Recently, there have been some articles in the press about levels of lead in eggs from urban chicken flocks. Eggs in New York City were tested, and some had relatively high levels of lead. Source: Worries about lead for New York’s garden fresh eggs. This problem is not specific to New York City, as I have heard reports of lead in eggs from hens in other cities, including Madison.
The source of lead is likely the soil, as soil tests have shown higher than normal lead levels as well. This lead may come from lead paints used in the past, manufacturing residues, and/or exhaust fumes from leaded automotive fuels, or possibly from other sources.
In one published article a small flock of hens was observed eating paint chips from a barn. One showed symptoms of lead poisoning (including ataxia and central nervous system dysfunction), but others did not. Their eggs contained fairly high levels of lead. Other than this study, very little research has been published on this topic. Source: (Lead contamination of chicken eggs and tissues from a small farm flock, Trampel, et al., Journal of Veterinary Diagnostic Investigation September 2003 vol. 15 no. 5 418-422.
In the research, and in the New York City case, lead was not detected in the whites of the eggs. Yolks (and shells) were shown to contain lead.
One concern is that ingested lead is deposited in the bones, and then slowly leaches out, so it can be a long-term problem, and one that is not easily corrected. Even if the chickens are removed from the source of lead, they may continue to deposit lead in their eggs for a long time.
So, what should an urban chicken owner do? (more…)