this, especially from people who have heard about NAP from its supporters.

Source: (derived from from SF City records)

Q:  They hardly ever use pesticides, right? Just once every few years?

A:  NAP applied pesticides 86 times in 2011, up from 71 the year before. (We’re relying on City records here. There may be gaps.)

Q: But maybe they used less in each application?

A: The amounts used went up in proportion.

Q: Don’t they use very small amounts? Doesn’t the dose makes the poison?

A: In 2010, NAP used more Tier I herbicides than any comparable park department. (We don’t have compiled data for 2011 for other parks departments.)  Anyway, “the dose makes the poison” isn’t always true. Here’s what the American Chemical Society said in its Public Policy Statement, Testing for Endocrine Disruption:

Endocrine disruption is the alteration of the endocrine system that causes adverse health effects in an intact organism, or its progeny, or (sub)populations. Endocrine hormones naturally act at ultra-low concentrations and certain chemicals are suspected of altering endocrine function at similarly low concentrations, which sometime occur in the environment. A large and growing body of environmental health literature shows that endocrine disrupting substances have complicated dose-response curves that do not fit the central tenet of regulatory toxicology, namely, that the ‘dose makes the poison.’

Q: But aren’t they herbicides… don’t they act only on plants?

A:  They act differently on plants and on animals, but they still can – and do – impact animals (and people).  They may use different bio-chemical pathways in animals and in plants, and thus have different effects. None of these effects is good. The city of San Francisco subscribes to the “Precautionary Principle” – if you don’t know the effects, don’t use it. The natural areas are where children explore, people walk, and pets are exercised. This is not a risk they should take.