Webinar - Silent Alpha: A Tale of Lost Emissions

Silent Alpha: A Tale of Lost Emissions

Presented by: Greg Hewson

Time: 

11:00 am AWST (Perth)
12:30 pm ACST (Darwin, Adelaide)
1:00 pm AEST (Brisbane, Sydney, Melbourne)

PRESENTER BIO – Greg Hewson

Greg is currently a doctoral researcher at Edith Cowan University focussing on radiation research in the mining industry with an emphasis on intake of naturally occurring radionuclides. Previously, Greg’s career involved global and executive health and safety roles for over 15 years, where he provided technical expertise, coaching and leadership for major projects across multiple business sectors, geographies and cultures. Before his corporate career, Greg was a senior leader in the Western Australian Mines Safety Inspectorate and was involved in several major research studies and international consulting assignments relating to occupational exposures in mining operations.

ABSTRACT

Workers employed in some mineral processing operations are at risk of inhaling dust that contains naturally occurring radioactive material (NORM). Traditionally, internal dose assessments are based on the application of dosimetric and biokinetic models to intakes derived from personal air sampling (PAS). Recent research shows that, for decades, radiation dose from intake of dust in some mining operations has been underestimated, perhaps by a factor of four. This is partly because the PAS and analysis protocols currently used don’t capture the airborne alpha activity that workers actually inhale.

In this webinar, historical thorium intakes for mineral sand workers estimated from PAS are compared with values obtained from past bioassay measurement, such as urinary and faecal thorium excretion, in-vivo lung counting, and exhaled thoron (220Rn) in breath. Intakes derived from bioassay are consistently greater than those derived from PAS. Contributing factors include sensitivity to model input parameters, biases in particle size selection by PAS equipment, alpha self-absorption on dust-laden PAS filters, and the use of poorly defined similar exposure groups (SEGs). Consequently, both past and current internal dose estimates based on alpha activity measurements are likely substantially higher than reported.

Practical guidance will be provided to improve PAS-derived intake estimates, including applying correction factors to adjust for dust sampler efficiency and alpha particle self-absorption, and adopting the most realistic model input parameters such as breathing rate and mode, and workplace-specific dust characteristics like particle size and solubility.