Distribution, accumulation and depuration of administered lead in adult honeybees

In this study the Pb concentration in honeybees was determined by graphite furnace AAS after peroral administration of PbCl2. The Pb concentration, expressed on a dry weight base was determined in relation to the distribution over the body, the accumulation time, the clearance and the exposure dose. Pb is concentrated in the digestive system with the midgut accounting for 67% and the rectum for 27% of the accumulated metal. The barrier function of this system is thus corroborated in honeybees. Pb accumulation happens slowly in young bees which feed mainly on pollen; once they switch from pollen to nectar there is a sharp rise in their Pb content. After the 26th day a limit of tissue accumulation seems to be reached. Pb accumulation is equally efficient when the contamination starts at a forager age. Pb clearance is slower than expected; after 12 days only one third of the initial lead burden has been cleared. The Pb concentration in the animals increases significantly with the Pb concentration in the sugar syrup which they are fed, except at the highest dose of 50 mg/l. The possible use of honeybees as biomonitors for Pb pollution seems promising from these results.