Hazards, chemical radiation

Determining occupational exposnres (e.g., hazardous chemicals, radiation, noise, biological agents, heat)... 

The best use of doUar resources will determine the best approach to the effective use of the money available. Programs that may require sampling are hazardous chemicals, radiation, and noise. If new chemicals are to be put to use, this may require more sampling than previously. If OSHA citations have been issued then more sampling may be necessary to maintain compliance. The presence of hazardous waste may require training in spill containment and remediation as well as contracts for disposal and spill cleanup or remediation. The health issues involved in the company s operation may result in special types of personal protective equipment being needed and purchases. Training will be needed on the use of the equipment, which is a cost factor in loss of production and time and must be accounted for. 

This Report presents recommendations of the National Council on Radiation Protection and Measurements (NCRP) on a new system for classifying waste that contains hazardous substances, either radionuclides or hazardous chemicals. NCRP s recommendations incorporate three principles. 

The primary purpose of this Report is to present NCRP s recommendations on classification of hazardous wastes. The Report is directed at a multidisciplinary audience with different levels of technical understanding in the fields of radiation and chemical risk assessment and radioactive and chemical waste management. Anew hazardous waste classification system is proposed that differs from the existing classification systems for radioactive and hazardous chemical wastes in two fundamental respects. First, hazardous waste would be classified based on considerations of health risks to the public that arise from disposal of waste. Hazardous waste would not be classified based, for example, on its source. Second, the classification system would apply to any hazardous waste, and separate classification systems for radioactive and hazardous chemical wastes would not be retained. In the proposed system, waste would be classified based only on its properties, and the same rules would apply in classifying all hazardous wastes. 

Similar considerations apply to the discussions of approaches to risk management in Section 3.3. Readers who are knowledgeable about principles of radiation protection may not be familiar with the different approach to health protection used for hazardous chemicals, and vice versa, and an understanding and resolution of the different approaches to risk management is important in developing a comprehensive and risk-based waste classification system. 

Chemical hazard identification. In contrast to radiation, most chemicals are thought not to be hazardous to human health at a sufficiently low dose. In the United States, the process of determining whether a chemical is hazardous relies upon principles established by EPA. These principles are used extensively, but not universally, in other countries. This Section describes the general principles used by EPA to identify hazardous chemicals. Hazard identification is related to the process of dose-response assessment for hazardous chemicals discussed in Section 3.2.1. 

Given the models for estimating external or internal radiation doses in specific organs or tissues, the following sections consider the responses resulting from a given dose by any route of exposure. As is the case with hazardous chemicals, both stochastic and deterministic radiation effects can occur. 

In spite of uncertainties in the dose-response relationship for radiation discussed above, it is generally believed that radiation risks in humans can be assessed with considerably greater confidence than risks from exposure to most hazardous chemicals that cause stochastic effects. The state of knowledge of radiation risks in humans compared with risks from exposure to chemicals that cause stochastic effects is discussed further in Section 4.4.2. 

First, the threshold for hazardous chemicals that cause deterministic effects is assumed for purposes of health protection to represent a lower confidence limit, taking into account uncertainties in the dose-response relationship (see Section 3.2.1.2.7). Depending, for example, on the slope of the dose-response relationship near the threshold, the chosen steps in the dosing regimen, and the magnitude of uncertainties in the data, the lower confidence limit of the assumed threshold can be substantially below MLE. In radiation protection, the estimated thresholds for deterministic effects are based on MLEs of dose-response relationships (ICRP, 1991). 

Based on these differences, the use of RfDs for hazardous chemicals that induce deterministic effects to define acceptable exposures of the public often may be considerably more conservative (provide a substantially larger margin of safety) than the dose limits for radiation induced deterministic effects. The likely degree of conservatism embodied in RfDs has important implications for establishing limits on allowable exposures to substances causing deterministic effects for the purpose of developing a risk-based waste classification system. Dose limits for deterministic effects for radiation should not be important in classifying waste (see Section 3.2.2.1). 

The different approaches to management of stochastic risks for radionuclides and hazardous chemicals are referred to in this Report as the radiation and chemical paradigms (EPA, 1992a). The following discussion of the two paradigms for management of stochastic risks is adapted from previous papers (Kocher, 1999 Kocher and Hoffman, 1991). 

The chemical paradigm also differs from the radiation paradigm in that there are no standards that apply to all controlled sources of exposure and all hazardous substances combined, as in radiation protection standards. Regulations for hazardous chemicals generally apply only to specific release pathways (eg., the atmosphere) or... 

In setting limits on exposure intended to prevent the occurrence of deterministic responses, the safety and uncertainty factors that are applied to the assumed thresholds for hazardous chemicals that cause deterministic effects usually are considerably larger (by at least a factor of 10) than the safety factor normally applied to the thresholds for deterministic responses from exposure to radiation. Furthermore, the assumed threshold usually is more conservative for hazardous chemicals than for radiation (i.e., a lower confidence limit of the threshold often is used for... 

The primary measure of stochastic responses for radionuclides used in radiation protection has been fatalities, whereas incidence is the universal measure of stochastic responses for hazardous chemicals. 

Previous sections have presented technical and historical information on radiation and chemical risk assessment and on classification of radioactive and hazardous chemical wastes. This information provides important perspectives for establishing the foundations of a new hazardous waste classification system. Before establishing these foundations, it is useful to specify the attributes that an ideal waste classification system should possess. The following sections identify the desirable attributes of a waste classification system including that the system should be risk-based, it should allow for exemption of waste, and it should be comprehensive, consistent, intrinsic, comprehensible, quantitative, compatible with existing systems, and flexible. These attributes should be recognized as goals that are not all likely to be fully realized in a practical waste classification system. 

For the purpose of developing a risk-based hazardous waste classification system, prevention of deterministic responses should be of concern only for hazardous chemicals, but not for radionuclides. Deterministic responses from exposure to radionuclides can be ignored because radiation dose limits for the public intended to limit the occurrence of stochastic responses are sufficiently low that the doses in any organ or tissue would be well below the thresholds for deterministic responses (see Section 3.2.2.1). 

Fatalities. In the second option, the common measure of stochastic response from exposure to radionuclides and hazardous chemicals would be fatalities, without any modifications to account for such factors as differences in lethality fractions for responses in different organs or tissues or expected years of life lost per fatality. This option is particularly advantageous for radionuclides, because fatalities is the measure of response provided by the most scientifically defensible database on stochastic radiation effects in humans. Fatalities is the measure of response normally emphasized in radiation risk assessments. 

However, given the current state of knowledge and methods of dose-response assessment for substances that cause stochastic responses, there appear to be important technical and institutional impediments to the use of either incidence or fatalities exclusively. Data on radiation-induced cancer incidence and chemical-induced cancer fatalities for use at the low doses and dose rates relevant to health protection are not readily available, and current regulatory guidance calls for calculation of cancer incidence for hazardous chemicals. Since use of a common measure of response for all substances that cause stochastic responses may not be practical in the near term, both measures (fatalities for radionuclides and incidence for hazardous chemicals) could be used in the interest of expediency. The primary advantage of this approach is that the measures of stochastic response for radionuclides and hazardous chemicals would be based on the best available information from studies in humans and animals, and it would involve the fewest subjective modifying factors. This approach also would be the easiest to implement. 

A risk-based waste classification system should include explicitly justified degrees of conservatism in protecting public health. Differences in the meanings of commonly used terms between the radiation and hazardous chemical communities presently... 

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