Lead shot contribution to blood lead of First Nations people: The use of lead isotopes to identify the source of exposure

Although lead isotope ratios have been used to identify lead ammunition (lead shotshell pellets and bullets) as a source of exposure for FirstNations people of Canada, the actual source of lead exposure needs to be further clarified.Whole blood samples for First Nations people of Ontario, Canada, were collected from participants prior to the traditional spring harvest of water birds, as well as post-harvest. Blood-lead levels and stable lead isotope ratios prior to, and after the harvest were determined by ICP-MS. Data were analyzed by paired t-tests and Wilcoxon Signed-Ranks tests. All participants consumed water birds harvested with lead shotshell during the period of study. For the group excluding six males who were potentially exposed to other sources of lead (as revealed through a questionnaire), paired t-tests and Wilcoxon Signed-Ranks tests showed consistent results: significant (pb0.05) increases in blood-lead concentrations and blood levels of 206Pb/204Pb and 206Pb/207Pb towards the mean values we previously reported for lead shotshell pellets; and a significant decrease in 208Pb/206Pb values towards the mean for lead shotshell pellets. However, when we categorized the group further into a group that did not use firearms and did not eat any other traditional foods harvested with lead ammunition other than waterfowl, our predictions for 206Pb/204Pb, 206Pb/207Pb and 208Pb/206Pb hold true, but therewas not a significant increase in blood-lead level after the hunt. It appears that the activity of hunting (i.e., use of a shotgun) was also an important route of lead exposure. The banning of lead shotshell for all game hunting would eliminate a source of environmental lead for all peoplewho use firearms and/or eat wild game.