Date: 3/11/18 10:15 am
From: Dan Gleason <dan-gleason...>
Subject: [obol] Re: Birds and Sluggo

> Hi there,
> Does anyone know the effect of iron phosphate-based slug bait on
> birds? I recently noticed Sluggo was gone from one place I had put it
> but not gone everywhere else. I put more out and binned a towhee
> eating granule after granule before I chased it off and awkwardly
> picked the rest up. The package says its wildlife safe...
> Thanks

This question from one of my customers a couple of years ago. I looked into this matter and in my opinion, it may not be safe for wildlife as it states. My explanation (long) is below

Dan Gleason

Evaluation of safety (or not) of Iron phosphate slug bait near bird feeding stations

March 4, 2016; Opinion by Dan Gleason, Co-owner of Wild Birds Unlimited

After a review of some literature and consideration of documents from US and other countries, I would recommend against using any slug bait containing iron phosphate, at least in areas where birds might be feeding and accidentally ingest it. There is a possibility that birds could be harmed although there is not a high probability of this happening.

The explanation is not a simple one.

Slug bait manufacturers can get away with labelling their iron phosphate based product as "safe" and "natural" because both are true—iron phosphate does occur in nature and it is harmless by itself, passing through the digestive system unaltered with no effect on the body. Because of this, the EPA simply says that it is safe and no additional testing is required. Since it is harmless, a child could eat a handful without harm and pets could harmlessly eat it. Sounds perfect, right?

So what's the problem? The problem is that iron phosphate alone is harmless—to people, to cats and dogs, to birds, AND to slugs. Like all other animals, slugs are able to eat as much iron phosphate as they can with no harm whatsoever. Yet, studies show Sluggo and other such baits are highly effective at killing slugs.

Why? The answer to this enigma lies with the "inert" ingredients, which, in the United States, are not required to be listed. Australia, however, does require inert ingredients to be listed. From information I looked at, it appears that these baits work because a chemical called EDTA (Ethylenediaminetetraacetic acid) is added. This is one of the "inert" ingredients.

By itself, EDTA is not a problem, but it is a strong chelating agent. Alone, iron phosphate passes through the digestive system intact, but in the presence of EDTA, the iron is released into the intestine and the iron accumulates in the eater’s tissues, eventually resulting in iron-poisoning… which kills the eater, and, in the case of slug bait, usually the slug. Excess iron also kills other animals, including beneficial ones such as earthworms and frogs as well as pets and even humans. Of course, larger animals can tolerate larger amounts of the accumulated iron than do slugs, but it can still very toxic.

If you know about the actions of EDTA, the above paragraph may sound contradictory. EDTA is a strong chelating agent, which means that it can bind heavy metals into a complex that can safely be eliminated from the body. The use of EDTA is a primary treatment for lead-poisoning, because it binds and removes lead ions from the body's tissues. It also can bind up iron and other heavy metals. But in the case of iron, at some point during the digestive process, iron ions bound to EDTA are released into the intestines where they can be absorbed into the body's tissues.

Iron compounds are not easily absorbed by the body and many forms of iron (including iron phosphate) simply pass through the body unchanged, without releasing iron ions. One study, examining possible ways to treat iron deficiency, found that iron, in various forms, combined with wheat flour showed little or no measurable uptake of iron by the intestine. (The wheat flour was used to make chapatis, a form of un-leavened flat-bread.) However, the addition of Na-Fe-EDTA (iron bound with EDTA) increased the ability of the body to absorb iron by 2 to 7 times. Thus, in limited quantities, iron-EDTA can be used to treat iron deficiency, but in high doses, excess iron can be built up causing iron-poisoning. So, iron phosphate in combination with EDTA does make an effective poison.

From the materials I was able to find, iron-poisoning in dogs was extremely rare prior to 2008. But, since the introduction of these slug-type products, several cases have been reported. The number of cases is still very, very small, but the incidence is increasing and most are related to slug bait ingestion. Since iron phosphate is considered harmless there is no USDA requirement to put a bitter tasting compound into the product to repel dogs and other animals. However, this is required in older and more toxic forms of slug bait. Thus, the possibility of iron-poisoning is small, but not zero for pets.

However, the risk may be higher for birds, as they feed on seed and perhaps, in the process, ingest slug bait. Birds’ smaller size and higher metabolism could put them at higher risk.

So, in short, I would discourage the use of such slug baits and consider them as not completely safe to use around bird feeders. Even in places where birds are not feeding, there is the possibility of other animals being poisoned. However, these products (containing iron phosphate) are far less toxic than older types of slug bait.

(Barbara Gleason did successfully use beer in cups placed into the ground so slugs fell in as they went after the beer. They were unable to climb out. She did though need to recover the cups after each night and replace it each evening.)

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