X-Ray Exposé

McMaster University Professor Fiona McNeill’s research is redefining safe levels of chemical exposure.

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Lead was one of the first metals to be mined, and it has been used widely since then – including in paint, pipes, and gasoline. However, there is a global push to lower levels of lead exposure because we know that high levels of lead impact human health. Notably, this includes decreased IQ in children.

In Canada, lead has been removed from gasoline and paint, and levels have been reduced in our drinking water, cutting our exposure to less than half of what it was 20-25 years ago.

To help define safe limits, Fiona McNeill, professor of medical physics and applied radiation sciences at McMaster University, is measuring long-term metal exposure and its impact on human health.

“At the moment, we assess people’s exposure through measurements of blood in urine, but they only tell us about a person’s recent exposure and we know that most health effects are consequence of long-term exposure,” explains McNeill. “Using radiation-based techniques – mostly x-ray techniques – I assess people’s exposure painlessly and simply.”

This technology is portable, allowing McNeill to study at-risk populations all over the world.

The case for fluoride is more complex. While lead reduction is a clear goal, we choose to add fluoride to our drinking water as a public health benefit, mainly for its protective effect on teeth. However, at high exposures, there is increased risk of bone fracture. Finding the right amount to achieve dental health and avoid fracture risks is important. McNeill is now working on defining safe levels by measuring fluoride non-invasively.

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Prof. Fiona E McNeill obtained a B.Sc. (1986) in physics from the University of Edinburgh, Scotland and a Ph.D. (1989) in physics from the University of Birmingham, England. In 1990, she spent a year at the Lund University Radiophysics Institute in Malmö, Sweden, on a Royal Society European Science Exchange Fellowship. She then spent four years in the Toxicology Program of the University of Maryland, before joining the Department in 1995. Prof. McNeill’s research has been in the development and application of techniques for the measurement of elements in vivo. Prof. McNeill’s work has been largely cross-sectional studies of lead exposure using x-ray fluorescence (XRF) bone lead measurements, which provide a painless non-invasive marker of long term lead exposure. The measurements have been used to study populations of occupationally exposed workers and environmentally exposed subjects and have investigated the possible neuropsychological effects of lead. In addition to applying the techniques, Prof. McNeill has been involved with graduate students in the development of systems to measure toxic elements. Ana Pejovic-Milic (Ph.D. candidate) has been developing neutron activation measurement of aluminum; there is a controversial connection of aluminum exposure to dementia. Dr. Joanne O’ Meara (Ph.D. 1999) developed uranium measurements as a possible method of assessing Persian Gulf War verteran’s exposure. Prof. McNeill’s current research work is the development of accelerator based systems; improved NAA methods for the measurement of cadmium, mercury and aluminum are being developed. However, research into essential elements is also being studied. Michelle Arnold (Ph.D. candidate) has been assessing the feasibility of measuring manganese in vivo. Manganese is an essential element which can, however, be toxic in large doses and is associated with Parkinson’s like symptoms.