In vivo x-ray fluorescence of bone lead in the study of human lead metabolism in a cohort of the general population and smelter employees

Abstract

<p>After developing the clover-leaf geometry system, the system was used for the first time in a major survey in 2008 to measure the lead levels of 497 smelter employees in the province of New Brunswick in Canada, who participated in a lead study during the time interval of 14 January to 6 March 2008. Participants were measured for lead concentration in the left tibia and right calcaneus, each for 30 min. The minimum detection limit (MDL) of the clover leaf geometry detector system was improved by a factor 3.1 compared to a conventional system. Improvement of the detection system makes low-level environmental lead exposure studies relating to public health possible. This is important because low-level lead exposure has been well known to have many adverse health effects. Also, since the delivered effective dose is small (50 nSv), the technique can be used to measure the bone lead of sensitive populations such as the elderly and children. A total of 263 of individuals participated in a pilot study of bone and blood lead measurements supported by Health Canada’s Chemical Management Plan. The study was conducted in collaboration with McMaster University and St. Joseph’s Health Centre located in Toronto. Participants were measured for bone lead (calcaneus and tibia) concentration and whole blood and serum lead levels. Among participants 17 (6.5%) of them were 1 to 5 years old; 37 (14%) of them 6 to 10; 44 (17%) of them 11 to 19; 47 (18%) of them 20 to 35; 36 (14%) of them 36 to 50; 46 (17.5%) of them 51 to 64, and finally 19 (7%) of them belonged to age range of 65 to 85 years old. v In most of the previous work, the relationship between bone lead concentration and Cumulative Blood Lead Index (CBLI) was considered to be linear. In the study of a cohort of smetler employees we observed a non- linear relationship between CBLI and bone lead contents. The study showed that for the higher values of CBLI (earlier hired smelter employees), the tranfer rate of lead from blood to bone becomes more efficient. Oppositly, we obsrved that for a higher levels of CBLI, the transfer rate of lead from bone to blood is less efficient and lead stays in bone longer. In this study, for the first time the transfer rate of lead from bone to blood was estimated as a funtion of predictors including age, employment time, and body lead contents for smelter employees.</p>