I am a Professor in the Department of Physics and Astronomy at McMaster University. My research program is to build biomedical devices for painless, low risk, assessment of toxic metals in people. I study elements including lead (Pb), arsenic (As), fluorine (F), aluminum (Al). The biomedical devices measure either levels of the toxin in organs such as kidneys that may be at risk, or measure retention in bone or liver which can be a measure of long term or chronic exposure. I have studied lead (Pb) exposure for over 25 years, and by using x-ray techniques to measure the bone Pb content of women smelter workers, found previously unknown effects of lead on women's health. Recently, my group build the world's first device for the in vivo measurement of fluorine in bone and demonstrated that in Ontario, tea drinking is a significant exposure factor. Currently, we are developing a system to measure gadolinium (Gd) in bone and have shown that some small, potentially toxic, portion of administered MRI imaging enhancing drugs remains in people's bones for years after the scan.