Heavy Metal Exposure in Birds
Panic Over Paint, Toys, and Parrot Cages
The first case of zinc toxicity that I ever saw occurred in my practice in New Jersey involved an adorable yellow-naped Amazon named “Monty”. He was an absolute delight, bright and alert, in perfect feather, but he had a very perplexing problem. He regularly regurgitated part of his meals each evening, and he had an odd pink tint to the white portion of his droppings. He had already been seen by several other veterinarians and he had even been tested for lead poisoning (the pink colour of the droppings is often suggestive) but the test results were negative. At that time, zinc toxicity was not well recognized, but the owner mentioned she had been worried about a problem with the cage as it was not from a well known manufacturer, and the bird had removed some of the paint from the bars. Having just heard about zinc toxicity, we immediately pulled some blood for additional tests and started the bird on “chelators” which help remove the zinc from the birds system. Not only did Monty improve on the medication, but blood tests confirmed high zinc blood levels. Unfortunately, some controversy exists over what is diagnostic in the way of blood results and what might be normal exposure. In general, serum levels of over 3 ppm (30 ug/dl) in combination with clinical signs of heavy metal exposure are suggestive of zinc poisoning. Although much publicity has lately focused on a possible link between zinc exposure and feather mutilation disorders, at this point those conclusions may be somewhat premature. Studies suggesting a connection between zinc and feather problems remain controversial in the veterinary community. However, having serum zinc levels checked when other diagnostic avenues have been exhausted may not be unreasonable, at least until such time as the relationship is better defined.
This may obviously damage the cage, although if there is a portion which can be removed such as a handle or a ladder or a grill – anything coated in the same paint or finish that is not essential to the cage, then this can be sent to a toxicology laboratory by your veterinarian for testing. Modern powder coatings will usually show zinc levels of 0.00290% or less (less than 29 parts per million). Powder coatings are simply a type of paint that is applied to most modern bird cages. Instead of being sprayed on, the powder is melted on to the wire during heating, and for a variety of reasons this results in less harm to the environment than is produced during old fashioned spray-painting (or brass finishing) of bird cage wire. As a manufacturer of bird cages in North America, our company gets lots of questions about the coatings underneath the powder coating (ie on the steel wire) as well as the zinc and lead content of the new powder coatings, along with the new metallic looking ultra-thin finishes. The steel wire we use is not treated with any substance containing appreciable amounts of either lead or zinc. Some of the new finishes are only a few microns thick (thus showing the metallic nature of the wire underneath) but contain no metals at all.
Where to get answers?
Ask your pet retailer to check with your cage manufacturer if you have any questions about either zinc or lead content in the paint. Just remember that cage paint is rarely a source of heavy metal exposure in a recently manufactured North American cage. It actually takes a lot of paint to expose the birds to significant amounts of metals in most cases. For example, even for a parrot cage containing 3000 ppm (0.3 %) lead, it would take ingestion of most of the paint on the cage for the average parrot to show any clinical signs of lead exposure. In the old days, lead paint may have contained as much as 30 or 40% lead – thankfully these paints are no longer available. Lead poisoning in this day and age is usually related to stained glass ornaments, lead shot, lead curtain weights, and lead foil. Welded wire used in bird aviaries, and toys containing galvanized metal parts are the most common sources of significant zinc exposure. Brass finishes – although now discontinued by many North American manufacturers for environmental reasons – do contain trace amounts of zinc, but certainly not enough to cause clinical signs of zinc exposure in any bird. Brass finishes do not contain lead.
Check with your cage manufacturer and your veterinarian if you have any questions about heavy metal exposure – it is always better to prevent such problems than to treat them!
Louise Bauck BSc, DVM, MVSc.