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Mỹ cơ quan quản lý sử dụng không có ngưỡng tuyến tính (LNT) lý thuyết làm cơ sở cho dự toán rủi ro và ra quyết định quy định. Trong tiếp cận đánh giá rủi ro theo cách này, hai vấn đề ngay lập tức xuất hiện. Trước tiên, có không nói chung đã thỏa thuận nguyên tắc có thể được sử dụng để chọn một lý thuyết tiên đoán loại trừ sinh học do chính đáng khác alternatives.1 Như đã chỉ ra trong chương 2 và sau đó trong chương này, lựa chọn lý thuyết là được thúc đẩy. | 3 No Safe Dose U.S. regulatory agencies use the linear no-threshold LNT theory as a basis for risk estimation and regulatory decision making. In approaching risk assessment in this way two problems immediately emerge. First there is no generally agreed-upon principles that can be used to select one predictive theory to the exclusion of other biologically plausible alternatives.1 As pointed out in Chapter 2 and later in this chapter theory selection is driven by the need for simplicity and for conservative risk predictions. However the simplest and most conservative theory may not necessarily be the most desirable because of the limited range of predictions that can be made. Complex theories with several parameters offer a wider range of predic-tions.2 Second theoretical risk predictions at environmental or occupational exposure levels preclude meaningful decision making because risk uncertainties are so large. The problem of uncertainty in decision making is discussed in Chapter 4. Chapter 2 discusses several theories that could be used in regulatory decision making but LNT is preferred by standards-setting organizations because it is simple to use and has biological plausibility. In the 1970s the U.S Environmental Protection Agency EPA considered a number of models and theories as a basis for risk quantification but selected LNT theory because there was a successful track record in its utility. The old Atomic Energy Commission the predecessor organization to the U.S. Nuclear Regulatory Commission U.S. NRC had successfully used LNT theory in quantifying risks of cancer from exposure to radioactive strontium and radioactive iodine fallout from atmospheric nuclear weapons testing. Compared to most other plausible alternatives LNT provides a conservative estimate of risk. If an agency is wrong using an LNT-derived risk estimate it is likely to be wrong on the safe side by overestimating risk. Alternative theories e.g. theories that predict a threshold provide a less .
