Chicken keeping is all the rage among urbanites interested in affordable, local food, but the eggs may be less wholesome than they presume. Lead, a potent neurotoxin that is especially harmful to young children, commonly contaminates city soils, and urban chickens can pass it into their eggs, researchers report in Environmental Geochemistry and Health. Nearly half the eggs the team collected from chickens raised in New York City community gardens contained detectable levels of lead, whereas none of the store-bought eggs did, and the degree of contamination tracked that of the soil where the chickens lived. So just how dangerous are urban eggs? While no safety standards specifically govern lead in eggs, all but one of the city eggs that the researchers tested had concentrations deemed acceptable for other foods—good news. Still, the researchers estimated that eating an egg a day with the highest lead concentration they found, 167 parts per billion (ppb), could increase kids’ blood lead levels by an amount linked to a loss of roughly one IQ point. And eggs could easily become even more contaminated: Those they tested came from chickens living on soil that maxed out at about 600 ppm of lead, but levels greater than 1000 ppm are common in some cities. Fortunately, urban farmers who prefer their eggs unleaded can take action, including adding clean soil to chicken runs and giving calcium supplements to their flock.
*Correction, 13 December, 11 a.m.: This item has been corrected. The figure 167 parts per million has been changed to 167 parts per billion. Science regrets the error.