A group of citizens is upset with the city's use of an herbicide known as 2,4-D in a Colorado Springs park that's popular with families and pet owners walking dogs and families.
Nicole Rosa, who lives near the Shooks Run Park, noticed several small yellow signs reading "WARNING: PESTICIDES APPLIED" in the grassy stretch between East Willamette Avenue and East Cache La Poudre Street on the morning of Aug. 25. Four hours later, all of the signs had been removed except one.
"I don't really appreciate my park being poisoned without any kind of advance notice," said Rosa, who has taken her dog on daily walks at the park for 11 years.
An online petition that she since started to ask the city's department of Parks, Recreation and Cultural Services to "use non-toxic alternatives" to pesticides and herbicides has garnered more than 170 signatures.
According to the National Pesticide Information Center, 2,4-dichlorophenoxyacetic acid is a herbicide that kills broadleaf weeds but is harmless to most grasses. The chemical is considered a general use product by the Environmental Protection Agency, meaning it's available to the public in a variety of name-brand weed killers.
Kurt Schroeder, Colorado Springs park operations and development manager, said many of the city's parks are sprayed once or twice annually with 2,4-D or Roundup, a synthetic herbicide brand containing a chemical known as glyphosate.
"They're not restricted chemicals or anything out of the ordinary," Schroeder said. "It's the same chemical that you or I could walk into a store and buy off the shelf."
Other municipalities in Colorado have made changes over the past few years related to herbicide use on city property. In 2011, Boulder decided to stop using Roundup in public spaces due to its toxicity. Under Durango's organically managed parks ordinance, natural alternatives to the pesticides and chemical fertilizers must be used at city parks. Manitou Springs is considering a similar proposal.
Colorado Springs typically contracts herbicide application jobs out to one of several local commercial applicators registered with the state to ensure that the chemicals are handled safely, Schroeder said.
"By going to a certified applicator, we're confident that we're taking all of the steps necessary to ensure that it [the herbicide] is applied appropriately, and the health and safety of our park users is protected," Schroeder said.
But some are concerned that the signs were not left up for a long enough period of time for the sprayed area to be safe for parkgoers and their pets.
"There's young kids and dogs - they're there when the poisons are there, when the poison is still active," said Bruce Hamilton, a resident who has lived near the park for more than three decades.
Once 2,4-D spray has dried on leaves and grasses where it has been applied, the risks associated with exposure are generally believed to be minimal, said Michael Rigirozzi, a pesticide enforcement specialist with the Colorado Department of Agriculture.
"There are a few folks that could have sensitives to it, but that's fairly rare," he said.
According to the pesticide information center, the half-life of 2,4-D is typically 1 to 14 days, meaning it can take up to two weeks for half off the original amount to break down.
The toxicity of 2,4-D to people and animals depends on the form the herbicide takes and the nature of the exposure. People who breath the vapors can experience coughing or dizziness. Ingesting the chemical has been associated with similar symptoms in humans and pets, such as vomiting and diarrhea. People may also experience headaches or feelings of confusion or aggression, according to the center.
"I don't think there's ever a reason to spray [herbicides], but I was just surprised that the city would do this in a space where people often walk their dogs or children play," said Laura van der Pol, who lives about a block from the trail that runs through the park and often walks her dog there.
Commercial pesticide applicators are required to post warning signs specifying the type of chemical used at the time of the application, but there's no rule stipulating how long the signs must remain up.
The application in Shooks Run Park was done by TruGreen Lawn Car, a Memphis, Tenn.-based maintenance service provider. The name of the pesticide was written on the back of the signs, which are five inches long by four inches wide under state requirement, said Ryan Petitti, TruGreen's regional technical manager for Colorado and a handful of other western states.
"It's a little difficult on commercial properties because you have so many people on and off the prop after we're there. Typically, we'd like to see them [the signs] on the property for 24 hours," Petitti said. "After we're there, it's out of our hands, unfortunately."
Under the company's policy, the crews who completed the application also avoided spraying within three feet of Shooks Run Creek, which runs through the park, Petitti said.
The jury is still out on the longterm effects of 2,4-D.
The herbicide was first introduced to the United States in the 1940s. It was one of two ingredients in Agent Orange, a chemical used by the U.S. military in herbicidal warfare during the Vietnam War. The second chemical ingredient, 2,4,5-T, produced harmful by-product known as dioxin, which eventually lead to the EPA's ban on Agent Orange.
Some studies have hinted at a link between 2,4-D exposure and a type of cancer known as Non-Hodgkin lymphoma. The EPA said in 2004 that the chemical could not be classified with regard to its ability to cause cancer, citing lack of research, according to the pesticide information center. In 2015, the World Health Organization's International Agency for Research on Cancer classified 2,4-D as "possibly carcinogenic to humans, based on inadequate evidence in humans and limited evidence in experimental animals."
Betty Ball, coordinator for the Boulder-based nonprofit Rocky Mountain Peace and Justice Center's "Citizens for Pesticide Reform" campaign, said 2,4-D is unsafe to use, especially in public spaces such as parks. Natural alternatives, such as gluten-free corn meal or mixture of water and vinegar, are just as effective in killing broad-leaf weeds, she said.
"That's the problem with most things like this, there hasn't' been enough research to prove that they're unsafe," Ball said. "The city or county should have to prove that it's safe. The public shouldn't have to prove that it's dangerous."
But Thia Walker, a pesticide education specialist with the Colorado State University Extension Service, said chemicals such as 2,4-D have to pass more than 200 tests to be registered by the EPA. Over the past few decades, pesticides and herbicides on the market have become a lot safer than those used 50 years ago, she said.
"We've banned a lot of pesticides that have adverse effects," Walker said. "There's a greater emphasis nowadays that making sure that risk is greatly reduced."