Eyeglass lenses for personal radon dosimetry

Eyeglass lenses are commonly composed of allyl-diglycol carbonate (CR-39), an alpha-particle detecting plastic, thus making such lenses personal radon dosimeters. Samples of such lenses have been etched to reveal that radon and radon progeny alpha tracks can be seen in abundance, and sensitivities have been calibrated in radon chambers as a primary calibration and with a uranium-based source of alpha particles as a convenient secondary standard. Natural, environmental (fossil) track densities ranged from 3,000 to 25,000 cm(-2) for eyeglasses that had been worn for various times from 1 to nearly 5 y. Average radon concentrations to which the wearers were exposed are inferred to be in the range 20 to 130 Bq m(-3) (0.5 to 3.5 pCi L(-1)). Procedures for consistent, meaningful readout are described.