Assessment and Management of Cancer Risks from Radiological and Chemical Hazards Assessment and Management of Cancer Risks from Radiological and Chemical Hazards

A Joint Working Group was established in April 1995 by the President of the Atomic Energy Control Board (AECB) and the Assistant Deputy Minister of the Health Protection Branch of Health Canada to examine the similarities, disparities and inconsistencies between the levels of risk considered acceptable for regulating ionizing radiation and those considered acceptable for regulating chemical and microbiological hazards. During the process of collecting, analyzing and interpreting information, the Joint Working Group realized that its terms of reference as written presented a major difficulty because of the lack of consensus on acceptable levels of risk. Consequently it decided that the most reasonable way to proceed was to compare the risk assessment and management processes used to protect the public from radiation, chemicals and microbiological hazards. This report concentrates on the assessment and management of ionizing radiation and genotoxic chemicals (which both cause cancer by damaging the DNA in cells) and pays less attention to non-genotoxic effects and microbiological hazards. The report also examines public more than occupational exposures and exposures from man-made rather than naturally occurring agents. Risk assessment methods for ionizing radiation and genotoxic chemicals are well-developed and generally similar in principle. Both depend upon the establishment of doseresponse relationships, and prudently assume linearity with no threshold dose. However, there are often differences in the type of data used, the range over which dose-response relationships are characterized, the identification of organand speciesspecific differences to carcinogenic effects, and consideration of the effects of combined exposures. Risk management strategies for both ionizing radiation and genotoxic chemicals are also well-developed and are similar in that they both set legal limits to exposures, endorse the ALARA principle, and employ approaches such as source controls, point-of-use controls, and education. However, the ALARA principle is applied in different ways for radiation and chemicals. While its formal application is more fully developed in radiation protection, it is not applied in a completely systematic manner in either area. Recognizing that actual levels of exposure are, in general, well below legal limits and guidelines and that observable health effects are largely absent based on current epidemiological methodologies at these exposure levels, the Joint Working Group finds that the risk management strategies for regulated practices for both radiation and genotoxic chemicals provide a high degree of health protection. It is not possible to determine whether environmental exposures to ionizing radiation or genotoxic chemical carcinogens pose the greater risk of cancer at this time. The consensus of the Joint Working Group is that it does not appear fruitful at this time to consider harmonizing the regulation of ionizing radiation and genotoxic chemicals; however, future opportunities should be considered. In doing so, consideration must be given as to whether public health benefits would be derived from harmonization. Further, discussions should take place in a broader context in which all relevant public health concerns are addressed. For example, in addition to ionizing radiation and genotoxic chemicals, the impact of microbiological agents on public health should be considered.