Lead in New York City community garden chicken eggs: influential factors and health implications

Raising chickens for eggs in urban areas is becoming increasingly common. Urban chickens may be exposed to lead, a common urban soil contaminant. We measured lead concentrations in chicken eggs from New York City (NYC) community gardens and collected information on factors that might affect those concentrations. Lead was detected between 10 and 167 μg/kg in 48 % of NYC eggs. Measures of lead in eggs from a henhouse were significantly associated (p < 0.005) with lead concentrations in soil. The association between soil and egg lead has been evaluated only once before, by a study of a rural region in Belgium. In our study, the apparent lead soil-to-egg transfer efficiency was considerably lower than that found in Belgium, suggesting that there may be important geographic differences in this transfer. We developed models that suggested that, for sites like ours, lead concentrations in >50 % of eggs from a henhouse would exceed store-bought egg concentrations (<7–13 μg/kg; 3 % above detection limit) at soil lead concentrations >120 mg/kg and that the concentration in one of six eggs from a henhouse would exceed a 100 μg/kg guidance value at soil lead concentrations >410 mg/kg. Our models also suggested that the availability of dietary calcium supplements was another influential factor that reduced egg lead concentrations. Estimates of health risk from consuming eggs with the lead concentrations we measured generally were not significant. However, soil lead concentrations in this study were <600 mg/kg, and considerably higher concentrations are not uncommon. Efforts to reduce lead transfer to chicken eggs and associated exposure are recommended for urban chicken keepers.