ICRP issues statement lowering threshold for eye lens

There have been a number of reports in recent years indicating prevalence of opacities in the eyes of staff exposed to radiation levels below the thresholds as established by the ICRP (ICRP Publication 60 of 1990 and ICRP Publication 103 of 2007). The values for detectable lens opacities are:  5 Sv for protracted and 0.5-2.0 Sv for brief exposure. The 2007 ICRP report stated “However, new data on the radiosensitivity of the eye with regard to visual impairment are expected”, and concluded “Because of the uncertainty concerning this risk, there should be particular emphasis on optimization in situations of exposure of the eyes”.

The Commission has now reviewed recent epidemiological evidence and has issued a statement after its meeting on 21st April 2011.

According to this statement, the threshold in absorbed dose for the lens of the eye is now considered to be 0.5 Gy.

Further , for occupational exposure in planned exposure situations the Commission now recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv.

The Commission continues to recommend that optimisation of protection be applied in all exposure situations and for all categories of exposure. With the recent evidence, the Commission further emphasises that protection should be optimised not only for whole body exposures, but also for exposures to specific tissues, particularly the lens of the eye, and to the heart and the cerebrovascular system.

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