New ICRP Recommendations on Radon Abel J. González Vice-President of ICRP Thiagan Pather National Nuclear Regulator
Radon 50% World population radiation doses Proven lung carcinogen Until recently studies of miners formed main basis for estimating risks from radon Recent case-control studies of residential radon now provide direct estimates of radon risk Two recent important international consensus UNSCEAR 2006, Annex E, estimates on radon WHO 2009 International Radon Project ICRP Radon Statement (Nov 2009)
Issues • Risks • Converting physical radon quantities (e.g. activity per unit volume or potential energy over time) into radiation protection quantities. (e.g. effective dose) • Protection of workers • What workers to protect and how • Protecting members of the public.
UNSCEAR 2006 ANNEX ESources-to-Effects assessment for radon in homes andworkplaces • Sources and Levels • Dosimetry • Experimental Studies • Epidemiological Studies of Miners • Epidemiological Studies of Residential Exposure • Effects of Radon on Organs and Tissues other than Lung • Implications for Risk Assessment S
UNSCEAR • The excess relative risk from long-term residential exposure to radon at 100 Bq m-3 is about 0.16 with about a three-fold factor of uncertainty higher or lower than that value. • Because of the synergistic interaction between the effects of radon exposure and those of inhalation of tobacco smoke, smokers account for nearly 90 per cent of the population-averaged risk from residential exposure to radon.
WHO • Recent studies cancer provide strong evidence that indoor radon causes a substantial number of lung cancers in the general population. • They indicate that the lung cancer risk increases proportionally with increasing radon exposure. • The proportion of lung cancers attributable to radon range from 3 to 14%. Radon is the second cause of lung cancer after smoking. • Most of the radon-induced lung cancer cases occur among smokers due to a strong combined effect of smoking and radon.
WHO • In view of the latest scientific data, WHO proposes a reference level of 100 Bq/m3. However, if this level cannot be reached under the prevailing country-specific conditions, the chosen level should not exceed 300 Bq/m3 which represents approximately 10 mSv per year. • A national reference level for radon should represents the maximum accepted radon concentration in a residential dwelling. For homes with radon concentrations above them remedial actions may be recommended or required.
Risk of lung cancer relative to lifelong non-smokers(After Darby et.al., Br Med J (www.bmj.com) Usual radon (Bq/m3)
Cumulative absolute risk of lung cancer deathby age 75 (after Darby et. al) Usual radon (Bq/m3)
Smoking is Main Cause of LungCancer • Darby et al (2005) in a study of 13 European residential case control studies looked at combined effect of smoking and residential radon on the absolute risk of lung cancer and found that for lifetime (75y) of exposure to 100 Bq m-3 and using the same relative risk factor of 0.16 per 100 Bq m-3: • 0.47% risk from radon to never smokers • 11.6% risk from radon to smokers
International Commission on Radiological Protection Statement on Radon Approved by the Commission in Porto on November 2009
The Commission had previously issued recommendations for protection against radon-222 at home and at work ICRP Publication 65. • The Commission issued revised recommendations for a system of radiological protection in ICRP103
The Commission has reviewed new scientific information on the health effects due to radon. • As a result of this review, the Commission now recommends a detriment-adjusted nominal risk coefficient for a population of all ages of 8x10-10 per Bq h m-3 for exposure to radon-222 gas in equilibrium with its progeny (i.e. 5x10-4 WLM-1)*. *) The Commission’s findings are consistent with other comprehensive estimates of UNSCEAR and WHO.
Following from the 2007 Recommendations, the Commission will publish revised dose coefficients for the inhalation and ingestion of radionuclides. • The same approach will be applied to intakes of radon and progeny as that applied to other radionuclides. • The new dose coefficients will replace the Publication 65 dose conversion convention which is based on nominal values derived from epidemiological studies. • The current dose conversion values may continue to be used until the new dose coefficients are available. • The Commission advises that the change is likely to result in an increase in effective dose per unit exposure of around a factor of two.
The Commission reaffirms that radon exposure in dwellings due to unmodified concentrations of radium-226 in the earth’s crust, or from past practices not conducted within the Commission’s system of protection, should be treated as an existing exposure situation. • The Commission’s protection policy for these situations continues to be based on setting a level of annual dose of around 10 mSv from radon where action would almost certainly be warranted to reduce exposure. • Taking account of the new findings, the Commission has therefore revised the upper value for the reference level for radon gas in dwellings from 600 Bq m-3 to 300 Bq m-3. • National authorities should consider setting lower reference levels according to local circumstances. • All reasonable efforts should be made, using the principle of optimization of protection, to reduce radon exposures to below the national reference level.
Taking account of differences in the lengths of time spent in homes and workplaces (about a factor of three), a level of radon gas of around 1000 Bq m-3 should define the entry point for applying occupational protection requirements for existing exposure situations. • The international value of 1000 Bq m-3 might be used globally (in the interest of international harmonization of occupational safety standards), as the entry point for applying occupational radiological protection requirements in existing exposure situations. The situation will then be managed as an occupational exposure situation.
Exposure to radon in dwellings and exposure to radon in workplaces in which the exposure is not qualified as occupational exposure shall be regarded as an existing exposure situation and controlled through the use of a reference level and optimization of radiation protection. • For dwellings and other buildings with high occupancy rates by the public, the reference level shall not normally exceed an average radon concentration of 300 Bq m-3 y-1. • (However, in special circumstances where extreme local conditions require flexibility a higher value of reference level may be used.)
Exposure of workers to radon in workplaces shall be considered to be an occupational (and therefore a planned) exposure situation subject to the relevant occupational requirements, if: • the exposure in the workplace, whatever its level, is required by, or is directly related to, the work in the workplace, or, • the exposure in the workplace is not required by or is not directly related to the work in the workplace, but cannot be reduced below the reference level to be established by the regulatory body, which shall not be higher than an average radon concentration of 1000 Bq m-3 y-1 in the workplace
Exposure to radon in workplaces, which is required by, or is directly related to, the work in the workplace(non adventitious)
Uranium yes Coal why not?
Workplace radon exposures are not limited to uranium mining • Other mining with potential exposures to elevated radon include: gold, phosphate, tantalum, titanium, niobium, vanadium, fluorspar etc. • UNSCEAR 2000 provides information on levels of uranium and thorium in various minerals • Limited data on radon (thoron) exposures in none uranium mines and workplaces but in some instances can be appreciable (several WLM/y)
Exposure to radon in workplaces, which is not required by, or is not directly related to, the work in the workplace(adventitious exposure)
What adventitious exposure is occupational exposure? • All? entry level = 0 Bq/m3 • None? entry level = Bq/m3 • Only those that may justify action? entry level = ? 1000 Bq/m3 is a defensible entry level!
Important policy decision While recognising and accepting the scientific evidence that active smokers are at a much higher risk from radon than non-smokers or ex-smokers, should judge as appropriate to establish radon-related radiation protection requirements on the basis of a single nominal risk co-efficient for a population of all ages that includes smokers, ex-smokers and non-smokers?
Smoking prevalence changes world-wide Developed countries: • Increases among women in some, reduction in other countries • Reduction among men Developing/newly industrialized countries: • Prevalence increases in both sexes • Dynamics differ
ICRP Main Commission Meeting 2010 April 13-15 Suzhou, China • Approval of ICRP TG 64 report "Lung Cancer Risk from Alpha Emitters” for public consultation in conjunction with the previously approved ICRP Statement on Radon (Preston) • Approval of ICRP DOCAL report “Dose Conversion Coefficients for External Radiation Sources” for publication without public consultation (Menzel)
JOINT RASSC/WASSC WORKING GROUP • To review the requirements in draft 2.5 of the BSS relating to radon and, taking into account the recent statement from the ICRP, identify any changes that might be necessary. • Members: • Mr. S. Chandler (WASSC – United Kingdom); • Mr. C. Clement (ICRP); • Mr. D. Howard (WASSC – Canada); • Mr. P. Johnston (WASSC – Australia); • Mr. J.-F. Lecomte (RASSC – France); • Mr. M. Markkanen (RASSC – Finland); • Ms. M. Perez (WHO); • Ms. E. Rochedo (RASSC – Brazil); • Mr. H. Yonehara (RASSC – Japan); • Mr. T. Colgan (IAEA Secretariat).
The Working Group noted that radon is mentioned in requirements 1.39, 3.4(c), 3.4(d), 5.1(c)(i), 5.19, 5.20, 5.21, 5.27, 5.28, 5.29 (including related footnotes 48 - 50 and 52 - 53), and Schedule III-8 and its associated Table III-1.
For radon exposure in workplaces that are regarded as existing exposure situations, the current BSS requires the regulatory body or other relevant authority to set a reference level which does not exceed a maximum annual average concentration of 1500 Bq/m3. Where radon concentrations remain above 1000 Bq/m3, exposure to radon, along with any other worker exposures, are to be subject to the relevant requirements for occupational exposure in planned exposure situations. The use of two different values causes confusion and is unnecessary. For radon exposures in workplaces that fall into the category of existing exposure situations, it was considered appropriate, in line with the recent ICRP statement, that the regulatory body or other relevant authority shall set a reference level which does not exceed a maximum annual average concentration of 1000 Bq/m3. Where it is not possible to reduce radon concentrations below the established reference level, the regulatory body should have flexibility to decide how to deal with these exposures i.e. the concept of an “entry point” to planned exposure situations should be deleted.
Exposure to radon in planned exposure situations such as uranium mines needs to be assessed regardless of whether or not it is above or below the reference level. Such exposure needs to be included in the calculation of an individual’s dose for compliance with dose limits. In other planned exposure situations, such as workplaces where sealed sources are used, exposure to radon is considered as an existing exposure situation and is subject to the requirements related to the reference level; such exposure is not assessed for compliance with dose limits. For radon exposures in dwellings, it was considered appropriate, in line with the recent ICRP statement, that the regulatory body or other relevant authority shall set a reference level which does not exceed a maximum annual average concentration of 300 Bq/m3.
The reference level for dwellings should also be applied to other buildings with a high occupancy rate by the public i.e. schools, prisons, nursing homes etc. • Footnotes should be added to clarify the relationship between the chosen reference levels and dose, indicating the assumptions made in the calculation (i.e. equilibrium factor, occupancy rate etc.) • As dose conversion co-efficients for radon and radon progeny are unlikely to be published by the ICRP prior to approval of the BSS, a decision will be required on retention, deletion or modification of the values currently listed in Schedule III, Table III-1.
TECHNICAL MEETING ON REVISION OF THE BSSNewest Recommendations on Health effects from Radon15-16 December 2009 • As in all requirements standards, the language to be used in establishing radon-related requirements should be regulatory rather than tutorial, indicating unambiguously what is acceptable and what is not. However, giving the unique characteristics and ubiquity of radon exposure situations, it is important that the language allows for some flexibility to reflect the range of conditions that apply in different situations. • The BSS should contain separate requirements for both public and occupational radiation protection and a clear distinction should be made between the different quantities applied. In the case of occupational exposure, this is the total effective dose incurred by workers while at work. In the case of public exposures, it is the additional effective dose attributable to a particular source.
In both planned and existing exposure situations it is appropriate to define requirements in terms of activity concentration of radon in dwellings and workplaces. Exposure of workers to radon in workplaces shall be considered to be occupational exposure (and therefore a planned exposure situation) and subject to the relevant occupational exposure requirements, if: the exposure in the workplace, whatever its level, is required by, or is directly related to, the work in the workplace1, or the exposure in the workplace is not required by or is not directly related to the work in the workplace, but cannot be reduced below the reference level to be established by the regulatory body for the purpose of reducing the exposure level in the workplace through optimizing radiation protection; the value chosen for the reference level shall not be higher than an average radon concentration of 1000 Bq m-3 y-1 in the workplace2. 1 For example, exposure of miners and of workers at spas 2 This is the entry-level into the occupational protection regime established for these types of exposures in current international standards as recommended by the International Commission on Radiological Protection for the purpose of intergovernmental harmonization