Posted by Deb White on 9/9/2020 to Materials Safety
If one topic can get folks riled up in the chat room about bird toy safety, it would be the topic of zinc.
In this post I would like to add to the conversation and challenge the “conventional wisdom” currently lurking online.
First, a few facts about zinc:
- Zinc is not toxic by nature.
- Zinc is an essential nutrient for the growth and development of birds and is incorporated into avian diets.
- Zinc is found everywhere, in every cell of the human body, in the earth, in our food and in our products.
- Virtually nothing is zinc free.
- The issue with zinc is "dosage” or level of exposure.
It is certainly not my position that zinc poisoning does not occur. Rather, it is my viewpoint that, it is highly improbable that a bird can get zinc poisoning from the type of galvanized hardware commonly used in bird toys by responsible manufacturers.
Galvanization is the process used to treat steel and prevent rusting. Not all methods of galvanization are "equal" when it comes to posing a risk of zinc ingestion. The two main methods of galvanization are hot dip galvanization and electro-galvanization.
Hot dip galvanization is a process where the metal is dipped in a bath of molten zinc. Metal treated in this fashion has a dull, rough, and flaky surface of zinc which does pose a risk of zinc ingestion to birds if chewed.
Electro-galvanization is the process where a very thin (<.0005”), tighter-bonding coat of zinc is applied to metal via electro-deposition. The surfaces of the materials treated by this method are smooth and shiny in comparison to those treated by the hot dip method. In other words, there are no loose and flaky zinc components available for birds to swallow.
How to Tell the Difference
It is often very easy to discern what method was used by visual inspection of the metal as illustrated in the photo below:
The texture of the surface is the most reliable indicator as the degree of “shininess” can vary based on the level of other elements (C, Si, P, and Mo) in the base steel.
Evaluating the Potential Risks
Many avian health specialists have stated that for zinc related health problems to result, a parrot must swallow the metal components and that "beaking" the parts is insufficient for toxicity to develop. Here is the text of an email from Brian Speer, DVM posted online several years ago:
Zinc will dissolve under acidic conditions as would be present in a bird’s digestive system. Therefore, if a bird spent a significant amount of time chewing on toy hardware with a flaky galvanized coating, then it is possible they could ingest enough zinc to build up toxic levels in their system over time. For this reason, hot dipped galvanized hardware should not be used.
Metals treated by the electro-galvanization procedure have a very tightly bonded layer of zinc that will not flake and therefore will not pose a risk of zinc ingestion unless the metal object can be swallowed in its entirety. It should also be noted that a bird’s saliva is neutral in pH and therefore mouth contact with a non-flaky galvanized surface will not result in the leaching of zinc. Our parrots simply aren’t going to swallow a several inch-long piece of wire or a 2” washer in its entirety.
But Wouldn’t it Be Safer to Use Stainless Steel?
Maybe, maybe not. I will agree stainless steel components are the safest hardware alternative. But, given the above arguments and facts is the 4-5x cost increase necessary? This decision is entirely up to the individual bird owner based on their knowledge of an individual bird and how they interact with toys.
My belief is that bird owners can safely proceed by taking a balanced, common sense approach using these three guidelines:
- Never use hardware that has been treated by the hot dip method.
- Toy parts should not be galvanized by any method if they are of a size that potentially could be swallowed in their entirety. For small toy parts, either nickel-plated or stainless-steel options should be used.
- Electro-galvanized hardware is acceptable if the components are too large to be ingested.