The Office of Science - What is Physics?

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DOE Physicists at Work

Profiles of representative DOE-sponsored physicists
doing research at universities and national laboratories

Compiled by the Office of Scientific and Technical Information

Naomi Harley

"I always tell my students to pick their Ph.D. topic carefully because you usually spend the rest of your life at it or something similar." So says Dr. Naomi Harley, professor with the New York University School of Medicine. Dr. Harley knows first hand the excitement of a career blossoming from the seeds of early training. While still in undergraduate school, she started working at the Health and Safety Laboratory (HASL), in New York City, learning how to measure the exposure to radioactive substances of Atomic Energy workers. That early research turned into a passion that evolved into a career dedicated to the physics of measuring and assessing human exposure.

"Radioactivity, especially naturally occurring radioactivity can be used as exquisitely sensitive tracers of substances in the air we breathe and also the water we drink," says Dr. Harley, who also serves on the Medical Isotopes committee at the NYU Medical Center. "We exploit these tracers to better understand how our environment can be improved. The result from these measurements determines the impact on peoples' health."

Of her early years at HASL, a Department of Energy prececessor facility, Dr. Harley says: "These were exciting times. We were learning how to measure the exposure of Atomic Energy workers to radioactive substances such as uranium, radium and radon. Yet there were no specific instruments to do this job."

New instrumentation was developed at HASL, and the research there quickly expanded.

"It was interesting for a young researcher to realize we were able to measure concentrations at atom levels - orders of magnitude below any other analytical technique," says Dr. Harley. "These early radioactivity measurements evolved into measuring fallout radioactivity from the nuclear weapons tests." The physics was dedicated to assessing human exposure, and volumes of research developed from these fallout years.

"For example, there was little known about meteorology, and fallout circling the globe and measured led to the current basic models of tropospheric and stratospheric circulation," says to Dr. Harley. "Also a great deal of biological information was uncovered using the very small quantities of fallout strontium 90 as a tracer from plants to diet to people."

After her early years at HASL, she enrolled in the nuclear engineering graduate program at NYU, always maintaining interest in physics dedicated to measurement and assessment of personal exposure. Her doctoral thesis was the first detailed model analysis of the bronchial airway dose from inhaled radon decay products dedicated to uranium miner lung dose and later to radon exposure in homes.

"The interest in measuring very low concentrations of pollutants persists today," says Dr. Harley. The thrust of her research has involved developing new passive instrumentation for personal exposure assessment during closure of a former uranium processing facility in Fernald, Ohio. The major exposure at Fernald is from the radioactive gas radon that is a decay product of the radium, and escapes into the air.

"We were very pleased to develop and patent a miniature 4-chamber passive detector (the 4Leaf) that measures both radio isotopes radon (radon-222) and thoron (radon-220). We also developed a miniature aerosol particle-size sample that runs with a small pump and measures the average particle size distribution inhaled, using the naturally occurring radioactive aerosols as tracers," says Dr. Harley. Particle size is the major factor in bronchial lung dose because the smaller the particle, the more likely to deposit in the lung airways.

"Although there are many conventional site monitors at Fernald to calculate worker dose, Fernald is the only DOE site with continuous particle-size data along with detailed radon and thoron measurements; products of this research," notes Dr. Harley. "So as the Fernald facility is remediated, our data exist to calculate very refined dose to the lung in these workers."

Development of inexpensive, usually passive instrumentation to measure very low levels of radioactivity that simply cannot be measured by other techniques, is still her passion.

"Although radioactivity is a known carcinogen, it is important to know accurately the radiation dose received in order to evaluate its risk," says Dr. Harley. "Our research is dedicated to this end."

Radium silo