Table 3.

Potential underestimation of radioactivity intake due to current sampling and exposure assessment protocols used in Western Australian mining operations.

Method/ Parameter	Default	Alternative	Factora	Uncertainty (GSD)
Dust sampling method	7-hole sample head	IOM sample headb	2.1	1.75
Airborne activity concentration adjustmentc	1	1.31	1.31	-d
Breathing rate	1.2 m3 h-1	1.5 m3 h-1	1.25	1.2
SEG meane	Geometric	Arithmetic	1.27	1.2
AMAD (µm)f	5	10	0.54	2.0
Total impact			2.3	2.5g

^aRefer text for discussion and derivation of each factor.

^bOr other sampler with sampling efficiency closely matching the ISO inhalable dust convention.

^cSpecifically for workplaces involving exposure to naturally occurring radionuclides, a correction factor is recommended for different samplers to minimise the potential for samplers to underestimate the inhaled activity (V.39, pp. 295–296, IAEA 2018). The factor of 1.3 is for an inhalable sampler used to sample aerosols with an AMAD of 10 µm.

^dThis factor is dependent on the particle size distribution (AMAD and GSD) of the aerosol, and the sampling efficiency of the PAS sample head.

^eAssuming SEG distribution GSD of 2 and using AM = GM × exp(½ (lnGSD)2).

^fBased on DCFinh (in mSv.Bq_ɑ⁻¹) for a NORM dust with a Th:U weight ratio of 10:1 (GWA 2023).

^gThe total uncertainty is given by: GSDtotal = exp(Vtotal)½, where Vtotal = Σ(ln GSDi)2. This assumes independent parameters and the uncertainties being lognormally distributed.