Unfortunately, some controversy exists over what is diagnostic in the way of blood results and what might be normal exposure. 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.
Powder coatings are simply a type of paint that is applied to most modern bird cages.
The steel wire we use is not treated with any substance containing appreciable amounts of either lead or zinc. 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. Lead poisoning in this day and age is usually related to stained glass ornaments, lead shot, lead curtain weights, and lead foil.