Lead Contamination of Chicken Eggs and Tissues from a Small Farm Flock

Abstract

Abstract. Twenty mixed-breed adult laying hens from a small farm flock in Iowa were clinically normal but had been exposed to chips of lead-based paint in their environment. These chickens were brought to the Iowa State University Veterinary Diagnostic Laboratory, Ames, Iowa, where the concentration of lead in blood, eggs (yolk, albumen, and shell), and tissues (liver, kidney, muscle, and ovary) from 5 selected chickens was determined over a period of 9 days. Blood lead levels ranged from less than 50 to 760 ppb. Lead contamination of the yolks varied from less than 20 to 400 ppb, and shells were found to contain up to 450 ppb lead. Albumen contained no detectable amount. Lead content of the egg yolks strongly correlated with blood lead levels. Deposition of lead in the shells did not correlate well with blood lead levels. Mean tissue lead accumulation was highest in kidneys (1,360 ppb), with livers ranking second (500 ppb) and ovarian tissue third (320 ppb). Muscle contained the lowest level of lead (280 ppb). Lead contamination of egg yolks and edible chicken tissues represents a potential public health hazard, especially to children repeatedly consuming eggs from contaminated family-owned flocks.

Lead Exposure from Backyard Chicken Eggs: A Public Health Risk?

“…This is consistent with prior reports of lead toxicosis in chickens [13,14]. Following the ingestion of lead, there are dose-related increases in the blood, kidney, liver, and bone [15].…”

“…The lead levels detected in the edible portion in this case were quite variable ranging from non-detectable to as high as 0.97 μg/g. A 2003 study on lead contamination in a small Iowa farm flock of chickens exposed to lead-based paint chips found a strong correlation between blood lead levels and the lead content of egg yolks [14]. In this case study, we could not determine the relationship between the concentration of lead in the blood and lead levels found in eggs, as the chicken of origin for each egg submitted was unknown.…”

“…Lead was not detected in the breast or thigh muscle of the chickens submitted for analysis despite the detection of high concentrations of lead in the blood and other tissues. Some studies have reported high concentrations of lead in the muscle [14], whereas others have reported very low to non-detectable levels [17,18]. The variability in finding a detectable amount of lead in the muscle tissue could be due to individual genetic differences in the metabolism and distribution of lead, dietary influence, length of exposure, or timing of sample collection.…”

“…Eggs accumulate lead in the shell as well as in the edible portion [14,20]. Previous studies have reported that little to no lead can be detected in the albumen, while the yolk often contains much higher concentrations of lead [14,17,20].…”

“…Previous studies have reported that little to no lead can be detected in the albumen, while the yolk often contains much higher concentrations of lead [14,17,20]. We chose to combine the yolk and albumen for lead analysis in order to more closely simulate consumer exposure such as eating an egg for breakfast.…”